T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
998
Vol. j , No.
ON THE PREPARATION OF NEUTRAL AMMONIUM CITRATE SOLUTION'
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and 4 4 . j 4 grams of ammonia per liter. The gravity of this solution was 1 . 0 9 . This solution was assumed B y P A U L RUDNICK AND w. L . L A T 5 H A W to be practically neutral and of the proper strength, It has been t h e custom in this laboratory for several although when tested by t h e indicator method of Hand years past t o determine t h e strength of neutral am- it seemed t o be very slightly acid. This was in acmonium citrate solution b y t h e analytical method cordance with the ratio of ammonia t o citric acid, recommended b y t h e Committee on Ammonium Citrate namely I : 3.786 instead of I : 3.765. Solution of this Division in 1 9 0 9 , ~except t h a t no Solution I1 was made up of a higher concentration a t t e m p t was made t o determine t h e citric acid content t h a n t h a t required by the official method and was b y titrating back t h e residue after distillation of t h e then brought t o neutrality as follows: ammonia. It was found simpler and easier t o deterInstead of following strictly t h e method of Hand mine t h e strength in this way and t o calculate from this a series of tubes was prepared from Solution I as strength t h e extent of dilution necessary t o bring t h e described by Hand, namely adding j cc. of t h e amsolution t o t h e strength recommended, i. e., 43.7 monium citrate solution t o 4 j cc. of neutral water grams of ammonia per liter, t h a n t o dilute t o the re- containing the prescribed amount of azolitmin indiquired specific gravity b y cut-and-try methods. A cator. One of these tubes was left unchanged and t o determination of t h e specific gravity of t h e solution the remainder were made successive additions, differthus prepared is always made as a final check and is ing by 0.5 cc. each, of N / I O ammonia and N / I O always found t o be 0.09 * 0 . 0 0 1 , substantially as citric acid, respectively. From these tubes t h e one required by t h e official method.s apparently nearest neutral was chosen and Solution The determination of t h e neutrality proper, how- I1 was then adjusted t o this color b y t h e method of ever, has not been made b y determining the citric Hand. Instead of comparing t h e tubes as described acid as recommended by t h e committee, b u t is made by him, however, we found i t much easier t o compare b y t h e indicator method recommended b y Hand14 them in a Craven-Jennings colorimeter' in the same which has proven fairly satisfactory in our hands so manner as in nesslerization of water. Solution I1 was then analyzed by t h e Patten and far as ease of manipulation and simplicity were conMarti method and was found t o contain 179.2 grams cerned. The electrical conductivity methods proposed b y of citric acid and 47.80 grams of ammonia per liter, Hall and Bell6 and later b y Patten and Robinson6 giving a ratio of I : 3.748 as against I : 3.765, the as well as t h e extraction and temperature methods ratio given by Patten and Marti. Solution I1 was proposed by Bell and Cowell' do not seem applicable then brought to a gravity of 1.09. We now had two solutions, one of which (Solution t o t h e problem as presented in routine fertilizer work for various reasons, chiefly because of t h e difficulties 11) was obviously slightly alkaline, t h e other (Solution of manipulation involved. A most practical method I) slightly acid. Comparative analyses of a sample of attacking t h e problem was advised by P a t t e n of acid phosphate were made with these two solutions, and Martis a n d presented a t t h e last meeting of this giving t h e following results: Division in Milwaukee. T h e great advantage of this PERCENTAGES INSOLUBLE Pa06 B Y method lies both in its simplicity and ease of accurate Solution I Solution I1 1.10 1.11 reproduction, as well as in t h e fact t h a t it is based 1.11 1.10 upon reliable and accurate physico-chemical measureLost 1.12 ments summarized in a definite strength of both amThese results would indicate t h a t the variation of monia a n d citric acid. these solutions from t h e ratio given by Patten and It became a matter of interest t o compare this method Marti was not sufficient t o affect t h e results obtained with t h e method used in this laboratory heretofore on the sample of acid phosphate in question. Further as described above, and t h e following is a n account work on this subject is in progress. of t h e preliminary work undertaken and of t h e results CHEMICAL LABORATORY O F ARMOUR& COMPANY so obtained. UNIONSTOCK Y A R D S , CHICAGO Two solutions of ammonium citrate were prepared as follows: A STUDY OF THE PEMBERTON-KILGORE METHOD FOR Solution I upon analysis by the P a t t e n and Marti DETERMINATION OF PHOSPHORIC ACID B y P. L. HIBBARD method showed a content of I 58.1 grams of citric acid Received Aug. 4, 1913 and 37.23 grams of ammonia per liter. From this After using the Pemberton-Kilgore volumetric the proper correction for both citric acid and ammonia were calculated and a re-analysis of the corrected solu- method for phosphoric acid quite successfully for some tion showed a content of 168.6 grams of citric acid time, sources of error in i t became apparent. Endeavor to avoid these errors led t o t h e making of this study, 1 Paper presented at the 48th meeting of the A. C. S.. Rochester, September 8-12. 1913. which is now published with t h e hope t h a t others * W. D. Richardson, et al., THISJOURNAL, 1, 616 (1909). may be helped in t h e use of this very good method. * Bur. Chcm., Bull. 107, page 1 . I n t h e beginning it is well t o understand t h a t t h e 4 I b i d . 138, page 11. 6 J . A m . Chcm. Soc., 31, 7 1 1 (1911). method is not, nor can i t be made scientifically exact. 6 THISJOURNAL, 4, 443 (1912). Good results obtained in t h e use of it must always be 7 J . Am. Chcm. SOC.,80, 49 (1913).
* THISJOURNAL,
6 , 567 (1913).
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