THE NITROGEN OF PROCESSED FERTILIZERS. 7 
the phosphotungstatcs were almost redissolvcd, when it was set aside 
for 48 hours in order to allow them to recrystalUze 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 soUd 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 18 per cent of the nitrogen of cystine is spUt off as ammonia. 
Total nitrogen in tJie 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 Slj^ke apparatus.^ 
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 IST- 1.125 arginine N; 
(2) Lysine N = total N — (arginine N -f 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. fiask 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 foimd 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). 
