BLOOD ANALYSIS 



283 



i c.c. of 10 per cent sulphite solution; 3 c.c. of 20 per cent sodium carbonate, 2 c.c. 

 of the acidified sodium chloride, 0.5 c.c. of the sodium cyanide solution, and 25 

 c.c. of the weaker one of the two regular standard solutions already on hand. 

 Dilute to 50 c.c. and mix. Or, simply add 5 c.c. of 20 per cent sodium carbonate 

 to 25 c.c. of the regular weaker standard, and dilute to 50 c.c. 



If a low uric acid value is expected, an alternate procedure is to dilute the un- 

 known to a final volume of 10 c.c. with corresponding reduction in the amount 

 .of the reagents used. 



Special attention should perhaps be called to one small 

 yet essential variation in the process for developing the 

 blue uric acid color, a variation made necessary by the 

 use of sodium sulphite. The uric acid reagent must 

 invariably be added after, and not before, the addition of 

 the sodium carbonate, because in acid solution the sulphite 

 will itself give a blue color with phosphotungstic acid. 



25 cc. 



Interpretation. Normal human blood usually 

 contains from 2-3 mg. of uric acid per 100 c.c. 

 In early interstitial nephritis values of from 3-10 

 mg. are noted. Uric acid increases in the bkfod 

 in this condition sooner than urea or creatinine, 

 probably because it is less soluble and less readily 

 excreted by the kidneys. The determination of 

 uric acid is, therefore, of especial value in early 

 nephritis. In severe nephritis values up to 25 

 mg. may be obtained. 



In gout high uric acid values (4-10 mg.) are 

 usually found. Determination of uric acid, there- 

 fore, is of value in the diagnosis of gouty arthritis 

 prior to the stage of tophi formation. It must 

 be borne in mind, however, that uric acid is 

 similarly increased in early nephritis and that 

 many cases of gout showing high uric acid values 

 also show defective kidney function by other 

 tests. The same difficulty is met with in con- (Folhnd Wu: 

 sidering the high values (2-8 mg.) obtained in Biol. Chem., March, 

 other arthritis conditions, usually associated with 

 increases in urea also. The existence of nephritis in such cases has 

 not been entirely excluded and many typical cases of arthritis show 

 values below 3 mg. 1 Salicylates and atophan tend to reduce the uric 

 acid content of the blood. 



7. Determination of Sugar. Principle. The protein-free blood 

 nitrate is heated with alkaline copper solution, using a special tube 

 to prevent reoxidation. The cuprous oxide formed is treated with a 



1 See Myers: "Practical Chemical Analysis of Blood," St. Louis, 1921. 



t 8mm. 



4cc. 



(Not Marked) 



FIG- 89. FOLIN-WU 



