1890.] 



A Cyanogen Reaction of Proteids. 



207 



Coagulated proteid behaves like the peptones ; this is easily 

 explicable, as Neumeister* has shown that the action of hot water cn 

 proteids forms from them small quantities of albumoses due to 

 hydration. The other proteids in the above list behave like the 

 albumins, and thus differ from the albumoses and peptones. 



I now pass from the proteids to certain derivatives of proteids, 

 these experiments being designed to elucidate the question as to what 

 radicle it is on the proteid molecule to which these reactions are 

 due. 



Uric Acid — Uric acid was dissolved in soda and boiled; then 

 cooled, and a drop of copper sulphate added ; this did not colour the 

 fluid at all ; on adding more, a violet solution was obtained. f 



Uric acid dissolved in soda, but not heated, gave with cupric 

 hydroxide in ammonia a pink colour. 



A little uric acid was evaporated to dryness on a porcelain dish 

 with nitric acid ; on adding cupric hydroxide in ammonia to this a 

 violet colour is obtained; this is not simply the murexide test pro- 

 duced by the ammonia, as nickel oxide dissolved in ammonia gives a 

 deep yellow colour. Thus uric acid gives the reactions very much as 

 proteids do. 



Xanthine, hypoxanthine, and sarcosine give the same reactions. 



Biuret and cyanuric acid are the substances in which the colour 

 tests with cupric hydroxide in alkaline solutions were first observed ; 

 the following are the particulars of the experiments I have performed 

 with these two substances : — 



Addition of — 



To aqueous solution of 

 biuret. 



To aqueous solution of 

 cyanuric acid. 



(1.) Cupric sulphate. 

 (2.) Cupric sulphate and 



potash. 

 (3.) Cupric sulphate and 



ammonia. 

 (4.) Cupric sulphate and 



ammonia, followed 



by potash. 

 (5.) Nickel sulphate dis- 

 solved in ammonia. 

 (6.) Nickel sulphate in 



ammonia, followed 



by potash. 



No effect. 

 Rose-red solution. 



Blue solution. 



Rose-red solution. 



Blue solution. 



Orange solution (with 

 flocculent precipitate) . 



No effect. 

 Yiolet solution. 



Blue solution. 



Yiolet solution. 



Blue solution. 



Yellow solution (with 

 flocculent precipitate) 



* 'Zeitsch. f. Biol.,' vol. 24, p. 272. 



f Winogradoff (' Yirchow's Archiv,' vol. 27, p. 565) and Worm-Muller (' Pfhiger's 

 Archiv,' vol. 27, p. 31) mention something similar, but not in connexion with the 

 present subject. 



VOL. XLVH. R 



