THE NITBOGEN OF PKOCESSED FERTILIZERS. 5 



was found to be that magnesia under such conditions changes a part 

 of the amino nitrogen of cystine into ammonia. In this laboratory- 

 it was also found that by boiling cystine with lead oxide one of the 

 amino nitrogen groups of this compound was split off almost quanti- 

 tatively, with the concurrent splitting off of hydrogen sulphide. 

 Furthermore, it has been shown that if the amide nitrogen from 

 protein hydrolysis is determined by distillation with a weak alkali, 

 such as calcium hydroxide, at a temperature not to exceed 40° to 

 42° C. in the bath and at a pressure of from 10 to 12 millimeters, 

 no decomposition of cystine takes place. 1 



In the manufacture of base goods the hair which is used contains 

 proteins which on acid hydrolysis yield a high percentage of cystine. 

 This fact, together with the analytical results just discussed, suggest 

 rather strongly that there is present in the base goods more or less 

 cystine, although this evidence can not be considered conclusive, 

 since it is possible that in such a heterogeneous mixture there may 

 be present other nitrogenous compounds which would be decomposed 

 by magnesia or litharge with the liberation of ammonia. 



NITROGEN PARTITION. 



For the purpose of determining the different forms of nitrogen 

 present in the base goods the method of Van Slyke 2 was followed 

 in its essential details, except that the determination of cystine, 

 was not made. The method for the determination of this compound, 

 according to the procedure used by Van Slyke, depends not upon a 

 nitrogen determination but upon the determination of the amount 

 of sulphur in the compounds precipitated by phosphotungstic acid. 

 This determination when made on the hydrolytic products of acid 

 digestion of pure protein may give quite satisfactory results, but the 

 raw materials from which base goods are made contain many organic 

 compounds other than proteins or protein decomposition products, 

 and this is of course particularly true in the case of garbage tankage. 

 It is well known that many plant and animal substances contain 

 sulphur in a variety of linkages, and garbage tankage no doubt con- 

 tains sulphur in other forms than that of cystine. The hair and 

 leather used have both undergone some decomposition before the 

 acid treatment and it is not impossible that the cystine originally 

 present in the proteins may have been changed into sulphur com- 

 pounds of a different chemical nature. No doubt some sulphur com- 

 pounds other than cystine are precipitated by phosphotungstic acid, 

 so that a determination of cystine depending on the sulphur content 

 of the phosphotungstic acid precipitate would be of uncertain value 

 in dealing with material of unknown origin and of such a hetero- 

 geneous character as fertilizer goods. 



i Giimbel, Hofmeister's Beitriige, 5, 297 (1904). > J. Biol. Chem., 10, 15-55 (1911). 



