204 



Dr. J. Gnezda. 



[Feb. 20, 



soda usually employed. In some cases I have added each reagent 

 separately, first copper sulphate, then ammonia, and then potash or 

 soda ; but, as a rule, I have employed a reagent made by dissolving 

 a copper salt in ammonia ; the dark blue solution that results is an 

 ammoniacal solution of cupric hydroxide. After adding this to a 

 solution of proteid and observing the result, potash or soda can be 

 added subsequently. The use of the ammoniacal solution of cupric 

 hydroxide as a reagent for detecting proteids was first suggested to 

 me by the fact that on adding some of it to urine from a case of 

 cystitis I obtained a reddish- violet colour. In the light of subse- 

 quent experiments, it is probable that this urine contained a peptone 

 or peptone-like substance derived from the decomposition of pus 

 corpuscles. , 



The reactions I obtained with various proteids may be thus tabu- 

 lated : — 



Proteids. 



Addition of ammoniacal 

 solution of cupric 

 hydroxide produced : — 



1 



Subsequent addition of 



potassium or sodium 

 hydroxide produced : — 



Egg albumin. 



Serum albumin. 



Grriibler's peptone, 

 j Witte's peptone. 

 I Pure peptone (prepared 

 i from Witte's peptone) . 

 j Albumoses (prepared 

 from Witte's peptone) . 



1 



Pale blue solution. 

 Pale blue solution. 

 Violet solution. 

 Violet solution. 

 Violet solution. 



Violet solution. 



Violet solution. 

 Violet solution. 

 Rose-red solution. 

 Rose-red solution. 

 Rose-red solution. 



Rose-red solution. 



Native albumins differ from the products of proteolysis (albumoses 

 and peptones) by giving no change of colour with an ammoniacal 

 solution of cupric hydroxide ; when potash or soda is subsequently 

 added, the result is, as usual, a violet solution. The albumoses and 

 peptones, on the other hand, give a violet solution -with the ammonia- 

 cal cupric hydroxide ; this is turned red on the subsequent addition of 

 potash or soda. 



Copper sulphate and ammonia added separately give the same 

 results. When a drop of copper sulphate solution is added to a 

 proteid solution, the result is a precipitate of an albuminate of 

 copper;* on adding ammonia, this dissolves up; if the solutionis 

 blue, changing to violet when potash is added, albumoses and pep- 

 tones are absent ; but if the solution is violet, changing to red when 

 potash is added, albumoses or peptones, or both, are present. 



* This preliminary precipitation does not, however, occur with deutero-albumosfc 

 nor with pure peptone. 



