266 Suggcstions to Teachers of Biochemistry [Dec. 



pronounced blue color to the alkaline Solution, some of the liquid 

 was added to a dilute Solution of tgg white. A beautiful biuret 

 reaction was instantly obtained "di^ith a single drop of the reagent in 

 about 10 c.c. of the protein fluid. 



Dozens of similar tests immediately afterward, from many 

 Standpoints, made it very evident that the coppered caustic alkali 

 Solution would meet every ordinary expectation as a biuret reagent, 

 It yielded sharper tinctorial effects than any obtainable by the 

 classical method of applying the biuret test, and exceptional econ- 

 omy of all necessary materials was assured by its employment. 

 After ascertaining that the blue color in the coppered caustic 

 alkali Solution was not due to a finely divided Suspension, we feit 

 that the last objection to the selection of 4 oz, bottles as our reagent 

 Containers had disappeared, and to each set of 32 bottles was added 

 one bottle labeled "BIURET REAGENT." 



The routine use of the biuret reagent was inaugurated in our 

 laboratory of physiological chemistry at Teachers College in the fall 

 of 1909. Its employment there and in the other laboratories of the 

 department has been proceeding continuously, with perfect satis- 

 faction. Two years ago the senior author published a preliminary 

 Statement regarding the Utility of his reagent.^ Its continued use in 

 the laboratories of this department has emphasized both the prac- 

 tical and the scientific value of the biuret reagent from every point 

 of view. 



During the summer of 1910 the junior author cooperated in a de- 

 tailed study of the biuret reagent from a number of practical stand- 

 points, especially with regard to the influence of substances and con- 

 ditions which occur in connection with every day applications of the 

 biuret test. A preliminary report of some of the results has already 

 been published.^ Our findings made it evident that the biuret 

 reagent affords, in general, a more effective means of applying the 

 biuret test than any other hitherto described. The employment of 

 the biuret reagent saves time, economizes material, prevents the 

 introduction of an excess of copper, affords a satisfactory color 



'Gies: Proceedings of the American Society of Biological Chemists, 1910, 

 j> P- 273 ; Journal of Biological Chemistry, 1910, vii, p. Ix. 



* Kantor and Gies : Proceedings of the American Society of Biological 

 Chemists, 1911, ii, p. 11; Journal of Biological Chemistry, 1911, ix, p. xvii. 



