16 BULLETIN 158, U. S. DEPARTMENT OF AGEICULTUEE. 
There is an increase of 0.47 per cent amide N in the hydrochloric 
acid extract over that in the water extract. This is due to the 
sphtting off of ammonia from some nitrogenous compounds by -the 
hydrochloric acid and suggests the presence of some product of par- 
tial protein hydrolysis in the fertilizer which contains an acid amide 
linkage. 
The statement has already been made that nitrogenous compounds 
other than arginine, liistidine, and lysine are included under the fig- 
ures given for these compounds in the table. This is due to the fact 
that the phosphotungstic acid which is used as a precipitant of the 
diamino acids also precipitates peptones, proteoses, etc., as well as 
the purine bases, cystine, and possibly other compounds. Since ni- 
trogen compounds other than proteins existing in the original ma- 
terial and susceptible to decomposition with hot acid, would have 
been already broken up in the processing, it follows that the changes 
produced by further boihng with acid would result from peptones, 
proteoses, etc. The difference noted between the results obtained 
from the two extracts for the diamino acids are therefore due to 
some interferring substances of the nature of proteins and not to 
such substances as the purines or cystine. Moreover, the latter com- 
pounds will produce the same relative error in analysis in the case 
of both extracts. 
Of the diamino acids the only one determined directly is arginine. 
Its determination depends on the fact that when arginine is boiled 
for some time with strong potassium hydroxide, half of the nitrogen 
of the arginine is spUt off as ammonia. However, if cystine is present 
18 per cent of its nitrogen is evolved as ammonia, together with the 
arginine nitrogen. As has already been stated this figure should be 
the same for the two extracts providing that there is present in the 
base goods no substance precipitated by phosphotungstic acid, and 
giving off ammonia when boiled with strong alkaU or strong hydro- 
chloric acid. A comparison of the results obtained for arginine in 
the two extracts shows that the figure for arginine in the water ex- 
tract is higher than that of the hydrochloric acid extract by 0.43. 
In other words, there appear to be present in the diamino acid frac- 
tion compounds which on boihng with alkah give off ammonia 
amounting to 0.22 per cent of the total nitrogen. These compounds 
are broken up by the further hydrolysis with acid. 
Further information may be obtained by a consideration of the 
figures for lysine and histidine, which are obtained not by a direct 
determination, but by calculation from the figures obtained for argin- 
ine N, total N in the fraction, amino N and non-amino N. Lysine 
contains only amino N, histidine contains one-third amino N and two- 
thirds non-amino N, while arginine contains one-fourth amino N 
and three-fourths non-amino N. Since histidine N is in a measure 
