CREATININEJ 47 



tap water and the color of the unknown is determined. The read- 

 ing of the standard divided by the reading of the unknown gives 

 directly the number of milligrams of creatinine in the amount 

 of urine taken for analysis. 



CREATININE 



Shaffer's Modification for the Determination of Creatinine 

 in Very Dilute Solutions 1 



The regular Folin procedure is not accurate when applied to 

 urines containing less than 20 mg. of creatinine per 100 c.c. By 

 a slight modification it becomes applicable to creatinine solutions 

 containing as little as 1 mg. or less per 100 c.c. 



Procedure. To the solution under examination add an equal 

 volume of saturated picric acid solution and one-tenth this volume 

 of 10 per cent sodium hydroxide solution. After standing six 

 to ten minutes the liquid is diluted to a definite volume depending 

 upon the intensity of the color developed. With very dilute 

 solutions one may add solid picric acid equivalent to half satu- 

 ration (0.6 per cent) and when dissolved, one-twentieth the 

 volume of sodium hydroxide. Provided the creatinine solution 

 itself has not sufficient color to interfere, the results by this 

 method appear to be as accurate as the original procedure. The 

 colorimetric readings and calculations are made in the same 

 way as in the preceding methods. 



CREATINE 



Folin-Benedict Method 2 



Principle. Creatine on boiling with acid is transformed into 

 creatinine. By determining the content of creatinine before 

 and after the acid treatment we are able to calculate the amount 

 of creatine originally present in the urine. The Folin colori- 

 metric method is used for determining the creatinine in both 

 cases. The method is not applicable to diabetic urines. 



Procedure. Introduce into a small flask or beaker 10 c.c. 

 of the urine to be examined. (If 10 c.c. contains more than 12 or 

 Chaffer: Jour. Biol. Chem., 1914, 18, 525. 

 * Benedict: Jour. Biol. Chem., 1914, 18, 191. 



