D.P .H .

The Analysis of Water,

Fre» and Saline Ammonia, (P .A ,)

This determination la one of the most important but it hsib% be considered, when it comes to interpretation of the figures, in eW r junction with the other figures of the analysis , In particular the free ammonia figure must be compared with those of albuminoid ammonia, nitrate nitrogen and nitrite as the preportion in which tho*o forms of nitrogen are present may give valuable information about the degree and nature of organic pollution. These different forms of nitrogen in combination happen to be analysable by simple methods and it is for this reason that nitrogen is chosen as a convenient index of the degree and state of pollution.

Organic matter, whether animal or vegetable, consists of a mixture of complex substanoes wh?se accurate analysis is impossible but the vicissitudes of the nitrogen contained in them can be followed with comparative ease. In water the organic matter is both vegetable and animal - some of it has already been simplified in chemical structure by enzvmatic-.d1gestlon and microbiological action and this simplification in structure continues in nature, i ,e , in soil and water with the formation of free and saline anraonla. As time elapses and if the microbiological conditions are suitable, this ammonia is oxidised in the first instance to nitrite and then to nitrate. Further oxidation can not take place and nitrate is only prevented from accumulating by the fact that vegetable life is capable • f synthesizing nitrate back again into vegetable pretein.

Free and saline ammonia then is usually derived fr*m organic matter and is an index of recent pollution whereas nitrate, aSfa.ugh indicating pollution, is evidence that the p*llutltn from which it was derived was more remote because time is required f*r the exida- tion of the nitrogen of ammonia to the nitrate form.

Albuminoid ammonia is the ammonia which can be split ®ff from the organic matter in water by means of special chemical oxidising methods and therefore represents organic matter which is still in a complex form not yet broken down by natural agencies to the farm of free ammonia.

Estimation of Free Ammonia of Water - Wanklyn Process,

The apparatus required is (1) a flask of about 1500 c .c . capacity,(2) a condenser, (3) a set of Nessler glasses graduated at 50 c,o , in a stand, '

The chemicals required are (1 ) sodium carbonate, (2) Nessler’s solution which gives a yellow colour with the ammonium ion, (3) a standard solution of ammonium chloride of such strength that 1 c .c , = 0,01 mgm. of NH3 , (4) ammonia free distilled water. The chemical change may be represented

2KI,HgIg NH3 NHg«I

--------- 7(Nessler reagent) (yellow)

After setting up the apparatus it must first be made anuaonift. as glass and rubber absorb ammonia from the air of the laboratory. Into the flask are placed about 200 c .c. of ammonia f»ee distilled water together with a pinch t if sodium oarbenate to set free the ammonia from any ammonium salts which may be present. Distil ever 50 c.c. into a Nessler glass, add to the distillate 2 c .c , of Nessler’ s solution and examine the mixture in a good light locking

down through the depth of the liquid, A clean white tile should bo

\

placed under the glass and the bottom of the glass should be dried.If any colour is present, showing the presence of ammonia, the distillation must be continued till the distillate gives no colour on Nesslerization. When the apparatus is free of ammonia,. 500 c.c. of the water sample carefully measured in a measuring flask, are poured into the distilling flask, care being taken to see that enough sodium carbonate is present to ensure alkalinity (ammonia will not distil over from an acid liquid). Boil steadily and collect the distillate in Nessler glasses until three l®ts of 50 c.c. have been collected* In most instances the third glass will be found to be ammonia free, The amount of ammonia in the first two glasses has now to be estimated by comparing the colour on Nessleri* zing with the colour produced by a known amount of ammonia. Int» a series of Nessler tubes place say 2 c .c ., 2 .5 c .c ., 3 c .c ., 3.5 c.c.4 .0 c .c . of the standard solution of ammonia and make up te 50 c .c . with ammonia free distilled water (a different range may be required according to the amount of ammonia which the water sample contains). To each of the distillate glasses and to these standards, 2 c . c . « f Nessler*s solution are added, followed by careful mixing, and standing for 2 minutes. In a good light and in the same manner as before the glasses are inspected and matched.

Supposing the colour of the first 50 c .c. of distillate matched 4 .0 c .c . of standard solution, and the second glass matched2 . 0 c .c . of solution, then the calculation is:-

500 c .c . of the water yielded 50 c .c. matched by 4 .0 c .c . of S.S.

50 c .c . " " 2 .0 c .c . 11 a s .

a total of 6 . 0 c 0c. S .S , ammonium chloride.

But 1 c .c . S .S , = 0,01 mgm, NH3

. . 500 c.c. of the water = 6 .0 x 0 .01 mgm. NH3

. . 100 c .c . of the water = 0.06 = 0.012 mgm. NH3

5

i .e . Free Ammonia = 0,012 parts per 100,000,

If the colour match of the sample comes between two of the standards, e.g, between 2 ,0 c ,c , and the 2.5 c .c . standards, then further quan­tities of the S .S . ammonium chloride can be run into the 2 .0 c .c . standard from -a- microburette until an cxact match, e .g . 2 .3 c .c ., is obtained.

If the matching is not perfect another method of obtaining a more accurate result is to pour the darker of the two liquids into a measuring cylinder and then pouring it back slowly Into the Nessler glass until the tints exactly match and finally measuring the volume remaining in the cylinder. Supposing It was found that the first distillate of 50 c .c. was slightly darker than the4 . 0 c .c . standard, and that 46 c .c . exactly matched. Allowing for the added 2 c .c . of Nessler, the original volume was 52 c .c , and therefore

~ x 4 x 0.01 mgm. NH3

is the amount present in the first 50 c.c. of distillate.

Another method used if the amount of ammonia is considerable is to pool the distillates and match an aliquot part of It.

Direct Nesslerization does not give such accurate results as Nesslerization after distillation.

A preliminary Nesslerization is useful as a guide to the amount ©f water to be used for distillation. If there is a definite ammonia colour then only 250 c.c. or less of the water sample would bo used; if there ia an actual precipitate, as with many sewages, then 20 c .c. would probably be ample but it would have to be diluted with a sufficient volume of ammonia free water before distillation.

Albuminoid Ammonia. (A .A .).

The apparatus used is the samo as for the F.A. and the only additional solution needed is a solution of potassium permanganate made strongly alkaline with caustic soda. About 50 c .c . of this solution are taken, mixed with 50 c .c . of distilled water and boiled in an open beaker until the volume is reduced by about one half.This ensures that all ammonia is removed from the reagent.

Test.

'This is performed on the residual liquid left in the flask after the distillation of the P.A. This residuum contains no F.A. but contains the organic matter from 500 c .c . of the water sample. The flask is allowed to cool somewhat, some pumice is added to prevent bumping and finally the alkaline permanganate is introduced. Distillation Is started and maintained at a slow rate until three or four lots of 50 c .c . have passed over. Nesslerizlng and matching are performed as for the F.A.

It will be found that the alkaline permanganate has decomposed some of the organic matter and set ammonia free.

The second half of the process (A .A .) is not quantitative only about half the possible figure is obtained, but this is a useful index.

With the F .A . it is also sometimes found that ammonia comes over almost indefinitely. This is more particularly the case if too much NagCOg has been added, for this decomposes such nitro­genous rubstances as urea.

As illustrations of the F .A . and A.A. found In various waters we may take the following:

River Riverf i l ­tered

Sea Sewage Effluent Peat Foul ,Green-sand

CountryRain

Town ij Rain |

F.A. 0.006 0 .0 0 0 2 0 .0 0 1 6.5 1.5 0 ,0 0 1 0 .0 2 0,03 0.05 0.14 |

A.A.

J.........

0 .0 1 0.0043 0.004 1.4 0.15 0 .0 1 0 .0 1 0 .0 0 1 0.005 0.015 j

General Interpretation.

If A.A. = 0.005 and F .A . ^ 0.005 and also Cl and nitrate figures are high, there is animal pollution.

If F .A . is low, 0.002, then A.A. may go up to 0,01 If nitrate and Cl are low - it Is due to vegetable matter.

If A. A. is much below 0,005 then a high P.A, is probably due to1

a reduction of nitrates by stratum, E.G. green-sand.

safe.Under certain circumstances P .A , is high but the water is •

(1) Reduction of nitrate by green-sand(2) Reduction of nitrate by cement and iron pipes or storage in

galvanized iron tank(3) Ammonia stratum(4) Rain water - through ammonia in the air.

Never judge a water from an examination of the N. figures alene.

Nitrites

The presence of these is usually estimated only qualitatively but the following tests can be used for quantitative determination by comparison with standard nitrite solutions.

Test

$t)+luHrW ^ To 50 c *c* of the water in a Nessler glass, add 1 c .c . of •f/./^fe^A^Pkurio acid(l:4) followed by 1 c .c . of the solution of meta-

r phenylenediamine. Mix and allow to stand, A brown colour indi- cates nitrite. The maximum colour is not attained until 20 minutes

$tt»f̂ Cr6rha.ve elapsed. [This reaction depends on the formation of Bismark or tri-amino-azo-benzine, ]

^ To 5 0 c#c* of thQ water *n a Nessler glass add 1 c .c . of j l u i sulphanilic acid solution followed by 1 c .c . of the solution of alpha-

naphthylamine. Mix and allow to stand for 10 minutes. A red colour is produoed in the presence of a nitrite. *—

Nitrates

Test

{ 1) The qualitative test is to mix about 5 c .c . of the water with 3 c .c . of a saturated solution of brucine. Then perform a ring to3* by pouring nitrate-free sulphuric acid slowly into the tube

\ held ssLant. At the junction of the liquids when the tube is slight- il //* ^ agitated a pJjjk: colour will form in the presence of nitrates.

This colour rapidly changes to yellow if much hitrate is present.

b ^ - VlA'$ 2 ) Nitrates may be estimated quantitatively in the two following ways.

Phenol-Sulphonic Process

Place two shallow porcelain dishes on the water bath, pipette //)•<• H /) in t0 one ^ accurate 10 c .c . of the sample and into the other 10 c.c« ^ ■ T of a standard solution of potassium nitrate of strength 1 c .c . = 0 .0 1 WprW* mgm. of nitrogen as nitrate. Evaporate to dryness and then add to

each 3 e .c . of phenol-suphoni^acid and allow to remain for a few 31 ̂| W ^ minutes on the boiling water bath. Take two Nessler glasses and -f a ama11 amount of distilled water in each. Then pour theWvfl&U. contents of the dishes into their corresponding Nessler glass. Add f-4/ u strong (25%) ammonia or strong K0H to each dish carefully and slowly

to avoid spurting, and pour iAto the Nessler glass. Repeat thisalkaline washing two or three fP c»p» ^ 0 presence of rligquid has been fully allialinfr -

times, and then make up the volume to itrate and provided that the

''f _ •>- /;? , ^

Jir I C f ^ _ , - ^ r; ~~ o o / PK i-t&t ^ @ f ̂Am , ' *." e b t u + t j % - ^X ji ' / Q..̂ ~~c.,

I» (

~ O V .<D /

^ Jk'r '

« ’ > ^ 2 < ^ . '

f ? v >o t y /try- V <\

b ‘ O i y

5 ^ .. n| 8 .1

- « % ' '

' M . V "

• . ^\ y / & V /

a yellow colour is produced. This colour is proportional to the amount of nitrate present and the subsequent procedure is to match the colours of sample and standard. With most waters the standard will he of deeper colour than the sample. Taking the usual pre­cautions in matching colours, i .e . to look through the depth of the liquids in a good light, some of the liquid frem the standard is poured off into a 50 c .c . graduated cylinder, and the colours are again compared. If the standard is still too dark more of the liquid is poured off into the cylinder or if it is now too light in colour some of the liquid is returned from the graduated cylinder to the Nessler glass. When an accurate match has been obtained the volume of liquid in the graduated cylinder is noted. Supposing that 33 c .c . of liquid have had to be removed from the standard glass before a match is obtained:

It is clear then that the colour produced by tho nitrate in 10 c .c . of the sample is equal to the colour produced by 50-33 c.c. of the diluted standard solution of nitrate of which 10 c .c . was evaporated at the beginning of the test.

Therefore

10 c.c. of the sample = 50-33 c.c. of diluted standard

c ,c * ^ e

17of 10 c .c . x 0 .0 1 mgms. of

0 nitrate N

= 0.034 mgms.

Therefore 100 c.c. of sample contain 0.34 mgms. of nitrate N

or the amount of nitrate nitrogen present in the sample = 0.34 partsper 1 0 0 , 0 0 0 .

Zinc-Copper Couple Process.

This method is very often employed in preference to the phenol- sulphonic process. The principle of the process is that nitrates (and also nitrites) are reduced to ammonia when in contact with a zinc-copper couple in acid medium. The ammonia Is then determined.

The couple is prepared by placing some granulated zinc in a flask, washing with 25 per cent, sulphuric and then distilled water, then adding a solution of copper sulphate which must remain for about 15 minutes. The zinc becomes covered with a black deposit of copper. After careful washing a measured amount of the water sample is added - the amount of the water added depending on the amount of nitrate which preliminary experiment has shown to be present. A few drops of dilute HC1 are added and the flask is incubated at 37°C. for at 3e ast an hour or for a longer period if no incubator is at hand.

The liquid contents of the flask are now carefully washed out into a distilling flask which contains about 200 c.c. of distilled water and has been rendered ammonia free in the usual .way. Distillation and Nesslerizing of the distillate is carried out exactly as in the determination of saline ammonia. From the ammonia thus found the equivalent of the nitrate nitrogen present is calculated.

Special care crust bo taken to see that the contents of the distilling flask are made alkaline. An alternative method is to Nesslerize direct without distillation: to the liquid after treat­ment with the zinc-copper couple dilute oaustio soda is added care­fully until all the zinc In solution has been precipitated as hydro­xide. The hydroxide is filtered off and an aliquot part of the clear liquid is now Nesslerized direct and the c*lour compared with a suitable strength of the standard ammonia solution.

It is to be noted that the zi no-copper couple method will give a figure which includes not only the nitrate nitrogen but also the nitrite nitrogen and the free ammonia* If tflie laat two are con* siderable In amount their values as separately determined will have to be subtracted from the total in order to obtain an accurate result.

I

Collection Number: AD843

XUMA, A.B., Papers

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