URINE 511 



again, after which add 10 c.c. of 20 per cent sodium carbonate solution, 1 transfer 

 quantitatively to a 50 c.c. flask, and at the end of about one -half minute, dilute 

 to mark. Compare this solution in the Duboscq colorimeter (page. 486) with a 

 simultaneously prepared solution obtained by treating 5 c.c. of the standard uric 

 acid solution, 2 contained in a 50 c.c. flask, with 2 drops of the potassium cyanide 

 solution, 2 c.c. of the uric acid reagent, 10 c.c. of 20 per cent sodium carbonate solu- 

 tion, and diluting to the mark at the end of about one-half minute. The stand- 

 ard solution is best set at a height of 15 mm. in the colorimeter. 



Calculation. The reading of the standard divided by the reading of the urine 

 gives the number of milligrams of uric acid in the amount of sample taken. 



Interpretation. For adults on a mixed diet the average excretion of 

 uric acid is about 0.7 gram. It arises from the purines of ingested food 

 (exogenous uric acid) and from purines derived from the body tissues 

 by disintegration of nuclein material (endogenous uric acid). Exog- 

 enous uric acid depending entirely upon the diet is greatly increased 

 by the ingestion of purine-rich foods (meat, liver, sweetbreads, etc.) and 

 reduced to a very low level on purine-free foods, e.g., milk, eggs, etc. 

 (see Chapter XXVII) . Endogenous uric acid is influenced by exercise 

 and by the diet (protein foods particularly giving rise to increases). 

 It appears to be partly the result of gastro-intestinal secretory activity. 

 On a purine-free diet the average excretion is 0.1-0.5 gram. On a high 

 purine diet the uric acid output may be 2 grams per day. 



In gout the uric acid content of the urine is low preceding an attack 

 and increases during the attack, this fall and rise being more or less 

 characteristic. The excretion rises after atophan administration ap- 

 parently due to increased kidney activity. In leukemia the excretion 

 is extremely high due to nuclear destruction. The uric acid content 

 of the urine is of importance in relation to the formation of uric acid 

 calculi. The administration of alkali carbonates and citrates by de- 

 creasing the acidity of the urine increases its solvent power for uric 

 acid, and decreases the liability of the formation of this type of calculus. 



3. Folin-Shaffer Method. 3 Principle. The uric acid is precipitated 

 as ammonium urate by the addition of ammonia, the precipitate filtered 

 off, washed and titrated with potassium permanganate. A preliminary 



1 Sodium Carbonate Solution. Dissolve 200 grams of anhydrous sodium carbonate in 

 warm water and make up to i liter. 



2 Standard Uric Acid Solution. The solution of uric acid in phosphate solution is very 

 readily prepared, does not need to be standardized, and appears to keep indefinitely. It is 

 prepared in the following manner. Dissolve 9 grams of pure crystallized disodium hydro- 

 gen phosphate, together with i gram of crystallized sodium dihydrogen phosphate, in 200 

 to 300 c.c. of hot water, and filter if the solution is not perfectly clear. Make this 

 filtrate up to about 500 c.c. with hot water, and pour this hot or warm (and perfectly clear) 

 solution upon exactly 200 mg. of pure uric acid suspended in a few cubic centimeters of 

 water in a liter volumetric flask. Agitate the mixture for a few minutes until the uric acid 

 completely dissolves. Cool, add exactly 1.4 c.c. of glacial acetic acid, dilute to the mark, 

 and mix. Add about 5 c.c. of chloroform to prevent the growth of bacteria or moulds in the 

 solution. Five c.c. of this solution contains exactly i mg. of uric acid. 



3 Folin and Shaffer: Zeit. physiol. Chem., 32, 552, 1901. 



