124 THE HOLE UF NITROGEN IN PLANT-METABOLISM, 111., 



ammonia. Krviger and Schmid* heated amino-acids with 

 concentrated sulphuric acid at 160° C, and showed that no 

 ammonia was given off on distillation with alkali. Now 2 

 and 3 show that the nitrogen is obtained from compounds 

 which are rapidly decomposed by hydrolysis, and 4 that, 

 after removal of basic compounds, the hydrolysis and distil- 

 lation remove these readily decomposable compounds almost 

 entirely. We can, then, only conclude from the above that 

 amino-acids are not present, or exist in very small amounts 

 (See 4) in the non-protein nitrogen solution. This conclu- 

 sion is confirmed also by the formaldehyde titration. 



This slow decomposition, with formation of ammonia, is 

 characteristic of certain groups of organic compounds. 

 Erdmann f has shown that compounds containing the nitril 

 grouping, when heated with sulphuric acid, form amines, 

 and finally ammonia. 



Embdeni found that cystin gives off ammonia, when boiled 

 for a long time with magnesia ; and Mathews and Walker§ 

 that it oxidised spontaneously in alkaline solutions, setting 

 free ammonia. Neuberg and Mayer|| crystallised cystin in 

 radiating bunches of needles like ty rosin. 



Jollest by slow oxidation of plant-protein, at ordinary 

 temperature, obtained urea 50%, nitrogen in phosphotungstic 

 acid precipitate 20%, and in filtrate 30% of the total nitrogen. 

 The urea originates in the — CONH — and — CONH^ groups 

 of the protein molecule, and is analogous with the breaking 

 down and oxidation of proteins in the organism. 



Plimmer**, by oxidising albumins, obtained hydrocyanic 

 acid, and he states that it arises from the glycin and aspartic 



» Zeit. physiol. Chem 30, 1900, 556. 

 t Ekdmann— Journ. Biol. Chem. 8, 1910, 41. 

 X Embukn— Zeit. physiol. Chem. 32, 1900, 95. 

 § Mathkws & WALKKR-Journ. Biol. Chem. 6, 1909, 289 

 II Nkuberg k Maykr — Zeit. physiol. Chem. 44, 1905, 472. 

 H Joi,LEs-!7)u/. 32, 1900, 361. 

 "* PLIMMER-Jouni. Physiol. 32, 19U4, 51. 



