THE NITROGEN OF PROCESSED FERTILIZERS. V 



the phosphotungstates were almost redissolved, when it was set aside 

 for 48 hours in order to allow them to recrystallize and fully pre- 

 cipitate. The precipitate was then filtered, washed, and dissolved 

 in 45 per cent sodium hydroxide as described by Van Slyke. The 

 phosphotungstic acid was precipitated with barium chloride and 

 filtered off. The filtrate and washings from this precipitate were 

 concentrated in vacuo and made up to a volume of 200 c. c. 



Arginine nitrogen. — Arginine nitrogen was determined in 100 c. c. 

 of this solution by boiling with 12.5 grams of solid potassium hydroxide 

 for six hours and collecting the ammonia formed in 0.1 N sulphuric 

 acid. Under these conditions one-half of the nitrogen in the arginine 

 and 1 8 per cent of the nitrogen of cystine is split off as ammonia. 

 * Total nitrogen in the diamino acid solution. — Total nitrogen in the 

 diamino acid solution was found by subjecting the solution remaining 

 after the arginine determination to Kjeldahl analysis and adding to 

 the ammonia so obtained the amount obtained from the arginine nitro- 

 gen determination. 



Amino nitrogen. — Amino nitrogen was determined by means of the 

 Van Slyke apparatus. 1 



From these three figures the nitrogen was calculated as arginine N, 

 histidine N", and lysine N according to the two formulas: 



(1) Histidine N= 1.667 non-amino N— 1.125 arginine N; 



(2) Lysine N = total N— (arginine N+ histidine N). 



The results obtained were as follows: For the water extract argi- 

 nine 0.111 per cent, histidine nitrogen 0.117 per cent, and lysine nitro- 

 gen 0.081 per cent; for the hydrochloric-acid extract they were 

 0.104, 0.070, and 0.117 per cent, respectively. 



Total nitrogen of the monoamino acids. — To the combined filtrate 

 and washings from the phosphotungstic acid precipitate 45 per cent 

 caustic soda was added until the solution became turbid by the pre- 

 cipitation of lime; acetic acid was then added until the solution 

 cleared. This solution was placed in a 500 c. c. flask and made up to 

 the mark. Total nitrogen was estimated in 100 c. c. portions, using 

 the Kjeldahl method. 



Amino nitrogen. — Amino nitrogen in the form of monoamino acids 

 was determined by use of the Van Slyke apparatus. 



From the two figures obtained the amount of nitrogen present as 

 non-amino nitrogen in monoamino acids was found by difference. 

 The amino nitrogen in the form of monoamino acids in the water 

 extract was 0.543 per cent and in the hydrochloric acid extract 0.546 

 per cent. The non-amino nitrogen in the monoamino acid fraction of 

 the water extract was 0.114 per cent and in the hydrochloric acid 

 extract it was 0.133 per cent. 



1 For the description of this apparatus and the details of the procedure employed, see: Van Slyke, Jour. 

 Biol. Chem., 12, 275 (1912). 



