SYSTEM OF

CANE SUGAR FACTORY

CONTROL

SECOND EDITION

INTERNATIONAL SOCIETY OF SUGAR CANE TECHNOLOGISTS

SPECIAL COMMITTEE ON UNIFORMITY IN REPORTING FACTORY DATA

1955

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SYSTEM OF

CANE SUGAR F A C T O R Y

C O N T R O L

SECOND EDITION Edited by J. L. CLAYTON

Gardens Point A22810773B System of cane sugar factory control

INTERNATIONAL SOCIETY OF SUGAR CANE TECHNOLOGISTS

SPECIAL COMMITTEE ON UNIFORMITY IN REPORTING FACTORY DATA

N. J. KING, Chairman

1955

Wholly set up and printed in Australia by WATSON, FERGUSON AND COMPANY

Brisbane, Q. 1955

Registered in Australia for transmission by Post as a Book.

PREFACE TO THE SECOND EDITION

When the Committee on Uniformity in Reporting Factory Data met during the Eighth Congress in British West Indies in 1953, one of its resolutions was that the booklet "System of Cane Sugar Factory Control of the I.S.S.C.T." be "brought up to date and repr in ted" .

On the same occasion the resignation of Dr. F. W. Zerban as Chairman of the Committee was accepted w i th regret, and the wr i te r was appointed to that office, w i th Mr. J. L. Clayton as Secretary. The major portion of Dr. Zerban's excellent composition in the original booklet remains unchanged in the new edit ion, the preparation of which is due to Mr. Clayton.

The question of bringing the booklet " up to date" has occasioned con­siderable thought. Certain revisions had been approved by the Committee as a body but others arose for consideration and it was a question whether they should be included wi thout formal approval. The policy adopted was to select those items which needed revision but were not of a highly contentious nature and to submit proposals to the regional sub-committees. The response was gratifying, the proposals being either approved or commented upon in con­structive manner. Our thanks are due to the members of the sub-committee who assisted.

In the current edition two appendices have been included. The first presents data on the units employed in various countries and deals extensively wi th English-Metric conversions. The second deals w i th the Tables used in sugar technology. Though there were several requests for the publication of standard Tables it was decided not to print these, for reasons explained in Appendix II.

Thanks are due to the Queensland Society of Sugar Cane Technologists, which body has undertaken the financial responsibility for the printing of this booklet.

It is hoped that the current edition wi l l prove a worthy successor to the first and that its publication wi l l serve to further the good work of the Committee.

NORMAN J. KING,

Chairman.

PREFACE TO THE FIRST EDITION HISTORY A N D AIMS OF T H E COMMITTEE

The Special Committee on Uniformity in Reporting Factory Data was created at the Second Conference of the Society, held at Havana in 1927, upon motion made by M. A. del Valle, who pointed out that the confusion of terms used in sugar factory reports, and the multiplicity of control methods employed made it impossible fairly to judge the results obtained and to make mutual comparisons. He urged a study of this question and the establishment of uniform methods by common consent.

The Committee members appointed at the beginning were M. A. del Valle (Puerto Rico), P. C. Tarleton (Cuba), and F.W. Zerban (U.S.A.), chairman. At the Third Conference (Soerabaja, Java, 1929) E. C. von Pritzelwitz van der Horst (Java) was appointed, vice P. C. Tarleton; he resigned prior to the Fifth Conference (Brisbane, Queensland, 1935), and no new appointment was made to replace him.

The chairman was empowered to co-opt further members. In order to make the Committee t ru ly international in scope, the co-operation of prominent sugar technologists in all the important sugar cane countries was solicited, those connected w i th official institutions or technical organizations being chosen wher­ever possible. The response was most gratifying, and the following men have served on the Committee at various times, many of them throughout the entire period during which it has been functioning:

Argentine: W. E. Cross; Australia: Norman Bennett, W. R. Harman, A. Jarratt, G. S. Moore; British and French West Indies: Walter Scott, J. G. Davies; Cuba: A.J . Keller, W. B. Saladin, H. D. Lanier, A. P. Fowler jose Santos; Hawaii: W. R. McAllep, W. L. McCleery, S. S. Peck; India: Noel Deerr, J. H. Haldane, K. C. Banerji; Japan: Migaku Ishida, S. Kusakado; Java: P. Honig, C. Sijlmans, Ph. van Harreveld; Louisiana: C. E. Coates, A. G. Keller; Mauritius: Louis Baissac; Mexico: T. H. Murphy; Natal : H. H. Dodds, G. C. Dymond; Peru: Gerardo Klinge; Philippines: Herbert Walker, E. T. Westly; Puerto Rico: M. A. del Valle, Jaime Annexy, E. M. Copp; Santo Domingo: Rafael Cuevas Sanchez.

In some of these countries sub-committees were formed to advise the members of the Committee.

To all these men the chairman again expresses his sincere gratitude because wi thout their wi l l ing, sympathetic, and efficient help it would have been impossible to accomplish the large and difficult task allotted to the Committee.

Since the members of the Committee are scattered all over the wor ld it was necessary to undertake the work largely by means of questionnaires and correspondence. The replies to the various questionnaires were analysed, arranged, and summarized by the chairman, who then prepared comprehensive reports for each of the meetings of the Society. These reports were discussed at the Conferences by the Committee members present or their proxies, and all amendments agreed upon were entered in the reports. The revised reports were submitted to the Society as a whole, were adopted by it, and published in the Proceedings. The general terms and definitions, and the system of milling control were thus disposed of at the Third Conference in 1929. The control of the boiling house, and the methods of weighing, measuring, sampling, and analysis were reported at the Fourth Conference in 1932, but since the Committee was poorly represented at that meeting it was decided to resubmit the report to all the members of the Committee by correspondence. The final report was presented at the Fifth Conference in 1935, and was adopted. But the Committee was retained in office in order to keep the methods up to date and to revise them from time to t ime, in keeping wi th progress in sugar technology. Accordingly, a report was presented at the Sixth Conference in 1938, but only few changes in the methods were made at that t ime.

In the present book the reports of the Committee have been rearranged and systematized so that they may be more readily consulted. In some instances the original text has been somewhat condensed, in others amplified, [always keeping in mind the intent of the Committee's work . The purpose of this treatise is not to serve as a complete manual of control methods, but rather to explain the principles which guided the Committee in arriving at its decisions, and to emphasize essential points. Those well known methods the details of which may be readily found in any of the generally used handbooks of factory control are not described at length, but simply referred to by name. But the methods recommended by the Committee which are not so widely known, are given in full in Chapter VII. In other words, the book is not meant to replace existing manuals, but to supplement them and to be used as a guide for those countries or associations that desire to bring their control methods in line wi th those recommended by the Committee, and thus to accomplish the purpose for which the latter was created. It is hoped that the publication of this international system of factory control may be found helpful toward that end.

The Committee accepted for its guidance the following principles enunciated by S. S. Peck: "Your committee should strive for three main objectives, namely, accuracy, clarity, and simplicity; and of these three I consider the last as important as the first two . In striving for greater accuracy, formulas have become so complex that they are practically useless. If the committee stress simplicity of statement which wi l l not conflict w i th accuracy and clarity, they may be able to do some persuading to an agreement on terms." It was also postulated that wherever direct determinations can be accurately and simply made, they should be preferred to indirect determinations or calculations, and further, that practical considerations should be favoured against theoretical speculations.

CONTENTS PAGE

CHAPTER I

GENERAL DEFINITIONS . . . . . . . . . . . . . . 9

CHAPTER II

PRINCIPLES OF THE MILLING CONTROL . . . . . . . . . . . . . . 17

CHAPTER III

DETERMINATIONS AND CALCULATIONS FOR THE MILLING CONTROL . . 24

CHAPTER IV

CONTROL OF THE BOILING HOUSE . . . . . . . . . . . . . . 28

CHAPTER V

METHODS OF WEIGHING AND MEASURING . . . . . . . . . . . . . . 41

CHAPTER VI

METHODS OF SAMPLING . . . . . . . . . . . . . . 48

CHAPTER VII

METHODS OF ANALYSIS . . . . . . . . . . . . . . 56

CHAPTER VIII

RECAPITULATION OF FACTORY DATA . . . . . . . . . . . . . . 78

APPENDIX I

CONVERSION OF UNITS . . . . . . . . . . . . . . 83

APPENDIX II

NOTES ON STANDARD TABLES . . . . . . . . . . . . . . 88

EDITOR'S NOTE

It is ironical that, in the wr i t ing of a book of standard methods, one cannot have recourse to a standard English language. The original edition of this book, set up and printed in U.S.A., naturally employed American forms of spelling exemplified in such words as fiber and sirup. Convenience dictated that, in the present edition, the forms used in Australia should be adopted. A glossary of equivalent terms was considered hardly necessary!

Furthermore, wi th apologies to the international metric standards, the comma (,) has been used for subdivisions wi th in whole numbers or decimals and the point (•) for the decimal point; metric abbreviations have been terminated wi th a period (kg. l i t .), the abbreviation sq. has been used instead of the index 2, and the abbreviation cu. instead of the index 3.

CHAPTER I

General Definitions

Explanatory notes which do not form part of the official definitions are printed in small type.

1. Cane. Dutch: Riet; French: Canne; Spanish: Cana. The raw material delivered at the factory, including clean cane, field trash, water, etc. The word "soil", found in some of the definitions of cane, has been left out because it is included in the definition of "field trash" (No. 2). In some countries where the cane received at the factory is cleaned prior to milling the material defined as "Cane" above is known as "Gross Cane", which, after cleaning becomes "Net Cane" or "Clean Cane". These terms have not yet received International recognition.

2. Field Trash. D.: Met riet ingevoerd vuil; F . : Paille; Sp.: Paja. The leaves, tops, dead stalks, roots, soil, etc., delivered at the factory with the clean cane.

3. Fibre. D.: Vezelstof, or Vezel; F . : Ligneux; Sp.: Fibra. The dry, water-insoluble matter in the cane.

4. Normal Weight. D.: Normaal gewicht; F . : Poids normal; Sp.: Peso normal. The weight of sample equal to that weight of pure cane sugar which, when dissolved in water to a total volume of 100 ml. at 20° C, gives a solution reading 100 degrees of scale when examined in a saccharimeter, in a tube 200 mm. long, at 20° C. The fixing of the hundred degree point of saccharimeters is to be left to the International Commission for Uniform Methods of Sugar Analysis.

5. Pol. D.: Pol; F.: Pol; Sp.: Pol. The value determined by direct or single polarization of the normal weight solution in a saccharimeter. The term is used in calculations as if it were a real substance. Various terms were proposed for this concept before and at the com­mittee meetings, but all had to be rejected for one reason or another. "Polarization" was considered too long, and finally "Pol" was unani­mously agreed upon. It is already in use in several countries.

6. Sucrose. D.: Saccharose; F. : Saccharose; Sp.: Sacarosa. *The pure chemical compound of that name, also known as Saccharose or cane sugar.

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The method of determination has advisedly been left out of the definition, since the concept of a definite quantity of sucrose existing in an impure material is quite acceptable. Any departures from scientific truth in the reporting of sucrose quantities are regarded as limitations of analytical method or justifiable approximations.

*Indicates new or amended definition, subject to confirmation.

7. Brix. D.: Brix; F . : Brix; Sp.: Brix.

*The Brix of a solution is the concentration of a solution of pure sucrose in water (expressed as parts by weight of sucrose per 100 parts by weight of solution) having the same density as the solution at the same temperature. This definition is general in form. The Brix of a solution of pure sucrose in water is a direct measure of the percentage of sucrose or solid matter by weight in the solution. For an impure solution the Brix represents the apparent percentage of solid matter as determined by a densimetric method. The Brix is then numerically the same as the percentage of solid matter in a pure sucrose solution of the same density. In the practical determination of Brix it is assumed that the test solution has the same temperature coefficient of density as the corresponding sucrose solution. If refractive index be adopted instead of density as a basis of comparison the value derived is known as Refractometer Brix. (Definition 9).

8. Gravity Solids. D.: Schijnbare droge stof; F . : Matieres seches apparentes; Sp.: Brix.*

The weight of solids calculated from the Brix determination. *In the Spanish idiom, as frequently in English also, Brix is regarded as a substance identical with gravity solids.

9. Refractometer Brix. D.: Refractometrische Brix; F . : Brix refractometrique; Sp.: Brix refractometrico.

The per cent, by weight of solids in solution as indicated by the sugar refractometer, or as derived from the refractive index and reference to tables of equivalent per cent. sucrose and refractive indices. The refractometer may be used not only for the determination of the per cent. solids, in the laboratory or in the vacuum pan, but also for that of fine grain in molasses. The conversion of refractive indices into per cent. solids is to be effected by means of the International Scale (1936) of the International Commission for Uniform Methods of Sugar Analysis. If a sugar refractometer is used it should be calibrated according to the International Scale.

10. Dry Substance. D.: Ware droge stof; F . : Matieres seches reeles; Sp.: Materia seca.

*The material remaining after drying the product examined. As in the case of Sucrose (Def. 6) the concept of dry substance is clear, and limitations in our ability to measure dry substance do not affect the significance of the term. In practice the drying is achieved almost invariably by evaporation of the volatile component at elevated temperature until the rate of loss of weight becomes insignificant.

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11. Suspended Solids in Mixed Juice. D.: Vuil in ruwsap; F.: Matieres en suspension dans le jus melange', Sp.: Solidos en suspension en el jugo mezclado. The solids in mixed juice removable by decantation. It was considered advisable to add the phrase "In mixed juice" to the term itself because suspended solids occur also in other products, like molasses, but are then of an entirely different nature. It was also decided not to use the words "in solution" or "insoluble" in the definition because they give no exact idea about the state of dispersion of the particles.

12. True Purity, abbreviated T. Purity. D.: Ware reinheid; F. : Purete reelle; Sp.: Pureza real. The percentage proportion of sucrose in the dry substance.

13. Gravity Purity, abbreviated G. Purity. D.: Saccharose­reinheid, or Saccharose/Brix; F . : Purete Clerget; Sp.: Pureza Sacarosa/Brix. The percentage proportion of sucrose in the Brix or gravity solids.

14. Purity. D.: (Schijnbare) Reinheid; F. : Purete (Apparente); Sp.: Pureza (aparente). The percentage proportion of pol in the Brix or gravity solids.

15. Reducing Sugars, or R.S. D.: Reduceerende suiker, or R.S.; F. : Reducteurs; Sp.: Azucares reductores. The reducing substances in cane and its products, determined as described in Chapter VII, and calculated as invert sugar. The components of invert sugar are termed "dextrose" and "levulose". The term "glucose", to designate either invert sugar or dextrose, is to be avoided as it may lead to misunderstandings.

16. Ash. D.: Asch; F. : Cendres; Sp.: Cenizas. The residue remaining after burning off all organic matter. For details, Chapter VII should be consulted.

17. Non-pol. D.: Nietsuiker; F . : Non-Sucre; Sp.: No-pol. *Brix minus pol.

18. Non-sucrose. D.: Nietsaccharose. F . : Non-Saccharose; Sp.: No-sacarosa. *Dry substance minus sucrose.

19. R.S.—Ratio. D.: Reduceerende suiker-pol quotient; F . : Quotient reducteurs-pol; Sp.: Coeficiente azucares reductores-pol (Coeficiente AR—P). The percentage ratio between reducing sugars and pol.

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20. R.S.—Sucrose Ratio. D.: Reduceerende suik&r-saccharose quotient; F . : Quotient reducteurs-saccharose; Sp.: Coeficiente azucares reductores-sacarosa (Coeficiente AR—S). The percentage ratio between reducing sugars and sucrose.

21. Pol-Ash Ratio. D.: Asch quotient; F . : Quotient satin; Sp.: Coeficiente salino (Coeficiente P—C). The ratio between pol and ash.

22. Sucrose-Ash Ratio. D.: Saccharose-asch quotient; F . : Quotient saccharose-cendres; Sp.: Coeficiente sacarosa-cenizas {Coeficiente S—C). The ratio between sucrose and ash.

23. R.S.-Ash Ratio. D. : Reduceerende suiker-asch quotient; F . : Rapport reducteurs sur cendres; Sp.: Coeficiente azucares reductores-cenizas (Coeficiente AR—C). The percentage ratio between reducing sugars and ash.

24. Absolute Juice. D.: Gemiddeld sap; F. : Jus absolu; Sp.: Jugo absoluto.† All the dissolved solids in the cane plus the total water of the cane; cane minus fibre. †Guarapo, synonymous with Jugo, is generally used in Cuba and Puerto Rico. It was decided to abandon entirely the term "normal" juice, because it has several different meanings at the present time, and its retention would only add to the existing confusion.

25. Undiluted Juice. D.: Onverdund sap; F . : Jus non-dilue; Sp.: Jugo sin diluir. The juice expressed by the mills or retained in the bagasse, corrected for imbibition water. For purposes of calculation it has the Brix of the primary juice (No. 28). The Committee decided to report, for the purpose of comparing milling results, besides the Milling Loss also the Java figure "Undiluted juice in bagasse, per cent. fibre". This will make it possible after some time to decide which of the two figures is better for international com­parisons. It was therefore necessary to define "undiluted juice".

26. Undetermined Water. D.: Restwater; F. : Eau non deter­minee; Sp.: Agua no determinada. Cane minus fibre minus total undiluted juice in cane. In its calculation the suspended solids in mixed juice are also con­sidered. See under No. 25.

27. First Expressed Juice. D.: Eerst uitgeperst sap; F . : Jus de premiere pression; S.: Primer jugo extraido.

The juice expressed by the first two rollers of the tandem.

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28. Primary Juice. D.: Voorperssap; F. : Jus primaire; Sp.: Jugo primario. All the juice expressed before dilution begins.

29. Secondary Juice. D.: Naperssap; F . : Jus secondaire; Sp.: Jugo secundario. The diluted juice which, together with the primary juice, forms the mixed juice (No. 32).

30. Last Mill Juice. D.: Laatste molensap; F.: Jus du dernier moulin; Sp.: Jugo del ultimo molino. The juice expressed by the last mill of the tandem.

31. Last Expressed Juice. D.: Laatst uitgeperst molensap', F. : Dernier jus exprime; Sp.: Jugo final. The juice expressed by the last two rollers of the tandem.

32. Mixed Juice. D.: Bruto ruwsap; F . : Jus melange; Sp.: Jugo mezclado. The juice sent from the crushing plant to the boiling house.

33. Bagasse. D.: Ampas; F. : Bagasse; Sp.: Bagazo. The residue obtained from crushing cane in one or more mills. Known respectively as First mill bagasse, or Final mill bagasse, etc.; and as Last mill bagasse, or Final bagasse, or simply bagasse, when the material from the last mill is referred to.

34. Residual Juice. D. : Sap in ampas; F. : Jus residuel; Sp. Jugo residual. The juice left in the bagasse; bagasse minus fibre.

35. Subsider Juice. Characterized as first or second when double settling is practised. D.: Dunsap bezinking, or Schoonsap (lste or 2de); F.: Jus defeque (ler or 2nd); Sp.: Jugo decantado (1st), and Jugo de las cachaceras (2nd). The juice decanted from the mud or settlings in the course of the clarification process. If double decantation is practised, the juices obtained in the two operations are further character­ized as shown above.

36. Filtered Juice. D.: Filtersap; F . : Jus des filtres; Sp.: Jugo de los filtros. The combined nitrates from the filters. If double filtration of muds is practised the resulting juices are further characterized as first, or second, respectively. With the introduction of filters other than presses (Oliver, etc.) it became necessary to omit the word "press" in this term.

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37. Filter Washings. D.: Afzoetsap; F. : Lavage; Sp.: Lavados de los filtros. The runnings obtained from the filters during the process of washing or sweetening off.

38. Clarified Juice. D.: Dunsap (naar verdamping); F . : jus clair; Sp.: Jugo clarificado. *The main product passed out of the section of the factory devoted to clarification of the juice. The clarified juice normally goes on into the evaporators, and constitutes the whole, or the major portion of the "Evaporator Supply Juice".

39. Carbonatation Juice. D.: Carbonatatiesap; F . : Jus carbonate; Sp.: Jugo carbonatado. The juice coming out of the carbonatation tanks after filtering, but without washing. It is termed "first" or "second", according to the stage of carbonatation.

40. Filter Cake. D.: Filtervuil; F . : Tourteaux des filtres; Sp.: Cachaza, or Tortas de los filtros. The residue removed from process by filtration.

41. Syrup. D.: Verdampingsdiksap; F . : Clairce, or Strop; Sp.: Meladura. The concentrated juice from the evaporators.

42. Massecuite. D.: Kooksel; F.: Massecuite; Sp.: Masa cocida. The mixture of crystals and mother liquor discharged from the vacuum pan. Massecuites are classified, according to descend­ing purity, as first, second, etc., or A, B, etc.

43. Magma. D.: Aangepapte suiker; F.: Magma; Sp.: Magma. A mixture of crystals and sugar liquor produced by mechanical means.

44. Molasses. (First, second, etc., to final molasses). D.: Afloop (first to penultimate molasses), Melasse (final molasses); F.: Egout (pauvre) (first to penultimate molasses), Melasse (final molasses); Sp.: Miel; final molasses is termed Melaza, or Miel final. The mother liquor separated from the crystals by mechanical means. It is termed "first", "second", etc., or "A", " B " , etc., according to the massecuite from which it is obtained.

45. Wash. D.: Klaarsel, or dekstroop, or klare; F . : Egout riche; Sp.: Lavados de las centrifugas. The diluted molasses thrown off the centrifugals during wash­ing, and collected separately.

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46. Jelly. D.: Draadkooksel; F . : Cuite au filet; Sp.: Filete. A boiling which has been concentrated without graining to such a consistency ("stringproof") that it may be expected to crystallize spontaneously upon standing.

47. Sugars. D.: Suikers; F. : Sucres; Sp.: Azucares. The crystals (including any adherent molasses) recovered from the massecuite, usually in centrifugals. According to local conditions, different types of sugar are produced, to be either shipped or returned to process. No attempt has been made to define each of the many types of sugars produced, because this is largely a commercial rather than a technical question.

48. Seed. D.: Intrekmassa; F. : Pied de cuite; Sp.: Pie. Dry sugar or magma used as a footing for boiling a massecuite.

49. Shock Seed. D. : Entgrein; F.: Amorce de crystallisation; Sp.: Semilla. Sugar powder taken into the vacuum pan to induce crystalliza­tion in a strike being boiled.

50. Imbibition. D.: Imbibitie; F . : Imbibition; Sp.: Imbibicion. The process in which water or juice is put on the bagasse to mix with and dilute the juice present in the latter. The water so used is termed imbibition water.

51. Maceration. D.: Maceratie; F. : Maceration; Sp.: Maceracion. The process in which the bagasse is steeped in an excess of water or juice, generally at a high temperature. The water so used is termed maceration water. According to definitions 50 and 5.1, maceration is a special case of imbibition.

52. Dilution Water. D.: Imbibitiewater in ruwsap; F . : Eau de dilution; Sp.: Agua de dilucion. The portion of imbibition or maceration water present in the mixed juice. If the term "Dilution" is used, it should always be further characterized by giving the basis to which it refers. See Chapter III .

53. Juice Extraction. D.: Sappersing; F . : Pression; Sp.: Extraccion de jugo, or Jugo extraido. The percentage weight of juice extracted by the mills. In each case it should be definitely stated what kind of juice is referred to, and to which basis the percentage relates.

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54. Pol Extraction. D.: Suikerwinningsquotient; F. : Extraction aux moulins; Sp.: Extraction de pol. Pol in mixed juice per cen. pol in cane. A closely related term is Brix Extraction of which the definition is analogous.

55. Sucrose Extraction. D.: Saccharosewinningsquotient; F. Extraction de saccharose; Sp.: Extraction de sacarosa. Sucrose in mixed juice per cent. sucrose in cane.

56. Java Ratio. D.: Factor f (not in use any more); F . : Coefficient de jus; Sp.: Coefitiente Java. Pol (or sucrose) per cent. cane, divided by pol (or sucrose) per cent. first expressed juice, and the result multiplied by 100. The Committee decided to define this figure without recommending it for international adoption, because it is only of local importance. In some places pol figures are used, in others sucrose figures. In Java the ratio was based on pol of primary juice instead of in first expressed juice. The "Natal" ratio, used only in that country, has been omitted.

57. Extraction Ratio. D.: Extractieverhouding; F . : Coefficient d'extraction; Sp.: Coefitiente de extraction. The percentage ratio of unextracted sucrose (pol) to fibre in cane. See also Chapter II.

58. Milling Loss. D.: Verloren suiker per cent. vezel; F . : Coefficient saccharose-ligneux; Sp.: Perdida de molienda. The percentage ratio of sucrose (pol) in bagasse to fibre in bagasse. See also Chapter II.

59. Deterioration (Safety) Factor. D.: Veiligheidsfactor; F . : Coefficient de deterioration; Sp.: Factor de deterioro. A ratio indicating the probable keeping quality of a raw sugar, calculated by dividing the per cent. moisture in the sugar by (100—per cent. sucrose or pol in the sugar). A factor exceeding 0.25 is considered dangerous. In Australia the Deterioration Factor (F) has been replaced by the "Dilution Indicator", which equals 100F/ (1 —F).

60. Revised Elliott Filtration Rate. D.: FiUratiesnelheid volgens Elliott (herzien); F . : Taux de filtration selon Elliott (revise); Sp,: Filtrabilidad segun Elliott (revisada). An arbitrary figure introduced by Elliott, to indicate the relative speed of filtration of a sugar solution through a filter aid.

61. Revised Retardation Factor. D.: Vertragingsfactor (herzien); F . : Coefficient de retardement (revise); Sp.: Factor de retardation (revisado). The ratio between (135 — Revised Elliott Filtration Rate) and (100 — sucrose or pol of the sugar).

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CHAPTER II

Principles of the Milling Control

The recommendations of the Committee for the control of the milling plant are based on the following considerations:

Fundamental Equation. The fundamental equation for the weights of the products

entering and leaving the mill states that cane plus water equals mixed juice plus bagasse. In the ideal system of control all these four weights would be determined directly. An error in any one of the four weights would throw the equation out of balance, and the cause of the error could then be traced. Practical considera­tions have so far ruled out this ideal system.

The Committee has agreed that the weight of the cane and that of the mixed juice should be determined in all cases where the mixed juice as such is clarified. Calculation of the juice weight from its volume is not advisable, but is permissible where juice scales have not yet been installed. The Committee recognizes the fact that in a few exceptional cases the weight of the cane cannot be easily determined by direct weighing. In all these cases the factories are urged to state in their reports how the weight of the cane has been calculated.

The weights of cane and of mixed juice having been determined there are still two unknown quantities left. If we apply the principle of direct determination, postulated by the Committee, one of the two unknowns, that is either the weight of the added water, or that of the bagasse, must be measured in order to calculate the other by means of the fundamental equation. The Committee has come to the conclusion that the only correct solution of the problem is the weighing of the bagasse, because there are serious objections to all other methods. Unfortunately, no practical weighing machine adapted to large scale operation has so far been placed on the market- Until the weighing of bagasse becomes an actuality it will be necessary to find its weight by some other means. Among the methods that have been used or proposed for this purpose, the following may be mentioned:

1. The weight of the imbibition or maceration water is deter­mined as such or is derived from its volume, and the weight of the bagasse is found by applying the fundamental formula given above. This sytem is used in a number of countries.

2. The fibre per cent. cane is directly determined on samples of the cane, and the bagasse per cent. cane calculated from fibre

17

per cent. cane and fibre per cent. bagasse. The weight of the imbibition or maceration water is then calculated by the funda­mental formula. This method is also used in several countries.

3. The fibre per cent. first mill bagasse is found from the analysis of this bagasse (moisture and Brix, both determined directly); the weight of the primary juice is calculated from the Brix of mixed, primary, and secondary juices; finally the fibre per cent. cane is calculated from the fibre per cent. first mill bagasse, weight of primary juice, and weight of cane. Then the weight of the bagasse is found as shown under 2 above.

4. The fibre per cent. cane is found from the weight of the mixed juice, using Deerr's formula (Cane Sugar, p. 553) and a "Milling factor" (ratio between Brix of absolute juice and of first expressed juice) of 0.975. Then the weight of the bagasse is found as under 2 above.

5. The weight of the imbibition water is calculated by assuming that the imbibition water per cent. cane is equal to the dilution per cent. normal juice.

6. The bagasse per cent. cane is arbitrarily considered to equal 103 minus normal juice extracted per cent. cane.

7. The bagasse per cent. cane is calculated from undiluted bagasse per cent. cane, and undiluted bagasse per cent. bagasse, assuming 20 per cent. adsorption water in the fibre.

If we now apply the criteria of accuracy, clarity, simplicity, and freedom from assumptions, to the above methods of deter­mining the weight of the bagasse, methods 5 and 6 may be ruled out at once, as purely arbitrary. Similarly, method 7, assuming 20 per cent. adsorption water in the fibre, may or may not be correct in individual cases.

Method 4 assumes a milling factor of 0.975. The question of this factor will be discussed below, and it will be shown that it is neither necessary nor advisable to depend on a milling factor at all, except where the weights of cane or mixed juice, or of both, are unknown.

Method 3, where fibre per cent. first mill bagasse and weight of primary juice are determined, has the advantage over the direct determination of fibre per cent. cane that it assures a better and more reliable sample of material for fibre determination. But when different varieties of cane are ground together, much of this advantage is lost. Furthermore, since the weight of primary juice must also be either directly determined or calculated, the method is really too cumbersome to fulfill the requirements of simplicity which is one of the principal aims of the control methods for international use.

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This leaves then either the direct determination of the weight of the imbibition water (Method 1), or the direct determination of fibre per cent. cane (Method 2). Both of these methods are also open to serious objections. The first assumes that all the water that is weighed or measured is actually retained by the juice and the bagasse. But there is undoubtedly loss by evaporation, especially when hot water is used. If the bagasse is actually steeped in hot water, as is done in some places, the loss by evapora­tion must be considerable. On the other hand, water which has not been weighed or measured often finds its way into the mill, accidentally or otherwise. It is maintained by some that the loss by evaporation is more or less counter-balanced by the gain from water in excess of that actually measured, but such an assumption does not conform to the requirement of accuracy.

The direct determination of fibre per cent. cane (Method 2) is objected to on account of the difficulty of sampling. It stands to reason, and it has been shown by actual experiment, that a few stalks of cane, taken at random, are rarely representative of an entire load of cane. If only one variety is ground the errors may, during the course of a season, be mutually compensating, but this can hardly be depended upon when a number of varieties are ground.

The Committee has decided that, until it becomes possible to weigh the bagasse directly, it will be necessary to use either Method 1 or Method 2, with the clear understanding that neither one of them is free from objections.

Juice Figures. Originally the juice supposed to exist in the cane was called

"Normal Juice". But in some countries the normal juice is taken to be the juice extracted by dry milling, leaving out of consideration the juice left in the bagasse, while in others it includes the residual juice. This in itself has led to a great deal of confusion. But the principal difficulty in defining normal juice has perhaps been the fact, generally acknowledged, that the cane contains not only juice proper (which in the living cane is not homogeneous), but also water loosely held by the fibre. A part of this water is mixed with the juice itself during the milling process, the more the heavier the pressure. Java adheres, in theory at least, to the concept of dry milled cane as a mixture of undiluted juice, fibre, and "undeter­mined" water. In calculating the undetermined water in the course of the milling control, the Brix of the undiluted juice in both mixed juice and bagasse is taken to be equal to that of the primary juice, in other words, the so-called "Milling factor" equals 1, which is a purely arbitrary figure. When the sum of the undiluted juices in mixed juice and bagasse is added to the dry fibre, and the total deducted from the cane, there is found a rest which is charged to undetermined water. The quantity of this undetermined water

19

would naturally be different if the brixes of the undiluted juice and of the primary juice were not taken to be equal, and with a proper selection of the milling factor the undetermined water could be made to disappear entirely.

The Committee has decided that it is best to ignore the undeter­mined water entirely for purposes of the milling control, and to consider the juice in the cane, under dry milling conditions, to be known under the name of ''Absolute Juice", as the difference between weight of cane and weight of dry fibre, for the following reasons:

1. This concept answers the requirements of simplicity and clarity.

2. It does away with any assumptions regarding the undeter­mined water and its behaviour during the milling process.

3., and most important, it makes it possible to use a simple system of milling control in which it is necessary to know only the weights of cane, of mixed juice, and of bagasse (determined as shown above), and the composition of the mixed juice and of the bagasse.

This system dispenses entirely with the milling factor which has been the bugbear of the cane sugar industry for many years. It is probable that no uniformity could ever be reached if this factor were retained in the milling control. It must be frankly admitted that the character of the first expressed juice or the primary juice is bound to vary from factory to factory with the nature of the varieties ground. In the second place, either a fixed factor would have to be adopted, such as 1 or 0.975, etc., any of which cannot be right in all cases at the same time, or else the milling factor must be determined frequently by dry crushing or by crushing with juice imbibition, neither one of which is a simple operation by any means. Nor does it guarantee accuracy, because such determinations can be made only periodically since they interfere with regular operation. As Peck has aptly put it, the numberless calculations of complex nature derivable from the milling factor and from the composition of the "normal juice" make confusion worse confounded; one can get any results one wants, by slight changes in the factor.

With the definition of absolute juice recommended by the Committee, the determination of the few data previously mentioned makes it possible readily to calculate by well known formulas (see Chapter III) all the juice extraction and dilution figures, and the weight and composition of the juice left in the bagasse.

Composition of the Bagasse. This subject needs to be considered in a little more detail.

The requirements of accuracy and simplicity demand that the composition of the bagasse should preferably be determined by

20

direct analysis. The usual custom heretofore has been to determine only dry substance and polarization, but to calculate Brix and fibre. The fibre is dry substance minus Brix. The Brix has generally been derived from the polarization of the bagasse and the purity of the last expressed or last mill juice. The investiga­tions of Khainovsky1 and of Egeter2 have definitely shown that the purity of the juice in the bagasse is lower than that of the last mill juice, and that the purity of the juice left in the unbroken cells is extremely low. The expression of the bagasse juice itself does not help matters either, because even then the unbroken cells are not all ruptured. Egeter has devised a method for the direct determination of Brix in bagasse by water extraction and measure­ment of the specific gravity of the extract, but because of the great dilution this determination requires extreme care and is not suitable for routine control. Until a more practical method can be found it will be necessary to calculate the Brix as outlined above.

Figures Used for Judging Milling Results. The Committee has recommended that the following figures be

reported for this purpose: Extraction, Milling Loss, Extraction Ratio, Absolute Juice in Bagasse per cent. Fibre, Reduced Extrac­tion, and Undiluted Juice in Bagasse per cent. Fibre.3 It may be advisable later to reduce the number of these criteria, according to the experience gained in their international use. It is generally admitted that the milling results cannot be expressed adequately by a single figure, and that at best several must be used in con­junction, viewing the results from different angles.

1. Extraction.—This figure is very generally employed to convey some idea of the financial results achieved in milling. It is influenced by the character of the cane, especially by fibre and sucrose in cane. The extraction is to be reported on the basis of sucrose figures, for reasons given in Chapter IV. But as long as there are many factories which do not as yet determine sucrose in the different products it will be necessary for those that do so to report also pol extraction, and other figures derived from it so tha t a universal comparison may be possible on the pol basis.

2. Milling Loss.—This, and the terms listed subsequently, aim to express the milling result in a more technical manner than the extraction does. The milling loss is the simplest of these terms, giving the percentage ratio between sucrose (pol) per cent. bagasse and fibre per cent. bagasse, but it does not take into consideration the sucrose per cent. cane.

3. Extraction Ratio.—This figure, which has been found useful in Hawaii and other countries for purposes of comparison, is the percentage ratio of (100 — sucrose extraction) to fibre per cent. cane. Like the extraction, it is to be reported on both the sucrose and the pol basis.

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4. Reduced Extraction.—This figure, proposed by Deeri*, reduces the extraction to a common standard basis of 12.5 per cent, fibre in cane.

If the juice in bagasse, per cent, fibre, be designated by v, the extraction by e, and the fibre per cent, cane by /, then

The extraction e may be either sucrose (pol) or Brix extraction. As Deerr has pointed out, the factory executive is interested more in sugar losses than in Brix losses. On the other hand, the Brix is known to fluctuate less during the milling operation than the sucrose. In the particular case of the Reduced Extraction the Committee has decided to follow Deerr's suggestion and to use the sucrose (pol) extraction for e. Solving the above formula for e, we obtain:

The value of v, for e and / actually found, is calculated from the control by the formula for v given above. Then the reduced extraction, designated by equals

5. Absolute Juice in Bagasse, per cent. Fibre. In calculating this figure, the Committee has decided to use Brix rather than sucrose (pol) as the basis. The formula used is analogous to that given above for v, but the Brix extraction b is substituted for the sucrose extraction e. Then absolute juice in bagasse per cent, fibre

or the following equivalent formula may be used:

6. Undiluted Juice in Bagasse, per cent. Fibre. Although the Committee has established the general rule that no milling factor is to be used in the control of the milling plant, it deferred to the wishes of the Java technologists by deciding that, for the present at least, the undiluted juice in bagasse, per cent, fibre, is to be reported alongside with the other five criteria already mentioned. The calculation is made by a formula analogous to the second one given under 5, the Brix of the absolute juice being replaced by the Brix of the primary juice:

22

This makes it necessary to determine the Brix of the primary juice, besides that of the mixed juice. As has been stated pre­viously, it is hoped later on to eliminate some of these six criteria, and to retain only those that have proved their utility in practice.

Milling Efficiency Figures. It must be clearly understood that the six criteria given above

express merely the milling result, and are affected by the milling equipment as well as by the operation of the milling plant. Various systems have been proposed by which the milling results actually obtained may be compared with an arbitrary "normal" or "ideal" standard. But none of these systems has been widely studied in its practical application, and the Committee has decided not to recom-mend any of them for the present.

Mechanical Milling Equipment and its Performance. The Committee urges the publication, by factories in all coun-

tries, of data regarding the milling equipment used, such as types and sizes of knives, shredders, crushers, number and dimensions of rollers, grooves, mill openings, speeds of rollers, pressure on rollers, and similar information. But it was decided not to adopt as yet any of the mechanical milling performance figures, like grinding coefficient, tonnage ratio, tonnage fibre ratio, etc., because none of these appears to be entirely satisfactory for international comparisons.

Field Distribution and Payment for Cane. The Committee has reached the conclusion that payment for

cane, although closely connected with factory control, is primarily of local importance and should be regulated according to local conditions. This subject is therefore not considered to be amenable to international agreement, and all data such as "Quality Ratio", "Cane Ratio", "Sugar Ratio", etc., are to be omitted.

si

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CHAPTER III

Determinations and Calculations for the Milling Control

The milling control data to be determined directly, and those derived by calculation, in accordance with the principles outlined in the foregoing Chapter, are shown below in systematic order.

As stated previously, the Committee has sanctioned two different methods for arriving at the weight of the bagasse. For this reason items 12 to 16 of the list appear in duplicate, under Scheme A and Scheme B. All the other data are obtained in the same way in either modification. The factory reports should always state which of the two schemes has been used. If for any reason neither of them has been adhered to, the reports should clearly state in what respect the control methods employed have differed from those recommended by the Committee.

Obviously, the sequence of the arithmetical operations may be altered or equivalent formulas may be used, without deviating from the established principles of the control system. Calculated data, other than those listed, may be readily obtained by formulas analogous to those given.

Data to be directly determined in all cases:

1. Weight of cane. 2. Weight of mixed juice (Calculation from volume permitted,

but not recommended). 3. Brix per cent. mixed juice. 4. Sucrose (pol) per cent. mixed juice. 5. Dry substance per cent. bagasse. 6. Pol per cent. bagasse, = Sucrose per cent. bagasse. 7. Brix per cent. last expressed juice. 8. Pol per cent. last expressed juice. 9. Brix per cent. primary juice (to be used only for calculating

undiluted juice in bagasse, per cent. fibre; see p. 22).

Brix and Fibre, per cent. Bagasse:

10. Brix per cent. bagasse = Pol per cent. bagasse (6), times Brix per cent. last expressed juice (7), divided by pol per cent. last expressed juice (8).

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11. Fibre per cent. bagasse = Dry substance per cent. bagasse (5) minus Brix per cent.bagasse (10).

Weight of Bagasse, etc. : Scheme A, Scheme B,

based on weight of imbibition based on fibre per cent. cane. water.

12. Weight of imbibition water, 15. Fibre per cent. cane, deter-determined directly. mined directly.

13. 14.

14. Bagasse per cent. cane = 14. Weight of bagasse = 100 times weight of bagasse Bagasse per cent. cane (14 B) (13 A), divided by weight times weight of cane (1), of cane (1). divided by 100.

15. 12.

16. Weight of fibre = 16. Weight of fibre = Fibre per cent. bagasse (11) Fibre per cent. cane (15 B) times weight of bagasse times weight of cane (1), (13 A), divided by 100. divided by 100.

Juice Figures:

17. Mixed juice per cent. cane = 100 times weight of mixed juice (2) divided by weight of cane (1).

18. Purity of mixed juice = 100 times sucrose (pol) per cent. mixed juice (4) divided by Brix per cent. mixed juice (3).

19. Weight of Brix in mixed juice = Brix per cent. mixed juice (3) times weight of mixed juice (2), divided by 100.

20. Weight of sucrose (pol) in mixed juice = Sucrose (pol) per cent. mixed juice (4) times weight of mixed juice (2), divided by 100.

21. Weight of Brix in bagasse = Brix per cent. bagasse (10) times weight of bagasse (13), divided by 100.

22. Weight of sucrose (pol) in bagasse = Pol per cent. bagasse (6) times weight of bagasse (13), divided by 100.

23. Weight of absolute juice = Weight of cane (1) minus weight of fibre (16).

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24. Brix per cent. absolute juice = [Weight of Brix in mixed juice (19) plus weight of Brix in bagasse (21)], divided by weight of absolute juice (23), and result multiplied by 100.

25. Sucrose (pol) per cent. absolute juice = [Weight of sucrose (pol) in mixed juice (20) plus weight of sucrose (pol) in bagasse (22)1, divided by weight of absolute juice (23), and result multiplied by 100.

26. Purity of absolute juice — 100 times sucrose (pol) per cent. absolute juice (25), divided by Brix per cent, absolute juice (24).

27. Weight of absolute juice extracted = 100 times weight of Brix in mixed juice (19), divided by Brix per cent. absolute juice (24).

28. Absolute juice extracted per cent. cane = 100 times weight of absolute juice extracted (27), divided by weight of cane (1).

29. Weight of absolute juice in bagasse = 100 times weight of Brix in bagasse (21), divided by Brix per cent. absolute juice (24); or weight of absolute juice (23) minus weight of absolute juice extracted (27).

Imbibition and Dilution Figures:

30. Imbibition water per cent. cane = 100 times weight of imbibition water (12), divided by weight of cane (1).

31. Imbibition water per cent. absolute juice = 100 times weight of imbibition water (12), divided by weight of absolute juice (23).

32. Weight of dilution water = Weight of mixed juice (2) minus weight of absolute juice extracted (27).

33. Dilution per cent. cane = Mixed juice per cent. cane (17) minus absolute juice extracted per cent. cane (28).

34. Dilution per cent. absolute juice = 100 times weight of dilution water (32), divided by weight of absolute juice (23).

35. Dilution per cent. absolute juice extracted = 100 times weight of dilution water (32), divided by weight of absolute juice extracted (27).

36. Imbibition water in bagasse per cent. cane = Imbibition water per cent. cane (30) minus dilution per cent. cane (33).

Cane Figures:

37. Weight of sucrose (pol) in cane — Weight of sucrose (pol) in mixed juice (20) plus weight of pol in bagasse (22).

38. Sucrose (pol) per cent. cane = 100 times weight of sucrose (pol) in cane (37), divided by weight of cane (2).

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39. Sucrose (pol) extracted per cent. cane = 100 times weight of sucrose (pol) in mixed juice (20), divided by weight of cane (1).

40. Sucrose (pol) in bagasse per cent. cane = 100 times weight of pol in bagasse (22), divided by weight of cane (1).

Figures used for judging milling results:

41. Sucrose (pol) extraction = 100 times weight of sucrose (pol) in mixed juice (20), divided by weight of sucrose (pol) in cane (37).

42. Milling loss = 100 times pol per cent. bagasse (6), divided by fibre per cent. bagasse (11).

43. Extraction ratio = 100 times [100 minus sucrose (pol) extrac-tion (41)], divided by fibre per cent. cane (15).

44. Reduced extraction; for calculation see p. 22.

45. Absolute juice in bagasse, per cent. fibre; for calculation see p. 22.

46. Undiluted juice in bagasse, per cent. fibre; for calculation see p. 22.

If desired, the percentage composition (sucrose or pol, non-sucrose or non-pol, water) of mixed juice, absolute juice, bagasse, and cane may be calculated with the aid of the data presented.

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CHAPTER IV

Control of the Boiling House

In this division of the factory control there is not quite as much disagreement about fundamentals as in the milling division, and it is considered unnecessary to devote separate chapters to the principles of the boiling house control and their practical applica-tion. All those points about which there is a difference of opinion are discussed in detail under their respective headings, and the reasons for the decisions of the Committee arc fully explained.

Q U A N T I T I E S O F P R O D U C T S .

The operations of the boiling house begin with the mixed juice, except in those cases where milling and clarification form a com-pound system. The mixed juice is to be weighed, as has already been explained. Where this is not possible because of clarification practice the clarified juice is to be weighed.

The Committee has decided that the filter cake, the final molasses, and the sugars are to be weighed also. If there is more than one kind of filter cake, as for instance from juice and syrup filtration, these are to be weighed separately; the same applies to different types of sugar made. If no scales are available, filter cake and molasses have to be measured, but this is not recom-mended because accuracy demands the weighing of these products.

If settlings are returned to the mill they should also be weighed, likewise filter washings returned to the mill, but the latter may be measured and the volume converted to the weight basis. The weights of such settlings and filter washings are needed only to apply corrections to the control data, and they do not appear in the completed reports.

The syrup is weighed in some places, and this practice helps to trace entrainment and inversion losses in a given factory. But there is no need to report syrup weights for international comparisons.

The weights of mixed (clarified) juice, filter cake, sugars, and molasses are to be given as per cent. by weight of cane. The actual weight is to be reported only for the cane ground, in metric tons.

The quantities of the various massecuites are to be measured in the pan and reported, in hectoliters per 10 metric tons (100 quintals) of standard sugar.

The lime used is to be reported in terms of available calcium oxide per thousand parts of cane, that is kilograms per metric ton.

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ANALYTICAL FIGURES. Brix and Pol.—These are to be determined upon mixed juice,

clarified juice, syrup, massecuites, intermediate and final molasses, also on filter washings and on settlings returned to the mill, but in the last two instances the data are used only to apply corrections.

Brix is to be determined on low grade sugars only, but not on high grade, because in the latter case the experimental error may exceed the total moisture content.

A specific gravity determination must be made on muds returned to the mill in order to find the quantity of clear juice contained in them, but again this figure docs not appear in the completed report.

Dry Substance and Pol.—Although control on a dry substance basis would be very desirable, results of dry substance determina-tions on liquid products are time consuming, and in the presence of levulose on the one hand and of insoluble matter on the other they are so uncertain that they offer no real advantages over Brix determinations, in spite of all the recognized shortcomings of the latter. If Brix determinations based on specific gravity are to be replaced by something more useful, the refractometer promises much better chances of success than drying methods.

Dry substance and pol are to be determined on filter cake. Gravity solids in filter cake, if desired for a Brix balance, must be determined separately or calculated.

Dry substance and pol are to be determined and reported on all high grade sugars. In calculations, the dry substance is to be used for Brix or gravity solids.

Sucrose.—As has been previously stated, the entire control should be based on sucrose rather than pol figures. The principal reason for this is that the relative proportions of other optically active components, mainly dextrose and levulose, vary from place to place, and may also change considerably during the manufactur-ing process. This has a profound effect on the ratio of pol to sucrose. Although the sucrose figure is usually higher than the pol, it may be, and often is, lower. The s-j-m formula, and similar formulas, give correct results only if sucrose data are employed.

There is still another important reason why pol figures are unreliable. Polarization results would be comparable only if they were made always and everywhere at the same temperature. Temperature corrections are out of the question because the temperature coefficient of each optically active constituent would have to be considered, and this would necessitate a complete analysis, including a sucrose determination. Furthermore, the direct polarization is greatly affected by the quantity of lead subacetate used for clarifica-tion. Sucrose determinations, on the other hand, are corrected for temperature, and are largely independent of the quanti ty of clarifying agent employed.

29

The Committee has decided that sucrose is to be determined and reported for mixed juice and for final molasses, and also for sugars, except those returned to process or of such high grade that pol and sucrose are the same within the limit of error. In those factories which start the boiling house control with the clarified juice, sucrose must be determined in the latter. For purposes of a sucrose balance, pol in filter cake can safely be used as being equal to sucrose, within the limits of experimental error, but sucrose must be determined in filter washings and muds returned to the mill, to apply necessary corrections. Sucrose need not be deter-mined in the syrup since it has been decided to base recoveries on sucrose in mixed juice, nor in massecuites and intermediate molasses, where pol is sufficient for running control.

Reducing Sugars.—Although reducing sugar determinations present a valuable tool for detecting losses and are therefore encouraged by the Committee, the reporting of such figures for the purpose of international comparisons is not recommended, except in the case of mixed juice and final molasses.

Ash.—What has been said with regard to reducing sugars applies also to ash figures. The Committee recommends that ash be reported upon mixed juice and final molasses. The reporting of both reducing sugars and ash is of importance in view of the work of Thieme, showing that the exhaustibility of molasses is correlated with the ratio of reducing sugars to ash, and even more patently with the ratio of ash to non-sucrose (non-pol).

The reporting of complete analyses (sucrose, reducing sugars, ash and moisture) of the commercial sugars produced, either raw or higher grade, is made optional.

Acidity and Alkalinity; pH.—Although the determination of titrated acidity and alkalinity is still practised to some extent in juice clarification, it is now generally accepted that p.H values are of greater importance in factory operation than titration figures. The Committee recommends the reporting of pH for hot limed juice, clarified juice, and syrup.

Lime Salts in Clarified Juice.—These need not be reported for international comparisons.

Suspended Solids.—The Committee has decided that these need not be determined (see discussion under "Corrections when juice is Weighed", page 43, and "Corrections when Juice is Measured", page 43; also "Suspended Solids in Mixed Juice", page 61, and "Suspended Solids in Final Molasses", page 62).

Turbidity, or Clarity.—These need not be reported, for either clarified juice or sugars.

Sulphur Dioxide.—This need not be reported, for either juices, syrups, or sugars.

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CALCULATED FIGURES. Purities.—Since the Committee has decided that the control

be based on sucrose rather than pol, it logically follows that gravity purities are to be reported wherever sucrose values are required. However, as it may take some time, for practical reasons, until sucrose figures are determined universally, it will be necessary for all factories which use the sucrose basis to make reports also on a pol basis, giving both gravity and apparent purities, sucrose and pol balances, etc.

Ratios of Reducing Sugars or Ash to Other Constituents.—The Committee recommends that no such ratios be reported except in the case of final molasses, where the R.S.-Ash Ratio, and the Ash-Non-Sucrose (and Ash-Non-pol) Ratio should be shown for reasons given above.

Purity of the Filter Cake.—This is to be reported; the pol is divided by the dry substance.

Weight of Dry Substance in Filter Cake, per Square Metre of Filtering Surface, in 24 Hours.—This figure is one of the best for comparison of filter press results, but concerns efficiency of mechanical operation rather than chemical control. There are other objections to it, and the Committee has decided to omit this figure.

Difference between Non-pol in Mixed and Clarified Juice, per cent, of Non-pol in Mixed Juice.—This figure has been abandoned in Java, where it was formerly in use. It is not to be reported.

Purity Change from Mixed Juice to Syrup.—This figure may be readily ascertained from data to be reported, and there is no need to report it separately.

Deterioration Factor, and Dilution Indicator.—Since sucrose and dry substance are to be reported for sugars not returned to process, these data can be readily calculated if desired, and they need not be reported as such.

Sugar and Molasses in Process.—The possible error in estimat-ing the quantities of stock is relatively large, and for this reason a certain latitude is permissible in determining sugar and molasses in process. The logical procedure is to express these in terms of the products as they are actually turned out by the factory in question. The s-j-m formula or an equivalent one may be used, but the calculation should be made on the basis of gravity purities wherever possible. For the purity of the initial material tha t actually determined is always taken, and for the purity of the sugar and molasses that observed to date.

Balances.—For reasons repeatedly stated, sucrose balances are preferable to pol balances. However, until sucrose figures become

31

available everywhere, those factories which determine sucrose should report both sucrose and pol balances. The Committee recommends that only one basis be used, viz., sucrose (pol) in cane, and that balances on sucrose in mixed juice, or on cane be omitted. Only the weights of the different products are to be reported on the basis of cane ground (see p. 28).

Balances of Brix, standard sugar, non-sucrose (non-pol), etc., are often useful for individual factories, but need not appear in reports for international comparison.

Recoveries and Yields.

General Definition.—This subject is in a bad state of confusion, because not only the terms used, but also the methods of calculation vary markedly in different countries. The term "recovery" should be restricted to the quantity of sucrose, pol, or standard sugar in the sugar produced, expressed on the basis of sucrose (pol) in the initial boiling house material, while the quantity based directly on cane should be termed "yield". Both recovery and yield must be further specified as shown below.

Boiling House Recovery (Sucrose, or Pol).—This term, also called "retention" in Cuba, used to be generally accepted to mean sucrose (pol) in sugar produced per cent, sucrose (pol) in mixed juice. The Committee recommends that this definition be main-tained, and that the boiling house recovery, as thus defined, be reported, but that it be further qualified by adding "sucrose" or "pol", as the case may be.

It is true that losses in the boiling house occur during other operations besides boiling to syrup and to grain, but nevertheless they do occur in the boiling house as defined by the Committee, and the term "Boiling House Recovery" accords with that conception.

Those countries which have adopted another definition for the term "Boiling House Recovery" should change the term expressing the new definition, in order to avoid confusion. Noel Deerr prefers the term "Boiling House Extraction" to "Boiling House Recovery", but "recovery" is more generally used and is understood to refer to boiling house operation, while the "extraction" refers to the milling operation, having been defined by the Committee as sucrose (pol) in mixed juice, per cent. sucrose (pol) in cane.

Basic Boiling House Recovery.—In order to ascertain what relation the quantity of sugar actually obtained bears to that which under the best possible conditions could have been produced, various systems of calculating "available" sugar have been proposed. The sucrose in the filter cake may or may not be considered available; the purity of the molasses may be that actually observed, or it may be fixed arbitrarily; apparent or gravity purities may be used,

32

etc. To avoid further confusion, the Committee recommends the term "Basic Boiling House Recovery", as defined below, instead of the former "available".

In Cuba the available pol per cent. pol in mixed juice is calculated by the Winter Formula is the apparent purity of the mixed juice. This formula is equivalent to the s-j-m formula, with a sugar purity of 100 and an apparent purity of 28.57 for final molasses. In Hawaii three methods are used to find available sucrose per cent. sucrose in the original material; (1) the s-j-m formula direct, with observed gravity purities for syrup and final molasses; (2) for comparative purposes the same as (1), but with a fixed gravity purity of 30 for final molasses; (3) if only pol data are available for syrup and sugar, these are corrected to obtain probable gravity purities, and the s-j-m formula is applied, with the gravity purity of molasses actually observed, or else assumed. In Natal the s-j-m formula is employed, with observed gravity purities for sugar and for mixed juice or syrup, and with a fixed molasses purity of 45. Still other systems have been or are being used in other countries, but the above examples will suffice for purposes of illustration. The Committee defines the Basic Boiling House Recovery as the percentage of the sucrose in the mixed juice which would be obtained, according to the s-j-m formula, adopting values of 100 and 28.57 for s and m respectively, and for j, the gravity purity of the mixed juice. This figure need not be reported as such.

Actual versus Basic-Boiling House Recovery.—This comparison is generally made on a percentage basis, but the resulting figure is not recommended by the Committee for international comparisons, because these are to be made on the basis of Equivalent Standard Granulated (see below).

Standard Sugar.—It has long been recognized that if any com-parisons are to be made between factories which produce sugars of one type and others producing a different type, recoveries based on sucrose (pol) in the sugar do not furnish a satisfactory criterion. In such a case it becomes necessary to convert the quantity of sugar produced into a mutually comparable equivalent. In some countries this has been done in the past by dividing the recovery by the polarization of the standard sugar chosen, such as 96, and multiplying by 100, the result being considered the equivalent quantity of 96° sugar. This method is obviously incorrect as it disregards the purity of the sugar.

In other systems proposed a standard sugar of given polariza-tion and purity, and a molasses of given purity have been assumed. The actual values of these figures have varied from country to country. Thus, the "Standard Muscovado" of Java was based on a sugar containing 96.5 per cent. pol, 0.7 per cent. moisture (97.18 purity), and on the molasses purity being obtained at the factory

33

in question. As the production of white sugar increased in Java, the Standard Muscovado became unsatisfactory for purposes of comparison, and it has been replaced by "Crystal", which is calculated by multiplying the weight of the non-sugar in the sugar produced by the factor rj (100— r), and subtracting the product from the weight of pol in the sugar; r is the apparent purity of the molasses being turned out by the factory. As another example of a standard raw sugar that proposed by Peck may be cited; this contains 96 per cent, sucrose and 1 per cent, moisture (96.97 purity), and the conversion is to be made by the s-j-m formula, with an assumed gravity purity of for molasses.

Equivalent Standard Granulated (E.S.G.).—This type of standard sugar has been introduced by Deerr, and is defined as the quantity of dry, pure sucrose (100 per cent, sucrose, 100 purity), which could theoretically be obtained from a sugar or other raw material, using the s-j-m formula and assuming a gravity purity of 28.57 for final molasses. This molasses purity is identical with the apparent purity assumed in the Winter formula.

The E.S.G. differs from the Java "crystal" in that gravity purities are used in the calculation, and that the purity of the molasses is fixed. Although objections have been raised against the latter feature it must be admitted that Deerr's proposal furnishes a more logical basis for comparing quantities of different types of sugar than any of the other systems. The actual molasses purities vary considerably from factory to factory, and more so from country to country, but all can strive to exhaust their molasses further, and the low standard purity chosen is an incentive in that direction. The Committee has therefore recommended Deerr's "Equivalent Standard Granulated", as above defined, for adoption.

Boiling House Recovery, E.S.G.—This is calculated in the same way as the Boiling House Recovery (p. 32), except that the quantity of Equivalent Standard Granulated corresponding to the sugar produced is substituted for the sucrose in sugar produced. The Committee has decided that this figure be reported.

Basic Boiling House Recovery, E.S.G.—This is the same as the Basic Boiling House Recovery, as defined on p. 32, since it is expressed as 100 per cent, sucrose. It need not be reported as such.

Boiling House Performance.—This figure, also introduced by Deerr, is calculated by dividing the Boiling House Recovery, E.S.G., by the Basic Boiling House Recovery (Sucrose), and multiplying by 100. It is similar to the Winter Rendement (crystal) reported in Java, but in the latter case observed apparent purities are used in the calculation.

In Java the relation between crystal produced and available crystal is also expressed as a percentage loss figure ("Loss in avail­able crystal per cent, pol in mixed juice") rather than as a ratio.

34

It thus forms an item in the crystal balance. The Committee has voted not to adopt this Java figure because only a sucrose balance is to be reported.

Since a better comparison figure than the "Boiling House Performance", namely, the "Reduced Boiling House Recovery, E.G.S.", has been developed by Deerr, the Committee has decided to make the reporting of the Boiling House Performance optional.

Reduced Boiling House Recovery, E.S.G.—This figure is analogous to the Reduced Extraction (p. 22), and defined as the Boiling House Recovery, E.S.G., that would have been obtained under existing conditions if the factory had worked a mixed juice of a standard gravity purity of 85. It is found in the following manner:

First the "virtual" gravity purity of the molasses, mv, is calculated by the s-j-m formula from the observed gravity purity of the mixed juice, j, and the actual boiling house recovery, E.S.G., Y by the formula

or according to McAllep more simply

The value of mv is then substituted in the formula

This formula may be alternatively expressed, without reference to virtual purity of molasses-

where r85 denotes the Reduced Boiling House Recovery, E.S.G. It is a measure of the performance, and may be used directly for international comparisons. It should be emphasized that all purities are gravity purities, and that the recovery is expressed as Equivalent Standard Granulated, as previously defined. The Committee has decided that this figure be reported.

There is an old saying in the medical sphere that if there are many remedies for a complaint, none of them is entirely satisfactory. Similar conditions seem to apply to methods of expression of the standard of efficiency of the boiling house. In his contribution to the I.S.S.C.T. in 1950 (Proc. 7th Congress) S. N. Gundu Rao discussed six recognized efficiency indicators and went on to propose a seventh -which he had derived and which he recom­mended for adoption by the Committee. Gundu Rao's Reduced Boiling House Recovery is based on reasoning mainly parallel to that adopted by

35

Deerr but with a critical difference in regard to the treatment of losses of sucrose other than in the molasses. For full details readers should consult the article referred to above.

The formula proposed by Gundu Rao was—

where r — actual boiling house recovery E.S.G. m — gravity purity of final molasses. j = gravity purity of mixed juice. R — Reduced Boiling House Recovery at juice purity 85 (Gundu

Rao). Prior to the 1953 Congress of the I.S.S.C.T. the various sub-committees

were asked to express preference as between the formulae of Deerr and Gundu Rao. The replies showed that seven out of fourteen favoured the Gundu Rao formula either as an alternative or an addition. Some of the other replies were non-committal and it could be claimed that the majority of definite opinions favoured the Gundu Rao formula.

Doubtless the question prompted the contribution on the subject by K. Douwes-Dekker (Proc. I.S.S.C.T. 8th Congress, 1953) which emphasised the effects of the composition as well as the quantity of non-sucrose in mixed juice. At the meeting of the Committee this feature appeared to be pre­dominant in the thoughts of the delegates and the unanimous decision to retain the Deerr formula may have been influenced by this. One feels that the attitude was that, in the face of a glaring weakness in all available formulae, small differences of reasoning were not critical and did not warrant revision of the existing system—"until such time as a formula which took into consideration the composition of the non-sucrose was developed". (J. F. Williams, Proc. I.S.S.C.T. 8th Congress, 1953, 702).

Overall (Total) Recovery (Sucrose or Pol).—This expression is analogous to the Boiling House Recovery, but referred to sucrose in cane instead of sucrose in mixed juice. It appears in the sucrose balance per cent, sucrose in cane, and is therefore to be reported.

Basic Overall Recovery.—In Cuba the Available Boiling House Recovery (pol) is multiplied by the pol extraction actually obtained to arrive at the available overall recovery. This is based on the assumption that the extraction figure cannot be bettered. In other countries a theoretical 100 per cent, extraction is employed, in conjunction with the actual or a fixed molasses purity. The Com­mittee has decided not to report any Basic Overall Recovery or to make any comparison between the actual and basic values, because a much better and simpler system for comparing overall performance has been suggested by Deerr, as shown in the following paragraph.

Reduced Overall Recovery, E.S.G.—This figure is simply the Reduced Extraction, em12 5> multiplied by the Reduced Boiling House Recovery, E.S.G., r85, and the product divided by 100. This is easy to calculate, and has been recommended by the Committee for adoption.

Yield.—-This expression, without further qualification, is generally taken to mean "Commercial" sugar produced per cent.

36

cane, without regard to the composition of the sugar, and it is therefore of no value for international comparisons of control data, unless further specified.

It is the reciprocal of "tons cane per ton commercial sugar". If any technical comparisons are to be made the yield, like

the recovery, must be converted into terms of a standard sugar. Besides the methods for calculating yields, mentioned on p. 32, various others are in use in some countries, more particularly in connection with payment for cane and field distribution. The yields thus calculated are usually derived from the composition of the first expressed juice. There is no need to discuss these formulas because the Committee has decided not to recommend any of these methods, but to leave this matter to individual countries.

However, since the overall recovery is referred to sucrose in cane, and the yield to cane, the first can readily be converted into the second by multiplying by per cent, sucrose in cane and dividing by 100. The Committee has recommended that the Overall Recovery, E.S.G., and the Reduced Overall Recovery, E.S.G., be thus converted into the corresponding Yield of E.S.G., and Reduced Yield of E.S.G., respectively.

Molasses Produced, versus Molasses Calculated.—A figure of this nature is reported in Hawaii and in Java. In Hawaii only the molasses produced as such is considered, while in J ava the molasses to be obtained from the sugar is also counted. The simplest formula is one of the two employed in Hawaii. The weight of solids in the actual molasses is divided by the difference between weight of solids in syrup and weight of solids in sugar produced. The second formula differs from the first only in that , instead of using the solids in sugar actually produced, the solids in sugar to be produced are calculated by the s-j-m formula.

In Java the molasses obtained per cent, ofj that calculated is based not on solids, but on non-pol, and the figure is also termed "non-pol in molasses per cent. non-pol in clarified juice". The weight of non-pol in molasses is weight of Brix minus weight of pol, in sugar plus molasses. The weight of non-pol in clarified juice is arrived at in the same way, taking the difference between weight of pol in mixed juice and weight of pol in filter cake as the weight of pol in clarified juice, and calculating the weight of Brix in the clarified juice from the weight of pol and the puri ty of the clarified juice. The Java figure appears better than tha t used in Hawaii because it is based on non-pol and because it takes the molasses film on the sugar into consideration. But it should be based on non-sucrose rather than non-pol, and all determinations of gravity solids should be made at equal concentrations of non-sucrose." The figure is really more valuable as a check on the accuracy of the control data of an individual factory than it is for international comparisons. For this reason the Committee considers it unnecessary to report it.

37

Non-pol in Molasses per cent. Non-pol in Mixed Juice.—This figure is used in Java in conjunction with the preceding one, to judge the result of clarification. It is not of sufficient importance for international comparisons, and the Committee has decided to leave it out.

Comparison Figure of the Java Experiment Station.—The original method used in Java to calculate the so-called "Technical Result" started with the premise that, if there were no non-sucrose, all the sucrose present could be obtained as crystal, barring losses inherent in the manufacturing process. The impurities are held responsible for the reduced recovery, and a factory is doing better work, other conditions being equal, if the crystal loss per cent. impurities in mixed juice is smaller. Apart from undetermined losses, this crystal loss may be divided into three separate entities, namely, sucrose lost in molasses, sucrose (pol) lost in filter cake, and crystal lost in sugar, all in per cent. of non-pol (better non-sucrose) in mixed juice. It is admitted that the nature of the impurities, although known to influence the result, is not taken into consideration. The advantages of the figure calculated on this basis are summarized by Sijlmans as follows: It is to a certain extent independent of the purity of the mixed juice; it is practi-cally independent of the undetermined loss; it is not greatly affected by errors in stock-taking; each of the components whose sum it represents can be used to trace unusual losses; the "normal" comparison figure for any clarification process employed, such as simple defecation, sulphitation, or carbonatation, can be readily ascertained from actual average results. A disadvantage of the figure is that it is influenced by errors in the weight of the molasses, but these can be traced from other data, and taken into account.

As the crystal loss per cent. non-pol in mixed juice does not take the undetermined loss into consideration, the two must be combined into one figure to serve as a basis for comparisons. For this reason the crystal loss per cent. non-pol in mixed juice is referred to 100 pol in mixed juice, at an apparent juice purity of 85, and the undetermined loss per cent. pol in mixed juice is added to that figure. The sum of the two gives the "Technical Result".

In 1932 the Java Experiment Station abandoned the method just described in favour of a new one which according to Honig is calculated as follows:

The observed loss in the boiling house is compared with the basic loss found by the Winter Formula, both loss figures being referred to pol per cent. mixed juice. The difference between the observed and the basic loss, subtracted from 100, gives a com-parable figure of boiling house performance which is independent of the purity of the mixed juice, unlike the Winter Rendement, or Hawaiian method No. 2 (p. 33).

The components of the observed loss are (1) the result of clarification, that is non-sucrose (non-pol) in total molasses per cent. non-sucrose (non-pol) in mixed juice; (2) the molasses purity, that is sucrose (pol) in molasses per cent. non-sucrose (non-pol) in molasses; (3) the purity of the mixed juice, that is sucrose (pol) in mixed juice per cent non-sucrose (non-pol) in mixed juice; (4) pol in filter cake per cent. sucrose (pol) in mixed juice; (5) the undetermined loss (sucrose or pol) per cent. sucrose (pol) in mixed juice.

(1) times (2) gives sucrose (pol) in molasses per cent. non-sucrose (non-pol) in mixed juice. (1) times (2) times (3) gives the loss in total molasses, that is sucrose (pol) in total molasses per cent. sucrose (pol) in mixed juice. Finally, loss in total molasses plus loss in filter cake plus undetermined loss gives the total observed loss in the boiling house. In this way the part played by each of the components mentioned above in the total boiling house loss may be ascertained. Total molasses is the molasses weighed plus that in the commercial sugar. This makes it necessary to calculate the equivalent standard sugar with the observed molasses purity.

Neither the old nor the new Java method for figuring the technical result is simple by any means. If any one wishes to make the necessary calculations he can easily do so on the basis of the analytical data to be reported. But from the standpoint of simplicity the Reduced Boiling House Recovery, E.S.G., is to be preferred, and the Committee has decided to omit the Java "Technical Result."

Molasses Factor.—This figure gives the sugar lost in molasses per cent. non-pol in mixed juice. It constitutes the first component of the old comparison figure of the Java Experiment Station, namely, sucrose in molasses per cent. non-pol in mixed juice. In Cuba the molasses factor is calculated by the formula

where D is the pol in molasses per cent. cane, E is the pol extrac-tion per cent, cane, and F the apparent purity of the mixed juice. The Committee has recommended that this figure, as calculated by the Cuban formula, be reported, but with sucrose figures and gravity purities.

Data on Boiling House Equipment and Capacities.—The Com-mittee recommends that the total rated capacity and also the following separate data be reported, per metric ton of cane ground per hour of actual grinding time: the capacity of clarifiers, pans, and crystallizers, in hectolitres; of the filter station, in square metres of filtering surface; of the heaters, evaporators, and pans, in square metres heating surface; of the sulphur oven, where used,

39

in square metres effective surface; also number, size, speed, and square metres of screen area of the centrifugals. In reporting heating surfaces, it should be stated whether the outside or inside surface is referred to.

l

CHAPTER V

Methods of Weighing and Measuring

The products to be weighed or measured have been enumerated in Chapters I I I and IV. The present chapter deals with the methods for ascertaining the quantity of each. The Committee has decided to lay down only general rules to be observed in these operations because local conditions impose well recognized restrictions on the applicability of given methods or apparatus and this state of affairs will probably continue for years to come. Moreover, in many instances methods or apparatus may differ and yet be equally good, the choice depending largely on personal preference. For these reasons general principles are emphasized in this chapter and details omitted, but in some cases certain devices that have been found of special merit are briefly described.

Sys tem of Weights and Measures. At the Soerabaja Congress, held in 1929, the Society at large

expressed itself unmistakably as favouring the metric system for international comparisons. The difficulties in the way of its general adoption are well recognized, but it is the only logical one as long as all civilized countries adhere unquestionably to the decimal system of numbers. The technologist should be the first to shake off the fetters of the interconversion of the innumerable local systems and to use one international system of weights and measures for mutual comparisons. The customary local units may be given in parentheses if desired. Tables for converting the principal local units used throughout the sugar cane world are assembled in Appendix I.

General Considerations.

The standard practice for determining the quantities of the various products, except in stock taking, is actual weighing. Measuring should be resorted to only as a necessary evil until scales have been installed. But even measuring is to be preferred to calculation from analytical figures. Scales of measuring apparatus should preferably be provided with recording devices to minimize errors.

Calibration of Scales.—All weights and weighing machines should be checked at regular, frequent intervals with official standard weights.

Calibration of Tanks.—Measuring tanks used where scales have not yet been installed should be calibrated by weighing the water

41

required to fill them or that obtained upon emptying the completely filled tank. The weight found is converted into the corresponding volume by multiplying by the specific volume of the water at the temperature noted during the operation.

For purposes of stock taking the tanks, pans, crystallizers and other receptacles are calibrated by internal measurement, and tables are prepared which show the volume ("in" or "out") at any given level.

Weighing of Cane. Cane should be weighed immediately before being crushed.

To this end cane scales should be placed as closely as possible to, and preferably directly in front of the cane carrier. They should be balanced empty several times a day. The weight of the cane is determined by deducting the weight of the vehicle from that of cane plus vehicle. The tare weight of each vehicle must be accurately known, and frequently checked; it must always be redetermined after repairs. For purposes of factory control no correction whatever is to be applied to the weight of the cane actually found even though a deduction may be made in accounts with cane planters.

Weight of Field Trash. This is determined only for the purpose of ascertaining fibre

per cent. cane and only in those countries where the weight of the bagasse is derived from the latter figure. The Hawaiian method5

has been recommended by the Committee. It is described as follows:

"The total amount of field trash cannot be weighed directly, but must be estimated by determining the actual weight of trash contained in representative cars of cane. This should be done as often as feasible, preferably each day but at least once a week. The field trash can be determined by separating the trash from the cane in a full car, and weighing each separately. The percentage of trash is then calculated on the combined weight of clean cane and trash."

"Field trash determinations should be so conducted that the loss in weight through evaporation during the operation will be reduced to a minimum. For this reason it should be completed as expeditiously as practicable, and if possible should be conducted in a place protected from sun and wind."

The weight of trash must under no circumstances be deducted from the weight of the cane entering the factory.

Weighing of Mixed Juice. As the factory control is largely based on mixed juice, very

particular care must be taken in ascertaining its correct weight. The mixed juice is to be weighed before the addition of any chemicals.

42

Various types of scale for the weighing of mixed juice are now available, and incorporate several different principles of batch weighing. The majority are of the beam balance type, but at least one hydrostatic pressure type is on the market. Of the beam balance types, some depend on the tare of the empty weigh tank to remain constant, others drain the tank down to a fixed or measured tare weight; some aim at exact repetition of the weight of juice discharged each cycle, others isolate an approximate measure of juice in the weigh tank and proceed to weigh it accurately.

Under the circumstances it is impossible to lay down other than general rules for the maintenance of juice scales. Mechanical parts should be kept clean and in good order, the scales should be tested frequently by dead weight test under conditions closely simulating normal operation, and counting, printing or recording mechanisms should be checked regularly.

Measuring of Mixed Juice.—Where this is still necessary, in the absence of juice scales, it must be subject to absolute control. The tanks should have a sloping bottom and be arranged so that any leaks through valves, plugs, etc., are immediately detected. The tanks should be constructed of heavy material and in such shapes that the walls and bottom will not bulge out from the weight of the juice. The tanks should always be filled to the same level, and to this end provided with an overflow pipe. They should discharge into another tank from which the juice goes to the clarification station. The number of tanks filled must be carefully recorded, preferably by an automatic device. If the juice is measured in the liming tanks, the volume of the milk of lime added must be deducted. To convert volume of juice into weight, the volume is multiplied by the specific gravity of the juice at the temperature of the juice when measured.

Corrections when Juice is Weighed.—In Java the weight of the juice is corrected for suspended matter. This atti tude is the scientifically correct one because the subsequent analysis applies to juice freed of coarsely suspended matter. Nevertheless, the Com-mittee has decided against this correction, for practical reasons. The weight of the mixed juice is to be reported as gross weight. If the correction is applied, however, the juice weight thus found is to be reported as net weight.

Corrections when Juice is Measured.—In this case a correction must be applied for the volume of the gases occluded in the juice. The Committee recommends for this purpose the methods used in Java. In the simpler, but less accurate method, a tank of known volume and of about the same dimensions as the measuring tank is filled with the mixed juice, which is then allowed to stand until the foam has broken and the air bubbles have risen to the surface

43

This requires about one half to one hour. Then water is added from a measure until the tank is filled again to the original level. The volume of the water added, in per cent. of the total volume is the foam correction. A better method, to be preferred to the one just given, is that described by Prins6 and improved by Bedding.7 Briefly, the method consists of determining the specific gravity of the mixed juice, d1, as it comes from the mill, by a hydrostatic device installed in the measuring tank, at the same time measuring the specific gravity of the de-aerated juice, d2, in the laboratory at the same temperature, and calculating the foam

correction by the formula For the details of the

method the original articles should be consulted.

The correction for suspended matter is omitted, as stated under the preceding heading.

Weighing of Clarified Juice. In those factories where the weight of the mixed juice cannot

be ascertained, e.g., where milling and clarification form a compound system, the weight of the clarified juice must be determined. Measuring is inadmissible in this case because the large temperature correction required may lead to serious errors.

Weighing of Bagasse. Bagasse weighing is still in the experimental stage, but it is

to be hoped that a practical device for this purpose will come into use in the near future.

Weighing of Imbibition Water. This should be done by means of tank scales, the same pre-

cautions being observed as in the weighing of mixed juice. Great care must be exercised in this operation, as the weight of the imbibition water is used to find that of the bagasse, except where the latter is calculated from fibre per cent. cane, determined directly. The weight of the imbibition water must include any and all water entering the juice during the milling process.

Measuring of Imbibition Water.-—This is not recommended, but where no scales are available it must be resorted to for the present. The same precautions must be observed as in the measur-ing of mixed juice. Correct temperature measurement is par-ticularly important. Ordinary water meters are unreliable.

Weighing or Measuring of Filter Washings and of Muddy Juice Returned to the Mill.

Where such return is practised the weight of muddy juice must be determined directly, as recommended for the weighing of

44 i

mixed juice. Filter washings should also be weighed in the same manner, but they may be measured if necessary under the same conditions as specified for mixed juice.

Measuring of Milk of Lime Added. This is required only when the juice is measured by volume

after addition of the milk of lime. The actual measuring is such a simple matter that the exact procedure may be left to individual countries. The undesirable tendency of milk of lime to form crusts on the walls of the vessels must be duly considered. An inexpensive and effective device, used in Java for measuring milk of lime, is recommended. It consists of a cylindrical vessel with conical bottom, in the lower end of which is mounted the discharge pipe, with a plug valve. The inlet pipe, with the same kind of plug valve, ends just above the vessel, in line with the discharge pipe. The two valves are actuated simultaneously by an interlocking device so that one is completely open while the other is completely closed. An overflow pipe, of larger diameter than the inlet pipe, is attached to the vessel, and its height can be regulated by a screw movement. The milk of lime in the Supply tank must be kept in constant motion and circulated through the supply pipes.

Weighing of Filter Cake. Weighing of the entire cake, dumped into cars, is recom-

mended. A small platform scale with recording mechanism is best for this purpose. I h e weight of the empty cars must be determined each time, or frequently checked. Care must be taken that no washings are included with the cake.

If weighing of the entire production is not practicable it is necessary to resort to sampling methods. With filter presses the preferred method is to weigh one or more representative cakes from each press and to expand each average weight in proportion to the number of frames in each press and the number of cycles involved.

The weight of cake discharged from a rotary filter is commonly determined by calculation from samples involving a definite area of screen surface. At regular intervals the cake adhering to one whole frame may be removed and weighed. At the end of a period the average weight of cake is multiplied by the number of frames on the drum and the number of revolutions in the period. As an alternative a sample may be isolated by a cutter enclosing a known area. The portion removed is weighed in common with others taken similarly at intervals. The average weight of the known area may be related to the output of the whole filter over a given number of revolutions.

When other types of filter are involved the method of deter-| mining the weight of the cake as accurately as possible must be

45

left for the present to individual countries or factories. In the case of Sweetland, Kelly, or similar presses the thickness of the cake may be measured, the specific gravity determined, and the weight calculated from these data. In some cases calculation from analytical data must be resorted to, but the possible error of this method may exceed 20 per cent.

Estimating the Quantity of Material in Process. Whether the stock on hand is estimated during a shutdown or

during full operation, the following general principles must be observed. The weight per unit volume must not be based on Brix obtained after dilution with water. Juices and syrups can be spindled at their original density, and the specific gravity at the temperature of measurement found from tables. For massecuites and molasses the weight per unit volume must be determined directly, by using a wide mouth pycnometer, or by filling a bottle or box of known volume with the material and weighing it. The apparent specific gravity or apparent Brix must be determined, or converted into the weight per volume, at the temperature observed for the material whose quantity is being estimated.

Weighing of Final Molasses. Scales of large capacity should be used for this purpose, in

order to reduce the number of weighings to a minimum; recording scale tanks are to be preferred. Tare weights must be determined at each weighing. If molasses is shipped in tank cars a valuable check on the original weight of the molasses may be obtained by weighing each tank car empty and again after filling.

Measuring of Final Molasses.—-The Committee considers this method of arriving at the weight of the molasses as inadmissible for control purposes. Where scales are not available they should be installed as soon as possible. A rough estimate of the quantity of final molasses may be obtained by the same methods as are used for estimating molasses in process. The pneumercator which measures the hydrostatic pressure of liquids in tanks, independently of foam or occluded gases, if a useful device for ascertaining the quantity of molasses in storage tanks, but for the purpose of running factory control it cannot replace actual weighing directly after purging.

Weighing of Sugars. For this purpose the Committee recommends the directions

given in the Hawaiian Book of Methods,5 which are as follows: "When sugar is weighed with an automatic scale, the weight

should always be checked on an accurate platform scale at the beginning of a strike and at intervals thereafter during the strike. When it is weighed on a platform scale the counterpoise should be

46

set at a point corresponding to the weight of the standard sugar weight plus the average weight of the container. The average weight of empty bags is best obtained by weighing fifty or a hundred bags, since individual bags are likely to show appreciable variation from the average. All scales should have frequent attention in the matter of cleanliness. The beam and counterpoises should be frequently cleaned by steaming, to remove lint and dirt, and should then be oiled with a light oil to prevent rusting. The platform should be kept clean by scraping and occasional washing. It is advisable to check the weight of the sugar by weighing the loaded sugar cars where this can be done."

Measuring of Condenser Water.

The quanti ty of condenser water must be known if the sugar loss by entrainment is to be determined quantitatively. The Committee recommends for this purpose a water meter in the supply line, or a weir in the discharge flume. Where neither of these is available, the Hawaiian method5 of calculating the quantity of condenser water is recommended. The description of this method is too length to be reproduced here in detail. Briefly, it is based on the following principles. The water evaporated in the effets is calculated from the weight of the initial juice, and the Brix of the syrup and of the original juice in the usual manner. The percentage proportion of the total evaporation that is obtained in the last body of the effet is determined by actual test, and the tons of water evaporated in the last body is thus arrived at. Next, the pounds of condenser water per pound of vapor condensed are calculated from the heat content of the vapour, in B.T.U. or Calories per pound at the vacuum employed in the last body, the tempera-ture of the injection water and the temperature of the discharged water. The result is multiplied by the tons of water evaporated in the last body, as found previously, and the product gives the tons of condenser water for the time period in question. The

. evaporation in vacuum pans is more difficult to compute because of the great variation in the rate of boiling; calculations are pre-ferably based on data obtained by the use of flow meters on the steam lines.

Under normal conditions the sugar lost in condensate is too small to have more than a negligible effect of the control figures, but it must nevertheless be carefully watched.

Measuring of Water Used for Other Purposes.—The quantities of water used in presses, pans, and centrifugals are of no importance for the regular factory control and there is no need to determine or report them.

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CHAPTER VI

Methods of Sampling

General Remarks. Samples must be truly representative because otherwise the

most carefully conducted analysis is practically worthless. Where the operation is continuous it is best to collect a continuous sample, always in proportion to the quantity of the material being sampled. Automatic sampling devices which fulfil these conditions should be used wherever practicable. If continuous sampling is impossible, proportional samples should be taken at regular, frequent intervals. All sampling devices must be kept clean and in perfect working order to prevent contamination of the sample or irregularities in sampling. Automatic samplers are subject to mechanical break­down, and for this reason manual sampling has been found preferable in some countries and under certain conditions, but it requires strictest supervision.

Cane. This is sampled only where the fibre per cent. cane is deter­

mined directly to calculate weight of bagasse. The Committee recommends the procedure prescribed in Hawaii,5 which is as follows:

"Several samples of cane for fibre determination should be taken daily, the number necessary depending on how much the cane varies in fibre content. The sticks comprising the sample should be taken at random, care being taken to avoid selection. Sample by fields when the weight ground from each field is known, taking several sticks either from the cars or the cane carrier. Nine sticks make a convenient sample. In lieu of this, at regular intervals take three or four sticks at a time from the carrier, place in a cool, shaded place and allow the sample to accumulate until the end of the sampling period. Subsample down to a convenient number of sticks."

A more elaborate system of sampling cane is in use in Queens­land.8

Field Trash.— This is also sampled only where fibre per cent. cane is determined directly. The total quantity of field trash obtained when its weight is determined (see p. 42) is used as a sample.

Sample Containers for Juices, etc. Seamless containers of enamel ware, preferably white inside,

with well rounded shoulders, and provided with tight fitting covers

48

are recommended. Glass is less advisable, except for containers kept in the laboratory, on account of breakage. All containers should be cleaned, sterilized, and thoroughly dried every time after they are used, and the proper amount of preservative placed in them before the sample is added. Two sets of containers should be provided so that one may be cleaned and disinfected while the other set is in use. Containers for different types of juices should be easily distinguishable by differences in shape, outside colour, or other easily recognized permanent markings.

Mill Juices .

In the control scheme recommended by this Committee only mixed juice—and until a practical method of direct Brix determina­tion in bagasse is developed, last expressed juice—need be sampled. But the general methods recommended may be applied judiciously also to the sampling of juice from single crushing units or combina­tions of them where corresponding analyses are desired.

Mill juice samples may be taken from the juice canals by means of automatic samplers. The best of those described in the various books of methods is the one used in Java. It consists of a compound ladle which samples across the entire width of the canal and down to the bottom of it. The ladle alternately dips into and is lifted above the canal being actuated by a mill roller shaft, and in the upper position discharges the sample through the hollow shaft to which the ladle is attached. Ladles should be changed and sterilized every hour. Baffle plates or similar con­trivances to assure perfect mixing should be placed in the canal. The effectiveness of these devices should be tested by analyses. If samples of juice from only part of the milling plant are to be taken from canals, these must be specially constructed, as prescribed in J ava. The Westcoatt spoon sampler (Hawaii) and the Mercedita sampler (Cuba) are similar in principle to the Java device, but having only a small sampling spoon or cup do not sample over the entire cross-section of the canal.

In the case of mixed juice it is often more desirable to do the sampling at the time when this juice is being weighed (or measured). This may be done automatically by means of the Baldwin sampler,9

the Conklin sampler,5 or some similar device; or a sample may be taken by hand from each tank as it is being discharged.

The ordinary so-called wire sampler which intercepts the flow of juice at some convenient point and diverts a thin stream or trickle into the sample container is not to be recommended because in hot countries there is always danger of slight concentration by evaporation which may easily raise the Brix more than the per­missible limit of error. Sampling devices with narrow pipes or pet cocks should not be used for mill juices as they foul too easily and are difficult to keep clean.

49

In the absence of automatic devices samples arc to be taken by hand at regular frequent intervals.

Last Expressed Juice.—The last expressed juice, i.e., the juice the purity of which is used to calculate the Brix in bagasse, should be sampled from the bagasse roll of the last mill. The sampling should be done by hand and should be synchronized with the sampling of the corresponding bagasse. The sample must represent the juice falling from the entire width of the roller. If, however, the performance of the different mill units is required the combined juice from the front and back roll of each mill is sampled.

Preserving Juice Samples. There is such a diversity of opinion in the different countries

on this important point that the Committee has decided to leave the choice of preservatives for the present to each individual country. As a guide, the practice in some of the more important countries is described. J ava employs 100 mg. of mercuric chloride (not medicinal tablets containing sodium chloride) for each litre of juice, but it is noted that for complete sterilization larger quantities are necessary. Cuba and Puerto Rico recommend mercuric chloride only for the sample to be used for the Brix determination, at the rate of 0.5 ml. of a saturated solution (about 35 to 40 mg. of HgCl2) per litre of juice; this is stated not to affect the Brix of the juice. Hawaii uses mercuric chloride only in samples for the determination of reducing sugars, at the rate of 250 mg. per litre of juice. Since mercuric chloride coagulates protein, Natal and Mauritius prescribe a solution containing 95 g. mercuric iodide, 50 g. potassium iodide, 40 g. formalin, and 200 g. of water; 0.2 to 0.5 ml. of this solution are added to each litre of juice. Hawaii, India, Japan and Philip­pines use formalin in samples for both Brix and pol determination 1 ml. per litre of mill juices, and 0.5 ml. for clarified juice, filtered juice, and syrup under 60 Brix. But formaldehyde has been proven to be rather unreliable. For pol determinations Cuba, Louisiana, Natal, and Puerto Rico recommend Horne's dry lead, and this has been found to be cjuite satisfactory. Mauritius prefers dry neutral lead acetate because it does not affect the rotation, while siibacetate does. Olivier has reported that juices preserved with dry neutral lead acetate, if filtered at once after clarification, undergo no deterioration in 12 hours or more, but that, if the juice is left in contact with the precipitate there is decided decomposilaon in less than six hours.

It is generally preferable to use the same preservative for both Brix and pol determinations because samples treated with different preservatives may not be quite equivalent.

It is generally accepted nowadays that refrigeration provides excellent protection against deterioration of juices held in storage. Storage at domestic refrigerator temperatures of 35 to 40° F.

50

(1 to 4° C.) is quite effective for days, but if the holding period is to be extended to weeks or months frozen storage is to be preferred. If the original composition of the product is to be maintained unaltered precautions must be taken to prevent change of water content. On the other hand, if only the solids are to be preserved the product may be dried by sublimation of the water from the frozen material, and the dehydrated residue may be stored safely for extremely long periods.

B a g a s s e .

Because of the non-uniformity of this material special care must be exercised to sample across the entire width of the roller and through the entire depth of the bagasse blanket. A continuous automatic sampler fulfilling these conditions would be best, but it is yet to be designed. An automatic device, used in Java, which samples all the way across the carrier, but not necessarily through the entire bagasse layer, consists of a trap hinged to the underside of the carrier bottom (rake carrier used), and actuated by the carrier chain. A similar t rap sampler, built into the bagasse chute, is recommended in Puerto Rico. Two other automatic devices, used in Java, which mechanically pick up bagasse samples by means of ladles attached to a rotating drum, or of small bucket elevators, sample only at three places across the blanket. It is true that they could be constructed to sample at a larger number of points, but they are cumbersome, costly and require much labour to keep them in perfect working condition.

If the samples cannot be taken automatically, the next best way is the method used in Hawaii and Puerto Rico, where a V-shaped trough, as long as the roller, is held under the edge of the lower scraper. A similar device has been recommended in Queens­land, where the question of bagasse sampling has been studied by Behne.10 If reliable help can be obtained, samples may be taken by hand. This must be done systematically, at short distances across the entire blanket and down to the bottom of it, without tendency toward selection, and most important of all, at regular frequent intervals.

As bagasse samples dry out and deteriorate rapidly they must be placed and transported to the laboratory in closed containers, and analysed as soon as possible. Deterioration may be largely prevented by placing a cotton wad or sponge, moistened with preservative, in a perforated holder in the cover or bottom of the sample container. Either ammonia alone, or better, a mixture of it with formalin, or one containing six parts strong ammonia and one part chloroform, may be employed as a preservative.

Bagasse samples must be mixed as rapidly as possible when they are collected, and if subsampling is necessary the moisture loss

51

occurring during this operation must be determined and corrected for. The containers must be thoroughly cleaned and disinfected after each use.

Milk of Lime. The sampling of this material for determination of its density

is a simple matter and requires no special directions.

Clarified Juice. Ordinarily this juice is best sampled continuously, for instance

by placing a pet cock or small pipe with a valve in the discharge side of the pump, in the pipe line conveying the juice, or in the evaporator supply tank. Otherwise intermittent samples may be collected by hand. Precautions must be taken to avoid evapora­tion; this is best accomplished by attaching a condenser to the sample bottle.

For those mills which weigh the clarified instead of the mixed juice, Waddell11 has designed an automatic sampler. There is no possibility of evaporation or contamination of the sample. This sampler may also be used for mixed juice.

Juices Returned from Boiling House to Mill. Where this practice is followed, the Java method is recom­

mended. Proportionate samples are withdrawn from each weighing or measuring tank by hand. One-tenth gram mercuric chloride is added as a preservative for each litre of filter washings, and 250 mg. in the case of muddy juice. Evaporation of the hot filter washings must be prevented by appropriate measures.

Filtered and/or Subsider Juice. If these are to be analysed separately the sampling must be

done as recommended for clarified juice.

Filter Cake. Press cake is most easily sampled by means of a trier, consisting

of a metal tube of convenient length, which is pushed into the cake after it has been dumped into cars, or in situ in the press. A sufficiently large number of triers full must be taken to yield a representative sample. The contents of the trier must be immedi­ately removed, for instance by means of a wooden rod, into the sample container which should be provided with the same preserva­tive as is used for bagasse samples, and should be kept closed when not in actual use. A convenient sampler for sampling cake in the press is recommended by the Sugar Club of Cuba: A short trier is combined with a receptacle large enough to hold the samples from one press; one such sampler should be provided for each press to be sampled.

52

If the samples are taken out of cars, the lower end of the trier should be sharpened, but this should not be done when the samples of the cakes are taken in situ because it would ruin the filter cloths.

In Java it has been found that a perfectly reliable sample of filter cake can be secured only by mixing all the filter cake with water to a homogeneous paste. The mixture of filter cake and water is removed from the factory by pumping. The dry substance must be determined both in the paste and also in the cake sampled directly from the press. The pol of the diluted filter cake is then reduced to undiluted filter cake on the basis of the two dry sub­stance determinations. This method is rather complicated and in some places cannot be applied at all because the disposal of the diluted filter cake is liable to create a public nuisance. The required pumping installation is also an objection.

Various methods are adopted for the sampling of rotary filter cake. One commonly adopted procedure is at regular intervals to cut out a small disc from the mat of cake with the aid of a "biscuit cutter". The weakness of this method is that the operator will invariably select a sample from a frame of good cake and thus a bias may be introduced. For this reason it is preferable to associate the sampling with the weighing. The comparatively large slabs of cake taken for the weight determination may be composited in a closed container for several hours. The composite bulk is then weighed and mixed and a sample of about 1 kg. taken for despatch to the laboratory. Usually no at tempt is made to relate the analysis of a single sample to the weight of cake discharged during the sampling period; the rate of output of cake is sufficiently stable for the analytical figures to be averaged arithmetically over the period between chemical control balances.

Syrup. This may be sampled in the same way as recommended for

clarified juice. Samples may also be taken by hand as the syrup leaves the last body of the multiple effet, or from the storage tanks. An automatic continuous sampler has been described by Waddell.12

Preservatives are not needed if the syrup is of full density and the sample is kept in a cool place or a refrigerator.

Massecuites . Several* samples should be taken at regular intervals as the

strike is being dropped from the pan, and composited in a covered container. Sampling must be stopped before the pan is steamed out. Preservatives are unnecessary.

Molasses Returned to Process . For the pan control the sample is best taken from the tank

in which the molasses is diluted. This is most readily done by means of a "thief" pipe long enough to reach to the bottom of the

53

tank and provided with a device to close the lower end of the pipe before it is withdrawn. Samples taken at only one point in the tank are not representative because the molasses does not readily form a homogeneous mixture. If the diluted molasses is pumped, continuous samples may also be taken from the pump or pipe line, as previously described.

For the control of the centrifugal work, samples may be collected at regular intervals out of the- canal leading from the centrifugals to the molasses tanks. Grab samples should be taken Only when an approximate purity is desired immediately.

Final Molasses . For the control of the crystallizer work the sample should be

drawn continuously or at frequent intervals either from the gutter carrying the molasses away from the centrifugals, or from a pump or pipe line.

For general control purposes it is better to draw samples when the molasses is being weighed, either by hand, or again from the canal, pump, or pipe line carrying the molasses away.

Commercial Sugar. A reliable automatic sampler, used in Hawaii, consists of a

small "turbine" wheel with four curved prongs, mounted in the side of the hopper through which the sugar drops into the bags. The turbine is driven by the downward flow of the sugar, and small samples are swished into a box which is attached tightly to the hopper, but can be removed when the sample is to be taken to the laboratory.

In the absence of automatic devices, a sample is taken with a spoon or other small measure from each bag while it is being filled, and placed in a container which is kept closed as much as possible in order to prevent moisture changes in the sugar. To sample sugar for commercial transactions from closed bags, a trier is used which is pushed into the bag diagonally from the top to the bottom of the bag.

Sugars Returned to Process.—Samples of these sugars may be collected by hand from the conveyors.

Waters. Condenser Water.—A continuous sample should preferably be

taken, through a small pipe with regulating valve, or a pet cock, screwed into the leg of the condenser, or by a valve at the pump; or intermittent samples may be collected at as frequent intervals as conditions indicate.

Boiler Feed Water.—Although boiler feed water does not enter into the control proper, sugar losses may nevertheless be traced through it, and careful supervision is necessary. Samples should

54

be taken automatically and continuously through a small test valve in the pipe line, or by some similar device. Otherwise intermittent samples may be collected at regular intervals. Water samples should be taken from the columns of each boiler after the column has been blown off.

Condensates from Vapour Lines.—To detect entrainment losses, the Java "telltale" equipment is recommended. The vapour pipe is tapped, preferably near the end of a horizontal stretch, and the condensed vapour is collected in a glass bottle or metal container. Details are given in the Factory Control Manual of the Java Sugar Experiment Station.

Drain and Waste Water.—A water wheel placed in the ditch and discharging into a closed bucket is recommended, or inter­mittent samples may be taken at regular intervals. If sugar is found, samples should be taken as often as required until the trouble is corrected.

Gases . Sulphur Dioxide Gas.—Where sulphitation is practised, the

sampling and testing of the gas are best accomplished simultaneously by recording instruments, either electric or of the CO2— recorder type. If recording instruments are not available, an aspirator bottle may be used.

Lime Kiln Gas.—The most convenient devices for carbonatation factories are indicating or recording instruments which both sample and analyse these gases. Otherwise a small pipe may be mounted into the pipe leading from the carbon dioxide pump to the satura­tion tanks; the small pipe is extended directly to the laboratory where a sample may be removed as desired.

Composit ing Samples . This matter should be decided by individual countries, as it is

largely influenced by local conditions. It must be kept in mind, however, that fewer analyses, carefully made without haste upon samples that are scientifically composited, are more reliable than analyses of a large number of individual samples, carried out hastily in a limited amount of time. The compositing of samples should not be left to sample boys, but should be done by trained, responsible personnel.

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CHAPTER VII

Methods of Analysis

General Considerations. The Committee agreed to present in its original report only

the guiding principles for the selection of analytical methods, giving only such details as were necessary to explain the reasons for the adoption of particular procedures. In this present chapter this subject is discussed in greater detail and more definite information is given about the methods recommended. However, in the case of methods that are well known and may be readily found in the generally available manuals it is not considered necessary to include detailed directions.

F ib re . Fibre in Clean Cane.—The direct determination of fibre has

been sanctioned by the Committee as one of the two methods for arriving indirectly at the weight of the bagasse. Fibre has been defined as the "dry, water-insoluble matter in cane". This definition implies the method of determination, i.e., extraction of the finely shredded cane with water until all the soluble matter has been removed, as indicated by the absence of sugar. An essential require­ment is that the cane be shredded fine enough to rupture the cells; otherwise there is danger of incomplete extraction, as shown by Egeter, Khainovsky, and Erlee.

Among the various mechanical devices for comminuting cane there may be mentioned the "Cutex" machine of the Sugar Manu­facturers' Supply Co., 7-8 Idol Lane, London, E.C.3, England, and a machine devised by Noel Deerr and manufactured by the Saran Engineering Co., in India. A similar "fibrator" is used in Australia. The Warmoth-Hyatt disintegrator is recommended in Hawaii, but the use of choppers, meat slicers, or of a common wood plane is also permitted provided that the sample is thoroughly disintegrated before it is subjected to analysis. If there is loss of weight during the preparation of the sample, due to evaporation, this loss must be determined and a correction applied.

The method of analysis recommended by the Committee is based on the official Hawaiian method.5 Transfer the weighed finely divided sample (about 200 g.) to a strong linen bag and tie with heavy thread (twine forms knots which are likely to rupture the bag). Wash in running water until the washings are clear, squeeze out surplus water, place the bag in a heavy canvas bag and press in a screw press. From 600 to 1,000 pounds per square

56

inch is a suitable pressure. The pressed mass is then broken up, the bag examined to see that no holes have been made during the pressing, treat with cold running water for at least two minutes and repress. Five or six alternate soakings and pressings will extract a properly prepared sample. The thoroughness of the extraction may be checked by submitting a portion of the expressed fluid to the alpha-naphthol test or one of the alternative chemical tests for traces of sugar (p. 67). Dry sufficiently that the fibre may be easily removed from the bag, transfer to a tray, removing the particles adhering to the bag by rubbing and dry at 125° C. Three hours of drying should suffice. Weigh quickly to avoid absorption of moisture. Instead of pressing, the sample can be extracted by washing in cold running water for 24 hours.

The method of fibre determination used in Queensland involves immersion in circulating boiling water for one hour, after treatment with cold water. Boiling water is liable to convert pentosans and pectins, which are fibre constituents, partly into soluble products, thus lowering the fibre result. This is avoided in the Hawaiian method recommended by the Committee.

An alternate, indirect method of fibre determination consists in determining the moisture (W) in the shredded cane, the Brix (b) of the absolute juice, and calculating the fibre per cent. cane by the formula: 100 — [100W (100 — b)]. While this method may be useful in certain cases it is not recommended to replace the direct method which is to be taken as the standard.

Fibre in Field Trash.—The trash sample must be chopped very fine as the soluble matter is more difficult to extract than from the cane stalk. A subsample of 50 to 100 grams is analysed in the same way as the clean cane.

Fibre in Gross Cane.—This is calculated from the fibre in clean cane, the fibre in trash, and the percentage of clean cane and trash in gross cane. The fibre per cent. clean cane is multiplied by the clean cane per unit of gross cane, and the fibre per cent. trash by the trash per cent. gross cane. The sum of the two products gives fibre per cent. gross cane.

Fibre in Bagasse.—This is generally calculated as shown in Chapter I I I , p. 25. The result may be checked, if desired, by a direct determination made in the same way as described for clean cane.

Dry Substance. Dry Substance in Cane.—This is directly determined only in the

alternate method mentioned above for indirect fibre determination in clean cane, which has not been recommended as an official method. It is subject to the same errors as direct fibre deter­minations, owing to the difficulty of securing a representative sample of cane.

57

Dry Substance in Bagasse.—The sample should be analysed as soon as possible after being taken, to prevent loss of moisture. The moisture determination is a simple operation in itself and may be carried out in various ways, the principle being to drive out the moisture from a weighed sample of bagasse as quickly as possible and to weigh the dry bagasse. As the moisture is not uniformly distributed throughout the bagasse it is advisable to use a large sample, especially when the bagasse is rather coarse. India and Java prescribe samples of one kilogram. The original Spencer bagasse oven13 takes as much as two kilograms. . The Committee recommends much larger samples than the usual 100 grams, i.e., at least 500 grams. The container for the bagasse should be made entirely or partly of perforated metal or gauze, to allow free access of air. Drying in a current of hot air is much more efficient and rapid than without this aid. The temperature of the oven or hot air may safely be raised to 130° C. without ill effect. The bagasse must be dried to constant weight, and the time required to do this under the conditions chosen must be determined by experiment. Moisture determinations on bagasse should be run at frequent intervals.

Dry Substance in Filter Cake.—Here again as large a sample as can be handled conveniently should be used. It should be spread out in a thin layer, heated at first at a low temperature to prevent the formation of a crust on top, and then to constant weight at 100-105° C.

Dry Substance in High Grade Sugars.—A convenient quantity, 2 to 10 grains according to grade, is dried in a shallow layer at a temperature of 100-105° C, for a specified time which has been found experimentally to give correct results. The International Commission for Uniform Methods of Sugar Analysis has adopted the following method as a standard: Ten grams of sugar is weighed into a metal (aluminium) dish, 2 inches diameter by 1 inch high, with close fitting lid provided with a knob. The sugar is dried in a vacuum oven at 60° C. at a pressure not exceeding 50 mm. of mercury, the oven being bled with a current of dry air. The sugar is left in the oven for 5 hours, weighed, and then dried for further one-hour periods until the loss in weight is less than 1 mg. For routine factory control the Committee recommends the Spencer electric oven in which the drving can be accomplished in 20 minutes at 110° C.

Dry Substance in Juices, Syrups, Massecuites, Molasses, and Low Grade Sugars.—Such determinations are not recommended for routine control work. If they are to be made for special purposes, the following points should be observed. The surface of the material should be increased as much as possible. This may be accomplished by dissolving the denser products in water and absorbing the solution on filter paper, or by mixing it intimately with pure quartz

58

sand, pumice stone or asbestos. The use of the Seidenberg platinum gauze dish14 is based on the same principle. The drying should be done in vacuo at 70, or preferably 60° C. and a pressure not exceed­ing 50 mm. of mercury until the loss in weight after a two-hour drying period does not exceed 0.5 mg.

It has been shown by Spencer that the drying of liquid products can be accomplished rapidly, and without danger of sensible decom­position, in a current of hot air in the electric oven devised by him. Generally, the time necessary for complete evaporation of moisture should be determined experimentally, by comparison with the standard vacuum method. It is usually not possible to obtain strictly constant weight, but a good criterion is the constancy of loss in weight due to decomposition of levulose, etc.

Brix. The general methods for determining Brix by spindle,

pycnometer, hydrostatic balance, etc., are so well standardized that they require no discussion here. A very accurate device for reading Brix hydrometers has been designed by Deerr15; with this instrument very careful temperature control is indispensable, as otherwise the precision becomes illusory.

To minimize errors, Brix readings should be taken with spindles standardized about average local room temperature which in most tropical countries is above the international standard temperature of 20° C. Hawaii and Java use spindles calibrated at 27.5° C, and this point is generally recommended for the tropics; corresponding temperature correction tables are available. Determinations with the pyenometer should also preferably be made at room tempera­ture and the result converted into Brix by calculation or with the aid of tables.

The Brix of juices is to be taken with the usual spindles, but for the last expressed juice a special spindle or a pyenometer should be used.

The dilution at which Brix determinations should be made on syrups, massecuites, and molasses, has been a very controversial subject. This is a very important matter as it affects both the calculation of available sugar and the Brix balance.

Noel Deerr concluded from his investigations that all Brix determinations, in order to be comparable, should be made at equal concentration of non-sugar. In the case of final molasses this would require such extreme dilution, however, that the multiplied experimental error would be greater than the error which the method is trying to correct. As a compromise, the Hawaiian method, used also in other countries, prescribes dilution to approximately juice density.

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H. G. Hill,16 on the basis of experimental work with synthetic juices and molasses, contends that the rule enunciated by Deerr is not correct, and that while syrup should be diluted to juice density, final molasses should be diluted at a ratio of not less than one to one of water, and preferably an even higher ratio. But Noel Deerr has shown by an example that calculation of the avail­able sugar on the basis proposed by him gives the same value as calculation based on true purities.

If Hill's figures for synthetic juice and molasses are subjected to a similar analysis, the following results are found:

Juice: Dry substance 15.00; Brix 15.39: true purity 85.00; gravity purity 82.83. Molasses: Dry substance 80.00; true purity 40.00; Brix by dilution to 50 per cent. dry substance 86.03, corresponding gravity purity 37.20; Brix by dilution to 15 per cent. dry substance 87.81, corresponding gravity purity 36.48.

If the s-j-m formula is applied to the above sets of figures it is found that the available sucrose on the basis of the true purities of juice and molasses is 88.23 per cent. The same calculation with the use of gravity purities gives 87.72 per cent. when the Brix from dilution to 50 per cent. dry substance is used, and 88.09 per cent. when that from dilution to 15 per cent. dry substance is used. The latter figure is much closer to 88.23 per cent. available sucrose than the former. In order to arrive at 88.23 per cent. available sucrose from gravity purities, that of the molasses would have to be 36.20; this would be found if the molasses were diluted to about 1 per cent, dry substance, which fully accords with Deerr's postulate. Hill did not determine the Brix of the undiluted molasses, but it would be somewhere around 84; this would give the very low­available sucrose value of 87.24 per cent.

It is evident from these calculations that Noel Deerr is correct, and that Hill's reasoning is faulty. Noel Deerr's system of diluting to the approximate density of the mixed juice applies in all cases. The most practical way is to dilute a definite weight of product with an exact multiple of its weight of distilled water (the use of tap water may lead to serious error). The multiple must be chosen so that the diluted solution is of about juice density. The actual ratios will vary somewhat from place to place, depending principally on the character of the cane (low juice densities in subtropical countries) and on the amount of imbibition used. In Hawaii, for instance, the ratio for syrup dilution would generally be as 1 to 5 (1 plus 4), but in Java as 1 to 3 (1 plus 2), or 1 to 4 (1 plus 3). The dilution used in Java for final molasses, namely 1 to 10 (1 plus 9), is theoretically better than that to juice density, but it has the disadvantage that it requires the use of the pycnometer for the Brix determination. A dilution of 1 to 8 is about the limit if the Brix of final molasses is to be determined with the spindle. In practice, the possible error in the gravity purity of

60

final molasses, caused by dilution to juice density instead of diluting strictly to equal concentration of non-sugars, amounts to only about 0.2, which is less than the deviation possible by permissible errors in the Brix reading or polarization.

The reasoning developed for Brix determinations by spindle applies equally to Brix determinations with the refractometer.

The calculation of molasses weights from the volume and specific gravity is of course an entirely different matter. Here the density must be determined upon the original material, by weighing a definite volume, or if commercial contracts so specify, by double dilution and spindling.

If, as has been shown, available sugar must be calculated on the basis of gravity purities arrived at according to the directions given above, it naturally follows that balances should be calculated on the same basis.

Brix of Low Grade Sugars.—Here the method of diluting to approximate juice density is to be used also. But on high grade sugars the dry substance is to be determined because the possible error in the Brix determination may exceed the total moisture content of the sugar.

Brix in Bagasse.—A direct method for determining Brix in the water extract prepared for the polarization of bagasse has been worked out by Erlee.17 But the procedure is rather tedious, the error in the determination is multiplied by 10, and the method is not suitable for routine work. Until a simpler method is devised, the Brix of the bagasse must be calculated as shown in Chapter I I I .

Brix of Condensates from Vapour Lines.—This determination is necessary only for finding the pol in the condensate by Schmitz's method. If desired for this purpose, the Brix must be determined with special spindles or by pycnometer.

Brix of Milk of Lime.—This figure is not required to be reported. If it is desired, the Java method of weighing the milk of lime in a one-litre volumetric flask is recommended; determination with the spindle is not accurate because the lime has a tendency to settle out during the determination,

Suspended Solids. Suspended Solids in Mixed Juice.—Here it is necessary to

differentiate between coarse suspended matter which settles out by gravity in 15 to 20 minutes, and the more highly dispersed suspensoids which do not. In Brix determinations upon mill juices the former are allowed to settle before spindling and they do not affect the result. However, the settling matter does affect the weight of the juice, and theoretically the weight of the juice should be corrected for i t ; but in practice this is usually not done, and the Committee has recommended to report the gross weight of the juice (see p. 43).

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The suspended matter which does not settle out also has an effect on the Brix of the mill juices, causing an error of 0.5 to 1 in the purity. But a correction for this is not recommended by the Committee.

The quantity of settling suspended matter may be readily determined in mill juices, if desired, by repeated settling and decantation with water, or better by repeated centrifuging and decantation with water, followed by filtration through a tared dry filter paper or asbestos mat in a Gooch crucible, washing, drying, and weighing. Both methods give substantially the same results.

Suspended Solids in Final Molasses.—The simplest method is that used in Hawaii. Five grams of the molasses is diluted with distilled water to 500 ml. the solution filtered, and the residue dried and weighed. This determination is not made regularly in Hawaii, however, and as a rule an arbitrary correction is added to the Brix of the molasses actually found. The purity rise due to the correc­tion for suspended matter does not usually exceed 0.2.

The Hawaiian method probably does not give an exact measure of the suspended matter in the undiluted molasses. The added water may dissolve some of the material which is insoluble in the concentrated product, and on the other hand, certain colloids which are peptized by the concentrated sugar solution are flocculated by dilution with water, as has been shown by Peters and Phelps.18

Any number of different values may thus be obtained for suspended matter, depending on the dilution chosen. The error is largely avoided in the method used in Java, which is, however, rather complicated and unsuited for routine control. Two parts molasses are diluted with one part of water, the solution is centrifuged in a de Laval separator, and the solid residue is weighed net. Pol is determined in the residue, and the run-off is analysed for densimetric Brix, refractometer Brix, and pol. A correction, based on refracto­meter Brix of the solution before and after centrifuging is applied, and the amount of dry suspended matter is calculated from the data obtained.19.

The committee has decided to omit the determination of suspended matter in final molasses.

Foam Correction when Mixed Juice is measured.—The deter­mination of this correction has been described in Chapter V, page 43.

Pol. The methods for determining direct polarization are so well

standardized that they require no detailed discussion. But the standardization of the normal solution requires some comments.

In the countries which employ instruments with a normal weight of 26 grams, most of the older saccharimeters are calibrated according to the Herzfeld-Schonrock scale (100° = 34.657 circular

62

degrees). In 1932 the International Commission for Uniform Methods of Sugar Analysis adopted the hundred point found by Bates and Jackson (100° = 34.620 circular degrees). This new scale is known as the "International Sugar Scale", and the readings on this scale as "International Sugar Degrees". This scale is based on a normal weight of 26.000 grams, weighed in air with brass weights, dissolved to 100 ml. at 20° C, and read at 20° C. in a tube of 200 mm. length upon a saccharimeter calibrated at 20° C. One hundred International Sugar Degrees equal 99.9 degrees on the Herzfeld-Schonrock scale. If instruments graduated according to the old scale are used, the normal weight must therefore be taken as 26.026 grams, or, if the 26.000 gram normal weight is used with such instruments, the readings must be divided by 0.999.

The International Commission, at its 1932 meeting, did not act on the question of the volume of the precipitate produced when lead subacetate solution is used for clarification. The error caused by this precipitate is opposite to that in the Herzfeld-Schonrock scale. In 1936 the International Commission decided that, when a change is made from the old scale to the new scale, Horne's dry subacetate is to be used for clarification, in order to eliminate both errors at the same time. This Committee had previously recommended dry lead subacetate for clarification, and it follows that under this condition the new scale or the new normal weight are to be used henceforth. Normal weight pieces of 26.026 and 13.013 grams are available on the market, in hexagonal form, to prevent confusion.

The correct normal weight for instruments graduated according to the French scale (100 degrees = 21.667 circular degrees) is 16.269 grams, and that for the so-called 20-gram sugar scale (bi-decimal, 100 degrees = 26.600 circular degrees) is 19.973 grams. With these corrected normal weights, instruments of these two types will give the same reading as the normal weight of 26.000 grams on the International Scale, or 26.026 grams on the Herzfeld-Schonrock scale. The old normal weight of 26.048 grams, dissolved to 100 Mohr's cubic centimeters, is to be discarded absolutely. The old Schmitz tables, which were calculated on this basis, for clarification with either lead solution or dry lead, must be replaced by corrected tables.

Since all modern saccharimeters are standardized at 20° C., all pol determinations should logically be made at this temperature, particularly because pol figures, in the presence of undetermined quantities of levulose and other optically active constituents, cannot be corrected for temperature. But it is obviously impossible in practice always to polarize at 20° C. As has been pointed out in Chapter IV, p. 29, this very circumstance adds to the unreliability of all factory reports based on pol. Sucrose determinations, on the other hand, are corrected for variations in temperature. As long as pol determinations cannot be made at exactly 20° C, it is best to make them at average room temperature. Although this prevents

63

direct comparisons of pol figures obtained in different countries, it is the best that can be done until sucrose determinations are made obligatory everywhere.

It has sometimes been proposed to calibrate saccharimeters to be used in the tropics at a higher temperature, say, 27.5° C, but such instruments would give correct readings only upon solutions of pure sucrose; the error caused by the presence of levulose and other optically active impurities would still remain, and the results could not be compared with those obtained upon instruments calibrated at 20° C.

Clarification for Pol Determinations.—Lead subacetate solution has been widely used for this purpose in the past, but the precipitate reduces the volume of the solution and causes a corresponding plus error. This error can be readily avoided by the use of the proper amount of Horne's dry subacetate of lead, added after the solution has been made to the mark. Dry lead has the further advantage that weighing of the product, or exact measuring of its solution becomes unnecessary if the Schmitz-Horne method is used. Purity determination on the solutions diluted as specified under Brix determination thus becomes a very simple and rapid operation. Since lead subacetate is also a good preservative for juices the use of the dry salt makes it very easy to composite samples. For all these reasons the Committee has decided to adopt Home's dry lead for clarification prior to polarization. One gram of the dry salt is equivalent to about 3 ml. of the solution of 1.25 specific gravity. Instead of the Schmitz-Horne method, the normal weight method with dry lead clarification may of course be used if pre­ferred, but as a rule this presents no particular advantage.

Mauritius specifies the use of dry powdered neutral lead acetate for clarification because of the effect of basic lead acetate on the reducing sugars. The practical objection to neutral lead acetate is that frequently it does not decolorize the solution sufficiently to be read accurately in a 200 mm. tube.

Pol in Bagasse.—All the methods in general use for this deter­mination are based on the same general principle, i.e., extraction of the bagasse with water at or near the boiling point, followed by clarification and polarization of the extract. But there are many differences in details, and these may have a decided effect on the results. In many countries only 100 grams of bagasse or even less is used as a sample. Such small samples cannot be considered to be truly representative, especially when the bagasse is not finely divided. For this reason the Committee recommends much larger samples, at least 500, and preferably 1,000 grams.

In some of the methods the water is allowed partially to evaporate during the digestion, and this makes it necessary to weigh the bagasse plus liquid at the end of the digestion. Calcula­tions may be greatly simplified by digesting under reflux. The

64

quantities of bagasse and water may then be chosen so that the saccharimeter reading gives the sugar in bagasse without reference to the fibre content (which is actually unknown because the pol figure is used for its calculation), but on the basis of the water content of the bagasse which is determined any way in a separate sample.

Some methods prescribe the use of pure water for the extrac­tion, while others specify the addition of small quantities of alkali to prevent the hydrolysis of sucrose or pentosans. Hadley and Hayes20 have reported that boiling water, without the addition of alkali, extracts from bagasse a dextrorotatory substance which has been identified as xylose. Although this finding has not been confirmed by similar investigations in Java and Cuba, alkali should nevertheless be added to prevent the hydrolysis of sucrose. Some pentosan may be extracted by the weak alkali, but this does not interfere because it is precipitated by the lead subacetate used for the clarification of the extract.

Another important point to be considered in this connection is the ratio of water to bagasse. Behne10 has found that this ratio has a decided effect on the result, no matter whether the bagasse is actually boiled with water alone, or heated in a water bath with alkalized water. When the ratio is as five to one, lower results are obtained by either of these two procedures than when the ratio is as ten to one.

The time of boiling prescribed in the different methods varies generally from one half to one hour. The old discussion about the temperature and time of heating will probably go on indefinitely. It stands to reason that if the temperature is reduced the time of heating must be extended. Dymond has proposed to extract at 50° C. for two and a half hours. Unless it can be proved beyond doubt that boiling is radically wrong it should be retained in order to complete the analysis in a shorter time. It is of course better to extract a little longer than not long enough.

For the reasons outlined the Committee recommends that at least 500 grams, and preferably 1,000 grams of bagasse be gently boiled under reflux with ten times its quantity of water for one hour in a suitable apparatus, e.g., those described by Khainovsky22

or Deerr.22 A little sodium carbonate (1 g. of Na2CO3 per litre) or lime water should be added to the water in order to prevent inversion, unless ammonia has been used to preserve the bagasse. The extract is clarified with dry lead, filtered, and the filtrate polarized in a long tube (400 mm.). The water is corrected for the water in the bagasse, and the pol in the bagasse is calculated from the polarization of t he extract. If the ratio of water to bagasse was as ten to one, the per cent, water m the bagasse = w, and the polarization in the 400-mm. tube = P, then

Sugar per cent. bagasse =26 P x (1000 +w) 20000

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Recent investigations, as for instance by Schmidt, Wiggins and Yearwood,37 indicate that, as an alternative to boiling, complete mixture between the soluble constituents of the bagasse and the added water may be promoted by disintegration of the bagasse in the presence of the water. This may be achieved in a high speed mixing unit of which the "Waring Blender" is probably the classical type. Various equivalent devices are available commercially, some with overdriven, some with underdriven impellors.

It is claimed that not less than 15 parts of water must be used per part of bagasse, and in these proportions the regular size of blender will accommodate less than 50 g. of bagasse. The dis­integration is reported to occupy 20 minutes.

There is thus a distinct saving in time when the blender is used, and, as larger and more robust mixers become available, the new principle is likely to be widely adopted, particularly for inter­mediate bagasses. The formula to be used for calculation of sucrose per cent. bagasse is, of course, as above with modification of the numerical values to suit the ratio of bagasse to water.

Pol in Filter Cake.—The Committee recommends the following method which is quite generally used: Triturate 25 grams (normal weight, corrected for volume of insoluble) of the cake with hot water in a mortar to a smooth paste, wash with hot water into a 100-ml. flask having a wide neck above the mark, cool, complete the volume, add 1 to 2 g. of Horne's dry lead, shake, filter, and polarize. The reading in a 200-mm. tube gives pol in filter cake. Some chemists prefer to use 50 g. of filter cake, made up to 200 ml. or, 25.5 g. of the cake may be made up to a total volume of 200 ml., and the reading taken in a 400 mm. tube. It is not necessary to neutralize the solution with acetic acid before filtering.

Pol in Carbonatation Cake.—The Java method is recommended: Fifty grams of the cake is transferred to a porcelain mortar with water, 15 g. of ammonium nitrate crystals is added, followed by more water, and when a homogeneous mass is obtained it is washed into a 200-ml. flask. The analysis is completed as described under filter cake.

Pol. of Sugars.—The International Commission for Uniform Methods of Sugar Analysis specifies that raw sugars be polarized at 20° C. because the temperature correction varies with the per­centage of levulose and other impurities. If a temperature correc­tion were applied in the case of sugars it should logically be applied to all other factory products. This is impracticable, as has been pointed out before, and for this reason the pol determinations should all be made at room temperature which should fluctuate as little as possible.

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In commercial transactions, however, the sugars should be polarized at 20° C, as prescribed by the International Commission. If this is not possible, the temperature correction formula given by Browne may be used without serious error:

P20 = Pt+ 0.0015 (Pt—80) (t—20)

where t is the temperature, and P the direct polarization.

In some countries, as in Natal, local temperature corrections are used, but they are not generally applicable.

Qualitative Test for Sugar. Alpha-naphthol is quite generally used for this purpose,

although this reagent is considered by some chemists to be too sensitive, preference being given to the ammonium molybdate test. The alpha-naphthol test may be carried out in many different ways, but the method used in Java is recommended. This test is not based on the formation of a ring between two layers of liquid, which is largely influenced by more or less accidental mixing at the inter­face, but on an even coloration of the liquid as a whole. The water sample to be tested is poured into a test tube, poured out again, and only the film of water adhering to the test tube is used for the test. This removes the objection of too great sensitivity. Lysol and cresol solutions have the advantage that they do not deteriorate on standing, while those of alpha-naphthol must always be prepared fresh. The choice of the reagent and the details of making the test may well be left to individual countries.

Sucrose. Sucrose determinations are not required for running control,

but only for the technical accounting of recoveries and losses. They may therefore be made upon properly composited and pre­served samples, and more time and care may thus be devoted to them. In the case of bagasse and filter cake the sucrose is by common consent considered to be equal to pol. But according to the recommendations offered in Chapter IV, sucrose must be deter­mined in mixed (or clarified) juice, syrup, final molasses, and sugar.

The subject of sucrose determination by double polarization has been studied intensively by the Association of Official Agri­cultural Chemists,23 and it has been found that, no matter what method of inversion is used, certain rules, which are often neglected, must be followed. The principal rules are:

1. The lead salts and deleading agents used for clarification should be added in exactly equal quantities to the solution for the direct reading and to that to be inverted. The best way to accomplish this is to clarify and delead the entire original solution, and then to employ one portion of the final filtrate for the direct reading, and another portion for the inversion. The pipettes used

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to measure the solutions into the flasks should be calibrated with sugar solution of the density employed, and not of distilled water, because the differences in viscosity are sufficient to cause important errors.

2. The solution for the direct reading and that to be inverted must have the same dry substance concentration. The old Herzfeld procedure of using unit concentration for the first, and half con­centration for the second, does not give correct results in the presence of non-sucrose.

3. The Clerget constant must be based on the dry substance concentration and not on the partial sucrose concentration. The tables found in the text-books usually give factors for varying sucrose concentration, or for the difference between direct and invert polarization, or, what is even worse, for the negative reading only. The first of these tables may be used if the basic factors are correct and if the dry substance concentration is substituted for the sucrose concentration. As the Brix is always determined for the same product, this may be used without appreciable error to calculate the dry substance concentration for the particular dilution employed. The other two types of tables do not give correct factors for impure products.

The concentration coefficient for the methods using hydro­chloric acid as the hydrolysing agent was, for a long time, accepted as being 0.0676 per gram of dry substance in 100 ml. solution. Jackson and Macdonald showed that this value is too low and derived a new coefficient of 0.0794. This value has been accepted by the International Commission for Uniform Methods of Sugar Analysis. Various concentration coefficients have been proposed for the invertase method, but the value now accepted by the I.C.U.M.S.A. is 0.0833. Various other methods of determination of sucrose, involving different concentration coefficients are in use, but as these methods are not recommended by the Committee, the constants involved have no place in this publication.

The temperature coefficient generally accepted is —0.5 for the invert sugar, and —0.03 for the sucrose, making the combined coefficient —0.53, and this is the value adopted in the official formulae of the I.C.U.M.S.A. For routine factory control the value 0.5 may be adopted, but the routine chemist usually has access to a table of temperature corrections and in the compilation of such a table it is just as easy to adopt the preferred value 0.53 as the approximation 0.5.

The investigations of the Association of Official Agricultural . Chemists have shown that the invertase method is the only one that can be depended upon to give correct sucrose values for cane products irrespective of the presence of levulose, reversion products, and amino compounds, provided that the solution used for the direct reading and the inverted solution have approximately the

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same pH. One objection to the method prescribed by that associa­tion is the use of sodium carbonate for deleading. This not only has a tendency to destroy invert sugar, but often darkens the colour of the solution to such an extent that it cannot be read accurately in the saccharimeter. These objections can be readily overcome by using ammonium dihydrogen phosphate as the delead­ing agent. The slight acid reaction of this salt is not sufficient to cause inversion in the solution for the direct reading within a reasonable time.

The chief objection to the general use of invertase has been that it was not available commercially at a reasonable price. Invertase may be prepared by Reynold's ultrafiltration method, but the average factory laboratory usually prefers to purchase its reagents. Invertase made by the Willstatter method of absorption and elution usually does not keep as well as that purified by ultra­filtration, and it sometimes gives erratic results. The yeast gums retained in preparations made by ultrafiltration have a stabilizing effect. Nowadays reliable preparations of invertase for analytical work are available commercially, but to most factories the price appears too high and the technique of its use not familiar enough for invertase to be adopted for routine use.

Until invertase is generally adopted for routine purposes, a choice has to be made among the various methods using acid for hydrolysis. The best known of these are the Jackson and Gillis methods with hydrochloric acid, and Deerr's method of employing sulphuric acid as the inverting agent. Jackson and Gillis method No. 1, which in principle is the same as the Herzfeld-Schrefeld method, and Jackson and Gillis method No. III are both ruled out because they are admittedly not applicable when invert sugar is present in the original product. Method No. II gives too high results when the material contains reversion products as is usually the case with cane products, except juices. This applies also to method No. IV, but in this case the high result is partly com­pensated by the effect of amino compounds which tend to lower it. Hence the sucrose found by Jackson and Gillis method No. IV comes closest to that obtained by the invertase method, although it averages somewhat higher. It follows that, of the Jackson and Gillis methods, No. IV is the best for cane products.

Deerr's double polarization method with sulphuric acid as the hydrolysing agent is similar in principle to Jackson and Gillis method No. I I , and should give approximately the same results provided that the inversion is carried out at a temperature not above 60° C. In Deerr's method a correction is applied for the volume of the precipitates obtained in clarification, but it is doubtful whether the volumes are the same in the case of impure products as in that of pure sucrose. In the Jackson and Gillis methods there is no error from the lead precipitate if the correct amount of dry lead is used. The precipitates obtained in Deerr's method have

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been found to Have a tendency to run through the filter which makes it necessary to pour back several times, thus increasing evaporation; besides, the clarified solution often becomes turbid on standing. These difficulties have not been encountered in India, but nevertheless the method has found little favour elsewhere.

Taking all the different factors into consideration, the Com­mittee has decided to adopt Jackson and Gillis method No. IV for sucrose determinations. The International Commission for Uniform Methods of Sugar Analysis has taken the same action, for the analysis of cane molasses. A complete description of the method is given in Bur. Standards Sci. Paper No. 375 (1920), and also in various handbooks and text-books on factory control. The above recommendation has been made with the proviso that this method is to be superseded as soon as possible by the invertase method. The most practical inversion procedure is that according to Walker. The solution to be inverted is heated to 65° C, then the acid is added, the flask rotated to mix the solution, and allowed to stand at room temperature for 15 to 30 minutes. The chemist must satisfy himself that inversion is complete under local conditions. In the tropics standing for 30 minutes is usually quite sufficient, but slight modifications are necessary in the temperate zone or during the winter in subtropical countries. If there is any doubt about the completeness of inversion it is best to acidify first and then to heat to 60° C. for nine to ten minutes, depending on the purity of the product.

The Clerget divisors accepted by the I.C.U.M.S.A. are as follows:

Inversion with Invertase

Divisor = 132.1—0.0833 (13 — m) - 0 . 5 3 (t — 20).

Inversion with hydrochloric acid at 60° C. (U.S. Customs Method)

Divisor = 132.56—0.0794 (13— m)— 0.53 (t—20). The I.C.U.M.S.A. has not specified a formula for use with

the Walker method of inversion, but the commonly accepted formula is

Divisor = 132.64-0.0794 (13— m) — 0.53 (t —20). Where m is the grams of solids per 100 ml. of the solution

as polarized and t is the temperature at which the read­ings are taken, in degrees C.

For clarification previous to sucrose determinations Horne's dry subacetate of lead is recommended, for reasons already fully explained (see p. 64). In Java Herle's basic nitrate reagent is preferred because it gives a much lighter solution than lead sub­acetate. This advantage is admitted, but the error due to the

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volume of the precipitate is a serious objection. If a dry basic lead nitrate having the same clarifying effect as the solution could be prepared, this objection would disappear.

In Jackson and Gillis method No. IV it is not usually necessary to delead the solution because the hydrochloric acid and sodium chloride are sufficient for this purpose. If a large excess of lead has inadvertently been used it may be removed by adding dry potassium or sodium oxalate and filtering again before taking portions of the final solution for the direct reading and for inversion. If the inverted solution is too dark to read, addition of a little zinc dust and refiltering is helpful and permissible. Small amounts of dry sodium sulphite may also be employed for the same purpose, but charcoals should not be used unless it is definitely known that they do not affect the polarization. If the solutions cannot be read even after zinc dust has been used it is best to increase the intensity of the light source or to increase the half shadow angle where this is possible.

There is little doubt that for certain analyses the optical methods of determination of sucrose will be superseded by the chemical methods involving the determination of reducing sugars before and after inversion. This principle serves to best advantage in the analysis of materials containing only a moderate proportion of sucrose in association with an appreciable content of reducing sugars—as, for instance, final molasses. In such cases the optical methods yield only moderate satisfaction and are unlikely to survive.

Reducing Sugars . Of the various available methods, that of Lane and Eynon

has been thoroughly tested and has become so firmly established in a number of cane countries that the Committee recommends it for routine factory work. The methods requiring filtration of the cuprous oxide, while very exact if the copper is determined gravi­metrically or volumetrically in the precipitate or filtrate, are time consuming, and the iodometric methods are expensive. There can be no objection to the use of these methods, but the Lane and Eynon method is considered to be the most practical for quick routine determinations, upon both juices and molasses. The work can be further expedited if the preliminary titration is made upon an unclarified solution of juice or molasses, diluted approximately to the proper concentration. The exact dilution to be used for the final titration, after clarification, can thus be ascertained quickly, and one further test will give the desired result.

In the analysis of dark coloured products by the Lane and Eynon method difficulty is sometimes experienced in determining the exact end point when methylene blue is employed as the indicator. This difficulty may be overcome by using an electro­metric end point device such as that described by Saint and

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Follett-Smith,25 and further improved by Von Stieglitz and Home.26

The end point may also be determined by potentiometric titration using a noble metal electrode according to Cameron.27

Main's pot method,28 which is a modification of that of Lane and Eynon, is capable of high precision but it requires considerable time unless the invert sugar content is known within narrow limits. A number of tubes must be prepared to find one pair which gives the desired result. If the proper range or the proper intervals have not been chanced upon the first time, another series of tubes must be made up. In a given factory where the reducing sugar content is approximately known, the manipulations may be reduced, but not to the extent possible with the Lane and Eynon method. Main's procedure may, however, serve as a valuable check in doubtful cases.

Basic lead acetate should not be used to clarify solutions for the determination of reducing sugars because it is known partly to precipitate them. Lime salts must, however, be removed in all cases, and this is best accomplished by means of dry potassium or sodium oxalate, if necessary with the addition of some kieselguhr as a filter aid. To remove reducing substances other than sugars a minimum quantity of neutral lead acetate may be used, and any excess removed by means of dry oxalate, or better with a solution containing 30 g. of potassium oxalate and 70 g. of disodium phosphate per litre. Any large excess of neutral lead acetate must be avoided as it is apt to precipitate small quantities of reducing sugars.

The Lane and Eynon method is applicable also to raw sugars, no clarification being required in this case, except filtration with a little kieselguhr. If the invert sugar content is less than 0.8 per cent. a known quantity of pure invert sugar solution must be added to the sample, and a correction applied for it.

For the analysis of sugars containing only very small quantities of reducing sugars, such as refined and high grade consumption sugars, Main's pot method is particularly suited because, although it is laborious, its precision is very high. Kraisy's titration method29

gives practically the same results as Main's pot method upon refined sugars, and it may be used as an alternate procedure. De Whalley's colorimetric method30 for refined sugars is more rapid than Main's method, and its results agree well with those of the pot method if the standards have been correctly calibrated. A further study of De Whalley's method is recommended.

In the case of high grade consumption sugars the method of Luff,31 official in Java, may also be employed.

Ash. This has been defined by the Committee as "the residue

remaining after burning off all organic matter". This implies the method of determination, namely, direct incineration. But there

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is a question whether the ash, as thus defined and determined, is really the material whose quantity we wish to ascertain, because it does not exist in sugar products in that form. In Hawaii the idea prevails that only the inorganic salts or ions present in the product should be considered, and from this point of view plain incineration gives too high results as the ash obtained contains the carbon dioxide formed from the organic acids. However, even if the Hawaiian view were generally accepted, it must be considered that the plus error is partly compensated for by a minus error caused by the volatilization of variable and indeterminate amounts of chlorine, as observed by Browne and Gamble,32 and the possible loss of sulphur and phosphorus also. If the percentage loss of chlorine were always the same this would not matter so much, but it depends on the alkalinity of the ash and on the conditions of incineration. If the sulphated ash, obtained directly, checks with that prepared by treating the carbonated ash with sulphuric acid and incinerating, this is considered in Hawaii as proof that chlorine has not been volatilized in direct incineration. But if they do not check, nothing has been proved. The idea that the carbonated ash, including or excluding the carbonates present, is an exact measure of the mineral constituents in the product itself, is erroneous and only sanctioned by tradition.

It has been shown that the sulphated ash bears no constant relation to the carbonate ash, but this has no real significance as long as the carbonate ash itself cannot serve as a standard. The results by either method are purely empirical, but in the case of the sulphated ash we at least have the assurance that there are present quantitatively the fixed bases, the silica and phosphorus pentoxide, and the equivalent of the volatile inorganic and the organic acids, in the form of combined sulphur trioxide.

In contradistinction to the view held in Hawaii, there is the opinion expressed by Lunden33 that what we really wish to deter­mine is not the ash, but the salts present in the product. He found that the sulphated ash presents a correct relative measure of the salts and that the sulphated ash figures for different products are mutually comparable. If this view is correct the entire question of a correction factor to convert sulphated ash into carbonate ash is completely eliminated. The Java Sugar Experiment Station has accepted this standpoint and reports sulphated ash without any deduction whatever; the Association of Official Agricultural Chemists has also decided to report sulphated ash without any correction. It is true that these figures are very much higher than the carbonate ash, but even then they are lower than the true salt content because the equivalent weight of the organic anions in cane products is higher than that of the sulphate ion (that of aconitic acid, which is the principal organic acid in sugar cane, is 57 if it reacts as a tribasic acid, and even higher if it reacts as a dibasic or monobasic acid).

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Accepting Lunden's view, the Committee has decided that the sulphated ash be determined and reported as such, without any correction, either as "Sulphated Ash", or as "Salts", since the sulphated ash is a correct relative measure of the latter. This procedure has the further advantage that the determinations can be made more quickly and easily, and that the careful temperature regulation necessary for carbonate ash is not required.*

The acceptance of Lunden's conclusion that the salts are the important thing to consider, and not the ash, also opens the way for replacing chemical ash determinations by measurements of the electrical conductance which is correlated with the sulphated ash. Methods of "ash" determinations based on this principle are already widely used in the beet sugar industry in Europe, and are official in Czechoslovakia and in Germany for determining the ash in raw beet sugars. The International Commission for Uniform Methods of Sugar Analysis also favours this method for raw beet sugars, but has made no ruling as yet on cane products. The latter subject has been investigated principally in the United States and in Java, and has been given attention in other cane countries also. The information available at the present time is not sufficient to put forward a definite recommendation, but the rapidity and ease of execution of the method offer such obvious advantages that it may be possible to adopt it in some form later on. It may then be advisable to abandon all comparisons with the chemical ash and to apply, by common consent, some empirical factor to the result of the conductance determination, and to report as "Salts by conductivity".

Where a deduction of 10 per cent. from the sulphated ash of raw sugars is made for the purposes of commercial transactions the practice must presumably be adhered to. However efforts should be made to have the commercial formulae amended to conform to the international method of reporting ash.

Titrated Acidity or Alkalinity. Little need be said about these since they are not to be reported

but used only for the information of individual factories. The titration of acid juices is carried out with N/10 or better N/28 alkali, usually sodium hydroxide, and with phenolphthalein as indicator. The acidity should be expressed as milligrams calcium oxide necessary to neutralize one litre of juice, and not as milliliters of standard alkali for some unit volume of juice. The Hawaiian practice of saying "per cent." lime, when grams CaO per 100 millilitres of juice is meant, is misleading.

*Since this decision was formulated by the Committee the I.C.U.M.S. A. has also agreed that sulphated ash shall be reported as measured, without any deduction. However, the I.C.U.M.S.A. recommended tha t the term "sulphated ash" be replaced by "gravimetric ash". The Committee will doubtless consider whether the new term should be adopted, but the present term has the advantages of being both familiar and descriptive.

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Alkaline juices are ti trated with standard acid, and the alkalinity is expressed also as milligrams CaO per litre of juice. The acidity of juices or syrups due to sulphur dioxide is to be expressed as milligrams SO2 per litre. Hydrogen Ion Concentration.

For the running control of the factory the colorimetric method is quite generally used. Either the comparator procedure with test tubes, or spot plates with colour charts may be employed. The last named method has been highly developed in Hawaii and in Java. But even with carefully prepared colour charts the vary­ing colour and turbidity of the products themselves cause many practical difficulties, as the procedure is purely subjective. The great dilution necessary for some products has a decided effect in shifting the pH, and average corrections do not always apply to individual samples. During the past few years simple electrometric apparatus, utilizing either the quinhydrone or the glass electrode, have been placed on the market, and their use is recommended in preference to indicators. The quinhydrone electrode is not accurate above about pH 8.5, and it is subject to error when oxidising or reducing substances are present in the solution. The glass electrode is preferable to the quinhydrone electrode because it is not affected by such substances. Its useful range is up to about pH 9.5, which is ample for the usual factory products. Special electrodes are on the market which may be employed in solutions with a pH as high as 12. The glass electrode is par­ticularly useful for unbuffered solutions, as those of refined sugars. Special glass electrodes that can be used at high temperatures are now available so that the pH of hot juices can be determined without difficulty.

Available Calcium Oxide in Lime. The method prescribed in Hawaii5 is recommended. It reads

as follows: "Weigh quickly 5 grams of a finely ground sample of lime, transfer to a 250-ml. flask with from 75 to 90 ml. of freshly boiled distilled water. Boil gently for 3 minutes, then cool to room temperature. Add 40 to 45 grams of commercial white sugar completely dissolved in 40 ml. of freshly boiled distilled water; shake vigorously for 30 minutes with a rotating motion of the flask, keeping the lime in suspension; fill to mark, mix and filter, discard­ing first runnings. Pipette off 25 ml. of filtrate and t i t rate with standard N/2.S sulphuric acid, using phenolphthalein as an indicator. The number of millilitres required, multiplied by 2, equals the percentage of available calcium oxide in the lime".

Subsidiary Methods. The constituents which follow are of no importance for inter­

national comparisons of control data, but since the Committee has discussed and acted upon methods for their determination, the recommended procedures are briefly outlined.

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Sulphur Dioxide in Juices and Syrups.—The routine method for this determination is titration against standard iodine solution in the presence of hydrochloric or sulphuric acid, with starch as indicator. The result is expressed as milligrams sulphur dioxide per litre.

Sulphur Dioxide in Sugars.—The Natal methods34 are recom­mended. For rapid routine tests titration with iodine may be used. Any oxysulfonates present are first broken up by adding excess alkali. After standing for 15 minutes the solution is again acidified with sulphuric acid, and an excess of standard iodine solution is run in immediately. After another 15 minutes the excess iodine is titrated back with standard thiosulphate. The result is expressed as milligrams sulphur dioxide per kilogram of sugar.

If more exact results are desired, and particularly if the sulphur dioxide content is near the maximum legal limit, the Monier-Williams distillation method35 should be used. The sugar solution is acidified with hydrochloric acid, the evolved sulphur dioxide is distilled in a current of carbon dioxide into hydrogen peroxide, and the sulphuric acid formed is titrated with standard alkali.

Calcium Ion in Juices, Syrups, and Molasses.—This may be determined quickly with standard soap solution by titration,19 but the results are only approximate. For more exact determinations precipitation as oxalate and titration with permanganate is recom­mended. The juice or solution is acidified with acetic acid, purified kieselguhr is added, and the mixture is boiled and filtered. The filtrate is again brought to boiling, the calcium precipitated with an excess of hot ammonium oxalate solution and the analysis completed as usual. The results should be checked occasionally by ashing the juice or other product and determining the calcium in the ash. It must be considered that the latter result includes the calcium present in the suspended matter unless this is removed by filtration previous to the ashing.

Phosphate Ion in Juices.—For the determination of phosphates the cceruleo-molybdate method is almost universally used. This is a colorimetric method, based on the reduction of phosphomolybdic acid by stannous chloride. Details of the method are readily avail­able from reference books36. Some important points to be noted regarding the method are (1) the stannous chloride solution will oxidise if left in contact with air, but may be protected by a layer of paraffin oil; (2) the standard phosphate solution of the strength used in the test is susceptible to decomposition by micro-organisms; the stock solution should be made ten times the working concentra­tion; (3) the colour produced in the presence of sulphuric acid is pure, but commences to fade very soon after its formation; when a photo-electric colorimeter is available it is preferable to substitute

76

hydrochloric acid for sulphuric acid—the presence of a yellow component in the colour is unimportant if a red filter is used, and the colour is more permanent.

Carbon Dioxide in Lime Kiln Gas.—This is best controlled by means of approved and tested automatic recorders; the readings should be checked occasionally by direct determination with the Stammer or Orsat apparatus.

Sulphur Dioxide in Sulphur Oven Gas.—The Reich-Lunge method, as practised in Java,19 is recommended. This measures the volume of gas necessary to reduce 10 ml. of 0.1 N iodine solution; from this figure the percentage of sulphur dioxide in the gas is computed.

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CHAPTER VIII

Recapitulation of Factory Data recommended as a Basis for Report Forms

General. Name of Producing Country and Subdivision (State, Province, etc.). Name and Address of Factory. Period Covered by Report, from (date), 19 to (date), 19........ Rated Capacity of Factory, in Metric Tons Cane per Hour Grinding

Time (if desired, may be given also in customary units). Brief Description of Milling Plant (number, type, dimensions, etc.,

of knives, shredders, and milling units; see p. 23. Brief Description of Boiling House Equipment (juice heaters,

settling equipment, filters, evaporators, pans, crystallizers, centrifugals, etc., with capacities; see p. 39.

Indicate whether Milling Control is carried out according to Scheme A or Scheme B (see p. 25); if neither of these schemes is used give a brief description of scheme used.

Cane. Total Weight of Cane Ground, in Metric Tons; see p. 42. Total Weight of Cane Ground, Customary Units; see p. 41. Sucrose per cent. Cane; see p. 26. Pol per cent. Cane; see p. 26. Fibre per cent. Cane, Scheme B, if directly determined; see p. 25. or Fibre per cent. Cane, Scheme A, if calculated; see p. 25.

Imbibition. Weight of Imbibition Water, per cent. Cane,

Determined directly; see pp. 17, 25, 44 or Calculated from Volume; see p. 44. or Calculated from Fibre per cent. Cane; see p. 25.

Dilution per cent. Absolute Juice Extracted; see p. 26.

Bagasse . Weight of Bagasse, per cent. Cane,

Weighed directly; see p. 17. or Calculated by Scheme A; see p. 25. or Calculated by Scheme B; see p. 25.

Moisture (i.e., 100-Dry Substance) per cent. Bagasse; see p. 58.

78

Brix per cent. Bagasse, Determined directly; see p. 61. or Calculated; see p. 24.

Sucrose = Pol per cent. Bagasse; see p. 64. Fibre per cent. Bagasse; see p. 25.

Primary Juice. Brix per cent. Primary Juice; see p. 22.

Last Expressed Juice. Brix per cent. Last Expressed Juice; see pp. 24, 59. Pol per cent. Last Expressed Juice; see p. 24.

Mixed Juice.

Weight of Mixed Juice (if control starts with Mixed Juice), reported as per cent. Cane,

Gross Weight; see pp. 17, 24, 43. or Net Weight; see pp. 17, 43.

Brix per cent. Mixed Juice; see pp. 24, 59. Sucrose per cent. Mixed Juice; see pp. 24, 67. Pol per cent. Mixed Juice; see pp. 24, 62. Purity (Sucrose/Brix) of Mixed Juice; see pp. 25, 31. Purity (Pol/Brix) of Mixed Juice; see pp. 25, 31. Reducing Sugars as Invert Sugar, per cent. Mixed Juice;

see pp. 30, 71. Ash (Sulphated without deduction) per cent. Mixed Juice;

see pp. 30, 72. Lime Used.

Available Lime Used per thousand Cane (kilograms per metric ton); see pp. 29, 45, 75.

Hot Limed Juice. pH of Hot Limed Juice; see pp. 30, 75.

Clarified Juice.

pH of Clarified Juice; see pp. 30, 75. If control starts with Clarified Juice, report same figures as for

Mixed Juice (see above).

Filter Cake.

Weight of Filter Cake, per cent. Cane, Determined directly; see pp. 28, 45. or Calculated; see p. 45.

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Dry substance per cent. Filter Cake; see pp. 29, 58. Sucrose = Pol per cent. Filter Cake; see pp. 29, 66. Purity of Filter Cake; see p. 31. If the Syrup is filtered, report the same figures for the Filter Cake

obtained from it.

Syrup. Brix per cent. Syrup; see pp. 29, 59. Purity (Pol/Brix) of Syrup; see p. 29. pH of Syrup; see pp. 30, 75.

Massecuites . To be reported separately for each type of Massecuite: Hectolitres Massecuite per 10 Metric Tons of E.S.G.; see p. 28. Brix per cent. Massecuite; see pp. 29, 59. Purity (Pol/Brix) of Massecuite; see p. 31.

Intermediate Molasses . To be reported separately for each type of Intermediate Molasses: Brix per cent. Molasses; see pp. 29, 59. Purity (Pol/Brix) of Molasses; see p. 31.

Final Molasses . Weight of Final Molasses, per cent. Cane,

Determined directly; see pp. 28, 46. or Calculated from measurements; see pp. 28, 46.

Brix per cent. Molasses; see pp. 29, 59. Sucrose per cent. Molasses; sec pp. 29, 67. Pol per cent. Molasses; see pp. 29, 62. Purity (Sucrose/Brix) of Molasses. Purity (Pol/Brix) of Molasses. Reducing Sugars as Invert Sugar, per cent. Molasses; see p. 30, 71. Ash (Sulphated without deduction) per cent. Molasses; see p. 30, 72. R.S.-Ash Ratio of Molasses; see pp. 12, 31. Ash-Non-sucrose Ratio of Molasses; see pp. 12, 31. Ash-Non-pol Ratio of Molasses; see pp. 12, 31.

Sugars . To be reported separately for each grade of sugar, not returned to

process: Weight of Sugar, per cent. Cane; see pp. 28, 46.

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Moisture (i.e., 100—Dry Substance) per cent. Sugar (high grades); see pp. 29, 58.

Brix per cent. Sugar (low grades); see pp. 29, 61. Sucrose per cent. Sugar; see pp. 29, 67. Pol per cent. Sugar; see pp. 29, 67. Reducing Sugars as Invert Sugar, per cent. Sugar (Optional);

see pp. 30, 71 . Ash (Sulphated without deduction) per cent. Sugar (Optional);

see pp. 30, 73.

Sugar Balance, per cent. Sucrose in Cane. Sucrose in Sugars; see pp. 29, 67. Sucrose in Bagasse; see pp. 27, 64. Sucrose in Filter Cake ; see pp. 29, 66 Sucrose in Molasses; see pp. 29, 67. Sucrose, Undetermined

100.00

Pol Balance, per cent. Pol in Cane.

Pol in Sugars, see pp. 29, 67. Pol in Bagasse; see pp. 27, 64. Pol in Filter Cake; see pp. 29, 66. Pol in Molasses; see pp. 29, 62. Pol, Undetermined

100.00

Comparison Figures for Milling Process .

Sucrose Extraction; see pp. 16, 21, 27. Pol Extraction; see pp. 16, 21, 27. Extraction Ratio (Sucrose); see pp. 16, 21, 27. Extraction Ratio (Pol); see pp. 16, 21, 27. Reduced Extraction (Sucrose); see p. 22. Reduced Extraction (Pol); see p. 22. Milling Loss (Sucrose = Pol); see pp. 16, 21, 27. Absolute Juice in Bagasse, per cent. Fibre; see p. 22. Undiluted Juice in Bagasse, per cent. Fibre; see p. 22.

Comparison Figures for Boil ing House. Boiling House Recovery (Sucrose); see p. 32. Boiling House Recovery (Pol); see p. 32. Boiling House Recovery, E.S.G.; see p. 34.

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Reduced Boiling House Recovery, E.S.G.; see p. 35. Molasses Factor; see p. 39. Boiling House Performance (Optional); see p. 34.

Overall Comparison Figures.

Overall Recovery (Sucrose); see Sucrose Balance, also p. 36. Overall Recovery (Pol); see Pol Balance, also p. 36. Reduced Overall Recovery, E.S.G.; see p. 36. Yield of E.S.G., see p. 36. Reduced Yield of E.S.G.; see p. 37.

REFERENCES. 1. Arch Suikerind, 35, II, 811 (1927). 2. Arch Suikerind, 36, II, 691 (1928). 3. For a discussion of the various criteria see also

Sijlmans, Proc. I.S.S.C.T. 1929, 533, Deerr, ibid., 552, Proc. I.S.S.C.T. 1932, Bull. No. 1.

4. Deerr, I.S.J. 35, 214 (1933). 5. "Methods of Chemical Control", H.S.P.A. (1931). 6. Arch. Suikerind, 38, I, 261 (1930). 7. Arch. Suikerind, 39, I, 58 (1931). 8. Kerr and Cassidy, I.S.J. 40, 180 (1938). 9. I.S.J. 37, 75 (1935).

10. Bur. Sug. Expt. Stns. Qld. Tech. Comm. 1937, No. 6. 11. I.S.J. 38, 276 (1936). 12. I.S.J. 40, 137 (1938). 13. J.I.E.C. 2, 341 (1910). 14. ibid., 15, 737 (1923). 15. T.S.J. 35, 476 (1933). 16. Facts About Sugar, 25, 568 (1930). 17. Arch. Suikerind, 37, I 557, II, 1081 (1929). 18. Bur. Standards Tech. Paper No. 38 (1927). 19. "Methoden van Onderzoek" 6th Ed. (1931). 20. S.A. Sug. Tech. Assn. Proc. 8th Congress. 21. Arch. Suikerind, 35, III, 107 (1927). 22. I.S.J., 17, 213 (1915). 23. Jnl. A.O.A.C., 8, 384 (1925); 9, 166 (1926); 10, 183 (1927); 11, 167

(1928); 12, 158 (1929); 13, 188 (1930); 14, 172 (1931).' 24. I.S.J., 25, 143 (1923). 25. I.S.J., 34, 353 (1932). 26. Proc. Q.S.S.C.T. 1936, 101; 1938, 29; 1939, 43. 27. Proc. Q.S.S.C.T. 1950, 217. 28. I.S.J. 34, 213 and 460 (1932). 29. Z. Ver deut Zuckerind 71, 123 (1921). 30. I.S.J. 39, 300 (1937). 31. Arch. Suikerind, 37, III, 781 (1929). 32. Facts About Sugar, 17, 552 (1923). 33. Z. Ver deut Zuckerind, 75, 763 (1925). 34. Proc. S.A. Sugar Tech. Assn., 1931, 23. 35. I.S.J., 29, 372 (1927). 36. Full details are given in Lab. Manual for Qld. Sugar Mills 3rd Ed., 1954. 37. Schmidt, Wiggins and Yearwood.

Proc. B.W.I. Sug. Tech., 1951, 171.

82

APPENDIX I. Introduction.

The accepted standard system of metrology for international purposes is the metric or c.g.s. system. Its use is obligatory in many countries and optional or partially compulsory in most others. Of the alternative systems the American and the British, which in most respects are identical, have the greatest significance for the sugar industry. Numerous other systems of weights and measures are in use throughout the world but they operate mainly for local usage and are restricted to fundamental units or simple derivatives thereof. Perhaps the most commonly encountered in the parlance of the sugar industry are the units of Spanish origin.

It is fortunate that the sugar technologist, in converting units from one system to another, is rarely interested in preserving the highest degree of accuracy. If this is attempted it is necessary to recognise that there are slight differences of opinion as to some of the fundamental figures, and many of the relationships normally regarded as constant actually vary slightly over different ranges of temperature or other influential factors.

In the Tables and notes which follow, the significant figures rarely exceed four, which is more than sufficient to accord with the general standard of technical calculations in the sugar industry. It behoves any person seeking a high degree of accuracy to resort to more specialised publications where the conditions applying to some of the relationships are precisely stated.

The Tables have been restricted to American, British and Metric units. Conversion figures have been applied for some other units known to be in regular use. In regard to the latter it should be noted that a unit may differ in magnitude from country to country though the name remain unchanged.

Linear Measure Equivalents.

1 Cuban vara = 0.848 metres = 33.385 inches 1 Spanish vara = 0.836 me. = 32.91 inches 1 Spanish pulgada = 2.322 cm. = 0.9141 inches

Surface and Area Equivalents.

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The are is an area of 100 sq. m. The multiple, Hectare = 100 ares is in more common use. Some other measures of area are—

The arroba is frequently quoted as a measure of weight, though the actual weight of the arroba varies from country to country. The Cuban arroba has been standardised accurately and may be taken as equal to 25.353 lb. avoir. = 11.5 kg. Except in Brazil and Colombia these quoted weights may be accepted for the arroba with only slight error. The arrobas of Colombia and Brazil are heavier, weighing 27-5 lb. (12.5 kg.) and 32.4 lb. (14.7 kg.) respectively. A quintal is a weight of 100 pounds (local system) or 4 arrobas. The term quintal may also be applied to 100 lb. avoir. and no great error will be incurred by rating the quintal generally at 100 lb. avoir, or one-twentieth of a short ton. A weight of 100 lb. may also be termed a "short hundredweight". The normal hundredweight is of 112 lb. avoir. The metric quintal is of 100 kg. (220.5 lb. avoir.).

Whereas the long ton is generally used, as the " ton" in British countries. American usage of the term " ton" generally signifies the short ton. The metric ton lies intermediate between the two but may be considered equal to the long ton for approximate calculations. The short Spanish tonelada is of 2000 Spanish pounds = 2028 lb. avoir. The long Spanish tonelada = 2240 lb. Spanish = 2272 lb. avoir.

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Mass Equivalents.

Some other weight units are—

One must be constantly on guard against confusion between the two "gallon" units of the English-speaking peoples. Fortunately the ratio relat­ing the two is simple—10 : 12 so that they are readily interconvertible. The problem is solved when volumes are specified in cubic ft. In the metric system, for larger volumes, the Hectolitre = 100 litres is commonly used.

Density Equivalents.

85

Pressure Equivalents.

Volume and Capacity Equivalents.

* 1 cal. per sq. cm, = 10 Cal. per sq. m.

Conversions of Some Common Unit English—Metric Systems

Length— Factors

Inch x 2.54 0.3937 x cm.* foot x 0.3048 3.281 x m. vard X 0.9144 1.0936 x m. mile x 1.6093 0.6214 x km.

* To convert a dimension in inches to centimetres multiply by 2.54. To convert a dimension in centimetres to inches multiply by 0.3937.

Approximate Equivalents for Mill Sizes

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Heat Flow Equivalents.

Heat, Energy and Work Equivalents.

Volume— cu. in. x 16.39 0.061 x cc. cu. ft. x 28.32 0.0353 X litre. Imp. gal. x 4.546 0.22 x litre. U.S. gal. x 3.785 0.264 x litre. .10 cu. ft. per short ton = approx. 3.1 HI. per metric ton. 1 Imp. gal. per sq. ft. = 49 lit. per sq. m. 1 U.S. gal. per sq. ft. = 41 lit. per sq. m.

Weight- -oz. (avoir.) x 28.35 0.0353 x g. lb. (avoir.) x 0.4536 2.205 x kg. short ton x 0.9072 1.102 x metric ton. long ton x 1.016 0.9842 x metric ton.

Pressure— lb. per sq. in. (p.s.i.) X 0.0703 14.22 x kg. per sq. cm. 1 kg. per sq. cm. = approx. 1 atmosphere. 1000 p.s.i. = approx. 70 kg. per sq. cm. = 68 atmosphere. 10 short tons per ft. = approx. 3 metric tons per dm.

Heat — Btu. x 0.252 3.97 x Cal. Btu./sq. ft. x 2.71 0.369 X Cal./sq. m. Btu./sq. ft./°F. x 4.88 0.205 x Cal./sq. m./°C. Btu./lb. x 0.555 1.8 x Cal./kg.

Power— 1 H.P. (abs.) = 550 ft. lb./sec. = approx. 746 watts. 1 C.V. = 75 kg. m./sec. = 735.5 watts. H.P. x 1-014 0.896 x C.V.

Condensed Temperature Conversion Table Equivalents

°C. °F. °C. °F. 0 32 110 230

10 50 120 248 20 68 130 266 30 86 140 284 40 104 150 302 50 122 200 392 60 140 250 482 70 158 300 572 80 176 350 662 90 194 400 752

100 212 Interpolations

87

APPENDIX II. Standard Tables.

Although there are minor differences to be observed between correspond-ing Tables published in various works, for the most part these differences arise from either slight variations in the basic data used in the compilation of the Tables or genuine differences of opinion as to the facts. In the former class one may mention as basic data such items as the density of air, the density of weights and the coefficient of expansion of glass. None of these is a fundamental constant and one man's choice, whilst differing from that of another, may have equal claim for adoption. In the latter class may be mentioned such data as those pertaining to the densities of sugar solutions of various strengths at various temperatures. In this field there are significant differences of opinion and he is either very confident or very foolish who will say that these figures on the one hand are correct and those on the other hand are wrong.

Viewing the whole matter one is led to conclude that , where differences exist below the level of practical significance, what matter; where the differ-ences are significant there is strong presumptive evidence of a lack of funda-mental knowledge—then let the user beware. One excepts from consideration the thought that any country will use Tables without being satisfied as to their basis on accepted facts or reliable determinations.

These arguments are considered to render it not only unnecessary but also unwise to publish a set of standard Tables in this book for use by the sugar manufacturers of the world. At the same time no harm, can be done by drawing attention to some sources and some features of the basic Tables in general use.

Densities of Sugar Solutions. The standard Table usually adopted is that published in Circular 44

(1918) of the U.S. Bureau of Standards and the International Critical Tables Vol. II , p. 343. In using these Tables it is necessary to recognise that the densities and specific gravities quoted are in vacuo. The corresponding figures for conditions "in air with brass weights" can be worked out by any competent physicist. Practical Tables of a lower degree of accuracy, based on weights in air are available from Circular C440 (1942) of the U.S. Bureau of Standards.

Temperature Corrections for Brix Hydrometers . Probably the most generally adopted Table of temperature corrections

for Brix hydrometers is tha t printed in Circular 19 (1914) of the U.S. Bureau of Standards. This Table is based on the original data of Plato, Z. Ver deut. Zucker Ind. 50 II (1900) and is qualified by the statement that it applies to spindles made of Jena 16111 glass. One wonders how many spindles in the world to-day are made of such glass ! The Table is also accompanied by a warning that the figures are approximate for temperatures differing appreciably from the standard.

Comprehensive investigations into the density characteristics of sugar solutions were undertaken at the Java Proefstation in 1930 (Mededeelingen van net Proefstation 1930 No. 18) and these led to the compilation of a Table of temperature corrections for Brix hydrometers standardised at 27£° C. This Table is puzzling at first sight as the temperature correction departs from zero at 27£° C. at Brix levels above zero. At 70 Brix the temperature of zero correction is over 28° C, and this appears incompatible with the concept of a spindle being standardised, and therefore reading correctly, at 27£° C. The explanation, to the best of the writer's knowledge, is that the correction Table applies to spindles previously calibrated to read concentra-tions expressed relative to weights in air. The Table thus combines two

88

corrections, one for temperature and the other to reduce the Brix values to the proper relationship with concentrations based on weights in vacuo. The actual data relative to the thermal coefficients of expansion of sugar solutions used in this work were primarily those of Plato.

For any selected Brix the difference between the readings of a 20° C. spindle and a 27½ ° C. spindle should be independent of temperature. These differences appear to be established with good agreement. Some typical figures are:— Brix 0 10 20 30 40 50 60 Difference in readings . . 0.43 0.46 0.50 0.54 0.57 0.59 0.60

The use of these differences facilitates the conversion of a 20° C. Table to a 27½° C. Table or vice versa. When five Tables, originating in Hawaii, India, Java, U.S.A., and Queensland were brought to a common basis of temperature and checked it was found tha t in the overwhelming majority of cases the readings did not differ by more than 0-01. The exceptions were some divergencies in the Indian Table at 35° C. and in the Hawaiian Table above 60° C. This review indicates that there is satisfactory agreement as to the values applying under normal conditions of operation. Under extreme conditions all available figures must be regarded as approximate.

Refractometer Brix:. Standard Tables of both Brix-Refractive Index relationships and

Temperature Corrections were adopted by the I.C.U.M.S.A. in 1936. No further comment is necessary.

Schmitz's Table. The derivation of Schmitz's Table is based on the formula

Normal Weight x Polariscope Reading Weight of 100 ml. solution in air

For the purpose of computing a Table based on Brixes observed with a spindle standardised at temperature t the denominator of the expression above may be equated to—weight in air of 100 ml. water at temp, t x S.G.t

/t corresponding to any selected Brix.

Some of the Schmitz's Tables in use appear to be survivors of earlier days, when the proper method of derivation was not clearly defined. There is no excuse now for significantly different versions except in relation to the two differing standard temperatures for Brix spindles. So far as is known, polariscopes are all standardised at 20° C.

Solubility of Sucrose. Though figures pertaining to the solubility of sucrose in water do not

enter into the factory control system, they are involved in several recognized determinations. Hence a Table of solubilities of sucrose in water at various temperatures finds a place in every sugar handbook. The most commonly encountered figures are those of Herzfeld (Z. Ver. deut. Zuckerind, 42, 181, 1892), but an alternative Table after Grut (T.S.J. 1940, 1941) is sometimes adopted.

W. S. Wise of the Imperial College of Tropical Agriculture has stated (I.S.J. 56, 69, 1954)—"The available data on the solubility of sucrose . . . . reveal the surprising fact that the solubility of sucrose is not very accurately known; above 50° C. especially the results of other investigators diverge markedly from those of Herzfeld which are widely accepted".

Criticism of Herzfeld's figures was voiced earlier by Millicent Taylor (I.S.J. 50, 292, 1948) who investigated solubilities mainly in the region from 64 to 82° C. She found solubilities slightly lower than those reported by

89

QUT Library

' "Herzfeld at temperatures below 62° C, and appreciably higher at tempera-tures round 80° C. Above 62° C. the values determined by Miss Taylor lay between those of Herzfeld and Grut. Wise, in 1954, did not refer to the work of Miss Taylor, but examined the data of Herzfeld and Grut in relation to velocity of crystallization. He concluded that , above about 50° C, the values nominated by Grut appeared to be more nearly correct than those of Herzfeld. Wise's work involved a linear extrapolation the validity of which is not beyond dispute.

The differences between the several Tables are significant at the higher temperatures. At about 80° C. the difference between the saturation tempera-tures according to Herzfeld and to Grut is about 3.5° C, which is somewhat in excess of the error of determination in practice.

The available evidence leads to the suspicion tha t the solubilities accord-ing to Herzfeld are too low at temperatures above about 60° C, whilst those of Grut are slightly high. The intermediate values proposed by Miss Taylor appear to be the best available at present. According to Miss Taylor the solubility curve is represented by the formula,

C = 63.608 + 0-1322t + 0 .000722t2

where C is the concentration in g. sucrose per 100 g. solution and t is the temperature °C.

90