208 



Dr. J. Gnezda. 



[Feb. 20, 



Biuret thus behaves in very much, but not exactly, the same way 

 as peptones ; while cyanuric acid gives the same colour reactions as 

 albumin. 



Hydrocyanic Acid. — The same series of reactions was tried with 

 this substance, and the result was that the colours obtained were 

 precisely the same as those obtained with peptones and albumoses. 



The details are as follows : — 



Addition of Produced 



Cupric sulphate No effect. 



Cupric sulphate and potash Rose-red solution. 



Cupric sulphate and ammonia, or ammoniacal 



solution of cupric hydroxide Yiolet solution. 



Subsequent addition of potash or soda Rose-red solution. 



Nickel sulphate dissolved in ammonia. ..... Yellow solution. 



Subsequent addition of potash or soda Orange solution. 



The colours produced are in some cases evanescent, and, if any free 

 acid is left not neutralised by the ammonia or potash added, the 

 liquid remains colourless. 



Glycocine, Leucine, Tyrosine. — These substances gave negative 

 results, the liquid remaining blue or bluish-green throughout. 



Ethyl aldehyde, propyl aldehyde, valer aldehyde, isobutyl aldehyde, and 

 benzyl aldehyde similarly gave entirely negative results. 



General Conclusions. 



The addition of cupric sulphate and potash to albumin or 

 globulin produces a violet solution. The addition of the same 

 reagents to peptones or albumoses causes a rose-red solution. If 

 ammonia be added as well the results are as follows : — Cupric 

 sulphate and ammonia added to albumin causes a blue solution, 

 turned violet on the addition of potash ; cupric sulphate and ammonia 

 added to peptone or albumose gives a violet solution, turned red on 

 the addition of potash. 



By this reaction, and by a somewhat similar reaction in which 

 nickel sulphate is used, peptones and albumoses may be easily dis- 

 tinguished from, and detected in the presence of, albumins and 

 globulins. 



Not only proteids, but other organic substances ultimately obtain- 

 able from proteids, give very similar reactions. 



The reaction is not given by the amido-acids, glycocine, and 

 leucine ; nor by derivatives, like tyrosine and benzyl aldehyde, that 

 contain an aromatic nucleus, nor by the aldehydes of various alcohols. 

 But in the substances that do give the test, the nitrogen is either 

 partly or wholly combined in the form of cyanogen: these substances 

 are biuret, cyanuric acid, uric acid, xanthine, hypoxanthine, sarco- 



