the concIusion that some error was made in these de- terminations rather than to the assumption tha t the iodine number of an oil may drop and then increase.

Special attention should be focused on the rather moderate changes in constants shown by corn oil, cottonseed oil, lumbang oil, sunflower oil, and hemp- seed oil (Nos. 11, 12, 1 5 , 16 and 17: respectively). These oils were all received in excellent condition and were perfectly clear and apparently free from moisture. These factors may have had much to do with their keeping properties.

TABLE IV RAW LINSEED OIL

Untreated and Sterilized Iodine Sapon.

No. Sp. Gr. No. No. 24 Original Oil

Not Sterilized 0.931 186.0 188.0 Examined 1911 Original Oil Not Sterilized Examined 0.933 185.4 189.6 Nov. 1911 Original Oil Not Sterilized Examined 0.943 182.1 192.3 Feb. 1919 Original Oil Sterilized Nov. 1914' 0.935 181.5 191.8 Examined Feb. 1919

RAW MENHADEN OIL Untreated and Sterilized

25 Original Oil Not Sterilized 0.932 158.0 187.0 Examined 19 1 1 Original Oil Not Sterilized 0.934 156.3 193.7 Examined Nov. 1914 Original Oil Not Sterilized 0.940 156.9 191.5 Examined Feb. 1919 Original Oil Sterilized Nov. 19141 0.938 156.2 190.1 Examined Feb. 1919

1 Heated t o 105' C.

Acid No.

2.0

2 . 8

4 . 8

0.9

3 . 9

16.1

21.3

5 .1

Refrac. Index

,.

1 .4867

1.4831

1.4816

. .

1 ,4850

1.4802

1 .4802

Most interesting results were obtained with Oils 2 0 a n d . 2 1 (American-grown tung oils). These oils have shown but very moderate changes in acid value, although both developed rather high saponifica- tion numbers, and Oil 2 1 showed a substantial de- crease in iodine number. A comparison of the value of glass and tin for storage purposes is shown in the cases of Oils 2 2 and 23. It seems rather curious that the oil stored in tins should have shown more change than tha t stored in glass. This may possibly be due to the action of the fungus growth that was in 1919 observed to be present in the tinned sample. Simi- lar action on the same oil in the glass bottled sample may have been inhibited by the action of light.

TABLB V-MISCELLANEOUS TESTS

No determinations were made a t start of test. Analyses made after allowing oils to remain in glass bottles for nearly

three years. Iodine Sapon. Acid Refrac.

26 Peanut Oil. . . . . . . . . 0.916 87.1 192.4 3.5 1.4696 27 Poppy Seed Oil.. . . . 0.931 133.2 194.3 7.4 1.4767 28 Alfalfa Seed 011 . . . . . 0.926 152.1 186.4 3 .8 1.4791 29 Tung oil^,., . . . . . . . 0.937 153.5 190.1 0 . 8 1.4995

NO. Sp. Gr. No. No. No. Index

1 Source unknown. Very heavy, granular deposit settled out, streaked with fungus growth.

In Table I V some data is given on the effect of sterilization of linseed and menhaden oils by heat treatment. The rapid rise in acid value shown by the unsterilized sample of menhaden oil, and the very moderate rise in acid value shown by the sterilized oil would indicate tha t properly treated oils may be made more or less immune from changes of an undesirable nature. In the writer's opinion the changes that take

A N D E N G I N E E R I N G C H E M I S T R Y 7 61

place in oil upon standing are due very largely to auto- hydrolysis caused by the presence of either moisture or, in some instances, f at-splitting enzymes. When- ever oil is heated to a temperature of 105' C. for a sufficient period of time to remove the moisture, and then filtered, a moisture-free, clear and sterile oil will result. Such oil will apparently keep for a long period of time without showing any marked changes.

TABLE VI-APPEaRANCE O F OILS I N CONTAINBRS I N MARCH 1919,

0% No.

1 '/4 full 2 3/4 full 3 3/4 full

4 =/3 full

5 1/3 full 6 '/a full 7 Q/s full 8 3 / 4 full 9 3/4 full

10 ' / 2 full 11 ' / 2 full 12 '/4 full 13 2,'s full 14 2/3 full 15 2/3 full 16 '/3 full 17 I / 3 full 18 '/a full 19 l/sfull 20 3/4 full

21 '/s full 22 3/a full

23 */a full 24 '/a full

26 S/4 full 27 full

25 '/a full

PREVIOUS TO ANALYSIS

Very slight sediment Vwy clear White sediment a t bottom. Globular-like oxidation a t

surface Completely solidified to white mass, crystalline a t

surface Very clear Highly viscous. Clear Clear. Slight film a t surface Highly viscous White sediment a t bottom.

Clear Slight white sediment a t bottom. Heavy white sediment a t bottom. Dark sediment Clear. Film a t surface Very clear Very clear Very clear Dark sediment a t bottom Dark sediment a t bottom Lower third of oil completely solidified to white mass.

Completely solidified t o white mass Clear. In can 9/10 full. Clear, but sllght fungus

streaks Completely solidified to milk-white mass Very clear Very clear Clear Lower third of oil black mass with white specks through-

Globular-like oxidation a t surface

Clear Clear

Upper part clear

out and a blanket of milk-white granules a t top The precipitated foots and curious form of oxidation products a t the

surface of the fish oils was of a distinctive nature. The solidification of the tung oils t o a white, granular mass is characteristic of these oils when exposed to light for long periods. This condition makes necessary the determina- tion of refractive index a t 60' C. The matter, settled out from the corn and cottonseed oils, was very flocculent and white.

There was unfortunately no analytical data originally obtained on the samples of oils shown in Table V, but a t the end of nearly three years' storage the constants would indicate that but slight changes have taken place in the oils, with the exception of tung oil. This sample was from an unknown source and may have been adulterated.

THE INSTITUT@ OF INDUSTRIAL RESEARCH WASHINGTON, D. C.

WIRE CLOTH AND ITS ADAPTABILITY TO THE CHEMICAL INDUSTRY By ALVIN ALLEN CAMPBELL

Received June 11, 1919

Under the heading of wire cloth there may be numbered over ten thousand different meshes, sizes, and grades. The term wire cloth even to the mind of large users is hardly appreciated to its full extent.

The wire cloth industry was started in Scotland many years ago, and the first plant in the United States was started a t Belleville, N. J., some IOO years ago,

, 7 6 2 T H E J O U R N A L OF I N D U S T R I A L

by some Scotch immigrants. There is still in opera- tion one of the old original hand looms.

In order to give an idea of the possibility of weav- ing from wire a square mesh, the following compari- sons are given: A mesh of 2’/2 in. X z1/2 in. can be made of as heavy rod as I in. diameter and can be made of as light a wire as 0,177 in. There are listed fourteen different sizes of rod and wire in between these two limits. The mesh then gets finer until it reaches 2 5 0 meshes to the linear inch, fabricated from a wire 0.0015 in. in diameter. The wide range of differences can readily be seen from the above state- ment.

I n many instances perforated metals are used as backings for tank strainers, centrifuges, filters, malt floors, washers, etc. The heavier grades of wire cloth are fast replacing this material for the reason that the air space is greater in comparison to the area of the screen than that of perforated metal. The term “air space” is the technical term in the wire cloth indus- t ry for the opening in the mesh. Wire cloth has the advantage over perforated metals from other view- points. I t is stocked in a greater variety of metals, and can be used for sizing materials, because of the very great range of openings and their uniformity.

Wire cloth has long been used in the paper industry, and the majority of manufacturers in the United States still confine their efforts t o the manufacture of Fourdrinier wires or paper machine cloths. Four- drinier wires range in mesh from 40 t o 90, although some tissue mills use wires as fine as IOO mesh.

The manufacturers of the United States had been rather backward in the fabricating of wire cloths finer than IOO meshes t o the inch until about 1912, when some experimental work was started in weaving a piece of zoo-mesh cloth for the Edison laboratories. After overcoming many difficulties, a piece of zoo-mesh cloth 34 in. X IOO f t . was completed, using Monel metal wire of a diameter of 0 . 0 0 2 1 in. This cloth was later used for filtering wax. From that time on Europe has had American competition.

The United States Bureau of Standards in their investigation of testing screens say that it had been impossible for American manufacturers to successfully manufacture meshes finer than IOO

mesh to the inch, and that meshes of the finer nature had to be imported from Germany, France, England and Scotland. While all American manu- facturers listed the fine cloths in their catalogues, they were not American-made goods, in fact, there are still foreign-made goods sold on the American market. Probably 80 per cent of all the wire cloth. especially the fine wire cloth imported from Europe, came from Germany, while the other three countries furnished the balance. A great number of the German manu- facturers were located in Alsace-Lorraine, which will of course now be rated as French. The finest wire cloth on record is 350 mesh, but early in 1914 a firm in Elberfeld, Germany, started to make 400 mesh. If this was accomplished none of it ever came to this country. The finest square mesh manufactured in

A N D E N G I N E E R I N G C H E M I S T R Y Vol. 11, No. 8

the United States is 2 5 0 mesh. All finer is imported material.

All of these fine cloths are confined to a standard, as to size of wire, size of opening, etc. The standard is fixed by the United States Bureau of Standards. American manufacturers do their utmost t o keep up this standard and are constantly in touch with the Bureau.

If a wire cloth is sold as 2 0 0 mesh, i t should measure, within the allowance specified by the Bureau of Standards, 2 0 0 mesh by 2 0 0 mesh, in other words, 200 each way. There are, however, cloths sold on the market as a given num- ber, for instance, as 2 0 0 mesh, which may measure 2 0 0 one way but the other way may measure 185 to 190 mesh. This to the eye is not noticeable, but in work does not give the desired results. The exporters were very fond of sending fine wire cloth into this country, giving it a number which was mistaken by the American buyer as the mesh. For instance, French and German manufacturers would give the number 2 0 0 to a cloth which, when counted, would total only 190 each way, but was bought as 2 0 0 mesh. It cannot be said that this was a deliberate fraud, but in a great many cases the exporter would “get away with it.”

As an example of the necessity of a cloth being per- fect, the following test may be tried: Solder a piece of square mesh 2 0 0 X 2 0 0 in the bottom of a funnel and pass some hydrocarbon mixed with a little water through it. The result will be that all of the water will stay on top of the mesh and the hydrocarbon will pass through. I€, on the other hand, a piece of mesh 2 0 0 X 180 is used, the water will pass through as readily as the hydrocarbon. The explanation is, that the water has a specific gravity different from that of the hydrocarbon; being heavier and globular in nature, i t is held back by the square opening, while the lighter hydrocarbon readily passes through. In the second test, where the mesh is rectangular, the lighter hydrocarbon passes through as readily, while the heavier water, because of its globular nature, elongates and passes through quite as fast.

The user should remember tha t there is a wire cloth available for each individual use, and that some of the larger manufacturers maintain special testing labora- tories in order to assist the user in finding the best mesh for his use.

As before stated, wire cloth covers many meshes, weights, etc.. and in addition i t can be said tha t no matter what the trade name may be, if i t is a woven wire fabric, i t is wire cloth. A few of the trade names follow: Metallic filter cloth, brass lawn-fly screen metallic bolting cloth, wire gauze, platinum gauze, washer wires, Fourdrinier wires, Dutch cloth, centrif - ugal liners, wire mesh, etc.

It is well t o investigate and know wire cloth t o some extent before ordering. There are two different ways of measuring. If an operation calls for a l/4-in. square opening, i t would not be correct to order 4-mesh wire cloth, as 4 mesh is made of thirteen different diameters of wire, ranging from 0.13 j in. as the heaviest size t o 0 . 0 2 8 in. diameter as the lightest size, The term

A word as to perfect cloth.

AW.9 1919 T H E J O U R N A L O F I N D U S T R I A L A N D ENGTNEERING C H E M I S T R Y ' 7 6 3

"mesh" means the number of meshes or openings per linear inch each way, measuring from center t o center of wire. I n the heaviest 4 X 4 mesh the open- ing would measure 0.115 in., whereas in the lightest the opening would measure 0.222 in. I n order t o get a space of 1/4 in. the size wire must be specified along with the size opening. For example, a wire cloth made of 0.083 in. wire with an opening of 0.250

in. would be a 3 X 3 mesh. I t is well for users to write the manufacturers for their catalogue giving table of sizes, openings, etc. The choice of sizes in- creases in the heavier .meshes and decreases in the lighter and finer sizes. There is very little difference in the size of opening and diameter of wire in the meshes finer than IOO X 100. A difference of 0.0001 in. in the diameter of wire would make a considerable difference in the finished product, both from a manu- facturing and working standpoint.

Under the heading of wire cloth, i t should be noted that filter cloths and centrifugal linings are fast be- coming leaders in the chemical industry. Wire cloth is and may be designed t o meet specific pur- poses. Several patents have been issued on filter cloths, and in each case there have been reasons for their design. The latest patent issued by the United States Patent Office' was on a cloth designed to com- pete with, and overcome the deficiencies found in, other filtering mediums.

The factors influencing efficiency in filtration are rapidity, the life of medium, the cost of filtering the medium, the strength of cloth, the fineness of cloth, and the adaptability of the filter cloth t o any make of filter press. It is not the filter cloth which does the filtering; the filter simply acts as a retainer or backing in order tha t a cake may be formed. This medium must be of a nature to permit the filtrate to pass through rapidly and to retain the precipitate. In pressure filtration the cake really does the work, and the quicker the cake forms the more efficient your filter becomes. However. if the cloth becomes clogged, filtration ends or is much retarded. The cloth described in the above- mentioned patent was designed t o overcome the difficulties met with in cloths which must be rolled to get fineness of opening. I n rolling a piece of woven wire fabric i t is impossible to keep equally sized and uniformly shaped openings, and strength is lost in the rolling of wire cloth. When fine overlapping wires such as occur in wire cloth are rolled, these wires are distorted by crushing between rolls. Strength is then sacrificed in order t o get fineness.

This cloth replaces the old type fabric filter cloths, such as jute, hemp, and cotton, being stronger, more readily cleansed, and when made of Monel metal or pure nickel, alkali proof and impervious t o weak acid solutions. Monel filter cloths have stood the commercial use of solutions containing from 7 t o I O

per cent sulfuric acid. The only case known to the writer where Monel metal did not stand up in com- mercial use was in a press using cast iron plates and Monel metal filter leaves for the precipitation of

1 U. S. Patent 1,288,504, December 24, 1919.

potassium permanganate. In this case the filter leaves rapidly decomposed because of electrolytic action set up.

Microscopic examination of this filtering medium shows an opaque surface, when the cloth is parallel with the table of the microscope. If, however, the cloth be turned a t an angle of 45'. small wedge-shaped openings are seen, the idea being to have the contact surface of the filtering medium a practically tight backing for the quick forming of the cake, the wedge- shaped opening permitting a rapid discharge of the filtrate. As stated before, when an opening or mesh decreases to microscopic size, water, because of its globular nature, must elongate in order to pass through i t ; if, however, the hole be rectangular, it will pass through more readily, and even better if the opening be wedge-shaped. I n this weave it is possible t o get twice the number of wires beaten up side by side that would be theoretically possible; for example, 2 5 0

wires of a diameter of 0.004 in. laid parallel and in contact with each other, would equal one inch of space. Because of the weaving principle employed 500 wires are put in this one inch of space. These wires are spirally overlapped, giving a smooth, opaque, double- surfaced filtering medium, the two sides of which are identical, and the openings in which are wedge-shaped, each one identical as to shape and size. A cloth of this nature is very strong and easily cleaned, with a weight of about g ounces t o the square foot. This type of wire cloth is being used extensively as lining for centrifugals.

Wire cloth has been one of the most important materials in the chemical industry during the war-time emergency. It has been used extensively in ordnance manufacture; explosives mills, cement, paper, glue, and pottery manufacture; dyestuffs production, drug houses, color works; food production; and last, but not least, ammonia oxidation.'

NEWARK WIRE C w ~ n COMPANY NBWARK, N E W JERSEY

DETERMINATION OF ANILINE IN DILUTE AQUEOUS SOLUTION

Received March 14, 1919

By WALTER G. 0. CHRISTIANSEN

In plants where aniline is produced the chemist in the works laboratory has t o determine the aniline content of the water from which the aniline has been separated in the rectifying house in order t o ascer- tain how much aniline is being lost in the water. Some days a dozen samples may be brought in, and if each is to be analyzed by extracting a known weight of the sample with ether, drying the extract, evaporating off the ether in a weighed dish, and weighing the residue, considerable time is lost. It is somewhat shorter and more accurate to add two drops of concentrated hydro- chloric acid to the undried ether extract in a weighed dish, evaporate the ether on a steam bath, and dry the residue of aniline hydrochloride in an oven at about 50' C. The residue must not be heated to a high tem- perature, as it decomposes readily. However, either of these methods takes between 3 and 4 hrs.

THIS JOURNAL, 11 (1919), 468, 541.