16 BULLETIN 158, U. S. DEPARTMENT OF AGRICULTURE. 



There is an increase of 0.47 per cent amide X in the hydrochloric 

 acid extract over that in the water extract. This is due to the 

 splitting 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, histidine, 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 boiling 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 deterrnination depends on the fact that when arginine is boiled 

 for some time with strong potassium hydroxide, half of the nitrogen 

 of the arginine is split 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 alkali 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 boiling with alkali 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 X. Lysine 

 contains only amino X, histidine contains one-third amino X and two- 

 thirds non-amino X, while arginine contains one-fourth amino X 

 and three-fourths non-amino X. Since histidine X is in a measure 



