48 METHODS FOR THE ANALYSIS OF URINE 



less than 7 mg. of total creatinine use a correspondingly smaller 

 or larger volume of urine.) Add from 10 to 20 c.c. of normal 

 HC1, and a pinch or two of powdered or granulated lead. Boil 

 the mixture over a free flame as slowly or as rapidly as may be 

 desired, until very nearly down to dryness, when the heating 

 should be continued to dryness either on the water-bath or very 

 easily by simply holding the vessel in the hand and heating care- 

 fully for a moment or two. Let the residue stand on the water- 

 bath for a few minutes until most of the excess of hydrochloric 

 acid gas has been expelled, after which dissolve it in about 10 c.c. 

 of hot water and rinse the solution quantitatively through a plug 

 of cotton or glass wool (to remove all metallic lead) into a 500 c.c. 

 volumetric flask. Add 20 to 25 c.c. of a saturated picric acid solu- 

 tion and about 7 to 8 c.c. of a 10 per cent NaOH solution, which 

 contains 5 per cent of Rochelle salt. At the end of five minutes 

 fill to the mark with water and read in the colorimeter just as 

 in the case of creatinine. 



Calculation. Calculate the creatinine content of the solu- 

 tion in the same manner as given under Creatinine. From the 

 value thus obtained subtract the value for the creatinine content 

 of the urine before dehydration. The difference will be the 

 creatine content of the original urine in terms of creatinine. 



CREATINE 



Microchemical Modification of Folin 1 



Principle. By greatly diluting the urine the time required 

 for the conversion of creatine to creatinine is decreased, and 

 picric acid can be substituted for mineral acid. 



Procedure. Enough urine to give 0.7 to 1.5 mg. of creatinine 

 is measured into a weighed Erlenmeyer Jena flask (capacity 200 

 c.c.); 20 c.c. of saturated picric acid solution, about 130 c.c. of 

 water, and a few very small pebbles to promote even boiling 

 are added and the mixture is gently boiled, preferably over a 

 micro-burner for about one hour. At the end of this time the 

 heat is increased and the solution is boiled down to rather less 

 than 20 c.c. The flask is transferred to the scales and enough 

 water is added to make the total solution equal to 20 to 25 gms. 

 1 Folin: Jour. Biol. Chem., 1914, 17, 469. 



