92 METHODS FOR THE ANALYSIS OF BLOOD 



DETERMINATION OF CREATINE PLUS CREATININE 



Principle. The principle is the same as that employed in the 

 determination of creatine in the urine. 



Procedure. Transfer 5 c.c. of blood filtrate to a test-tube 

 graduated at 25 c.c. These test-tubes are also used for urea and 

 for sugar determinations. Add 1 c.c. of normal hydrochloric acid. 

 Cover the mouth of the test-tube with tin-foil and heat in the 

 autoclave to 130 C., for twenty minutes, or, as for the urea 

 hydrolysis to 155 C., for ten minutes. Cool. Add 5 c.c. of the 

 alkaline picrate solution and let stand for eight to ten minutes, 

 then dilute to 25 c.c. The standard solution required is 20 c.c. of 

 creatinine solution in a 50 c.c. volumetric flask. Add 2 c.c. of 

 normal acid and 10 c.c. of the alkaline picrate solution and after 

 ten minutes standing dilute to 50 c.c. The preparation of the 

 standard must, of course, have been made first so that is it ready 

 for use when the unknown is ready for the color comparison. The 

 height of the standard, usually 20 mm., divided by the reading of 

 the unknown and multiplied by 12 gives the " total creatinine " 

 in mg. per 100 c.c. of blood. 



In the case of uremic bloods containing large amounts of 

 creatinine 1, 2, or 3 c.c. of blood filtrate, plus water enough to make 

 approximately 5 c.c. are substituted for 5 c.c. of undiluted filtrate. 



The normal value for " total creatinine " given by this method 

 is about 6 mg. per 100 c.c. of blood. 



DETERMINATION OF URIC ACID 



Principle. Uric acid is separated from the blood filtrate as the 

 silver salt. The silver urate is then dissolved by means of alkaline 

 sodium cyanide solution. By means of a uric acid reagent a color 

 is developed the depth of which is compared to a standard solution 

 of uric acid to which has been added the uric acid reagent. 



Solutions Required for Uric Acid Determinations. 1. Standard 

 uric acid sulphite solution prepared as follows : Make 1 to 3 liters 

 of a 20 per cent solution of sodium sulphite, let stand over night, 

 and filter. Dissolve 1 gm. of uric acid in 125 to 150 c.c. of 0.4 per 

 cent lithium carbonate solution, and dilute to a volume of 500 c.c. 

 Transfer 50 c.c., corresponding to 100 mg. of uric acid, to each of 



