RELATION BETWEEN CREATIN AND CREATININ 123 



method for the determination of creatinin. JafF e ? s reaction, 

 with its bright red color produced by the addition of sodium 

 hydrate and picric acid to creatinin, is made use of in the 

 method for colorimetric determination. Creatin may like- 

 wise be estimated after complete transformation into crea- 

 tinin by chemical agents (as by the process of Benedict 

 and Meyers 2 by heating the creatin with hydrochloric acid in 

 an autoclave). 3 It would unquestionably be very desirable 

 to discover a direct method of satisfactorily estimating 

 creatin. Whether the proposal to utilize the orange color 

 which diacetyl 4 (CH 3 .CO.CO.CH 3 ) strikes with creatin (but 

 not with creatinin) will prove successful for colorimetric 

 determination remains to be seen ; the results reported are 

 apparently not entirely equivalent to those obtained by 

 Folin's method. 



Relation Between Creatin and Creatinin. Solution of 

 the creatin problem 5 has been retarded by the fact that 



/ N(CH,)-CH, \ 



physiological relation between creatin i c(NH)/ I 



V NH, COOH/ 



(N(CH,) CHA 

 C(NH)/ ) , has 



NH CO/ 



been repeatedly denied. It is, of course, proper to assign no 

 particularly important place in physiological chemistry to 

 "feelings"; but to say the least we cannot well do entirely 

 without them. In the author's judgment a discerning bio- 

 chemical sense must necessarily tell us that two substances, 

 like creatin and creatinin, one of which may be transformed 



2 F. G. Benedict and V. C. Meyers (Wesleyan Univ.), Amer. Jour, of 

 Physiol., 18, 397, 1907. 



1 In the presence of sugar, where the method is attended with certain 

 difficulties, according to W. C. Rose (Univ. of Pennsylvania), Jour, of Biol. 

 Chem., 12, 73, 1912, the creatin may be changed into creatinin by heating with 

 phosphoric acid in the autoclave. 



*G. S. Walpole (Wellcome Research Lab.), Jour, of Physiol., 42, 301, 1911. 



6 Literature upon Creatin Metabolism: C. A. Pekelharing, Centralbl. f. 

 Stoffwechaelkr., 1909, No. 8 ; A. Schittenhelm, Handb. d. Biochem., 4', 535-539, 

 1910. 



