URIC ACID. 



479 



duced into a flask having a capacity of about 200 cu. cm., with 20 cu. cm. of 

 pure English sulphuric acid (to one liter of which 200 grams of phosphoric anhydrid 

 are added) , and one drop of metallic mercury ; and this is boiled over the sand- 

 bath until the fluid, which at first was dark, is entirely decolorized. On cooling, 

 the fluid is rinsed with about 200 cu. cm. of water into a flask 

 having a capacity of half a liter, and 100 cu. cm. of sodium hy- 

 drate (of a sp. gr. of 1.34), a few cu. cm. of an aqueous solution 

 of potassium sulphid, and some powdered zinc are added. The 

 flask is then quickly closed with a stopper and the ammonia set 

 free is distilled into a receiver containing 50 cu. cm. of one- 

 tenth normal sulphuric acid. The extremity of the tube from 

 which the ammonia escapes must be immersed in the normal 

 sulphuric acid. In order to determine whether all of the am- 

 monia is present in the receiver, the stopper of the receiver is 

 cautiously removed, a strip of litmus-paper is placed by means 

 of a pair of forceps in front of the tube conveying the ammonia. . 



and note is made whether the escaping distillate causes the strip 

 to turn blue. The amount of sulphuric acid in the receiver not 

 saturated by ammonia is determined by titration with one-tenth 

 normal sodium hydrate. 



According to Pfliiger and Bohland, the amount of nitrogen 

 in the urine can be estimated approximately by the following 

 simple method: To 10 cu. cm. of urine, Liebig's urea-titrating 

 solution is added from a buret, and the mixture is tested upon 

 a dark glass plate with sodium bicarbonate drop by drop, as in 

 the estimation of urea. If the stirred stain remains yellow, the 

 number of cubic centimeters of titration-fluid employed is mul- 

 tiplied by 0.04 and in this way the percentage of nitrogen present 

 is obtained. The total amount of nitrogen in the urine is to the 

 nitrogen in the urea approximately as 5 to 4. 



FIG. 147. Gradu- 

 ated Pi pet. 



URIC ACID C 5 H 4 N 4 3 . 



Next to urea, the greatest amount of nitrogen is 

 eliminated as uric acid, namely, 0.5 gram in 24 hours 

 (in the state of hunger, 0.24 gram ; after a generous meat- 

 diet, 2. ii grams). The amount of uric acid is to that of 

 urea on the average as i to 46, though with many varia- 

 tions. In the mammalian body the uric acid is formed 

 from the nuclein of the disintegrating leukocytes. With 

 increase in the latter, there is increase in the amount of 

 uric acid formed. Ingestion of nuclein as, for instance, after the eating 

 of thymus gland increases the number of leukocytes in the blood and 

 the excretion of uric acid. Xanthin-bases (guanin, xanthin, hypoxan- 

 thin) occur in the intestines as products of the digestion of nucleins. If 

 they be increased in amount, an increase in the amount of uric acid 

 results. 



In birds, reptiles and insects, uric acid is the principal nitrogenous excrementi- 

 tious product; while it appears in but small amount in the urine of herbivora. 



The products of the decomposition of leukocytes present in surviving splenic 

 pulp (nuclein) yield, when treated with fresh blood at the temperature of the 

 body, an abundance of uric acid, together with xanthin and hypoxanthin. Also 

 the nuclein of the nuclei of many other tissues has also shown itself to be a source 

 of uric acid. In addition to uric acid, xanthin-bodies are formed in the same 

 way. When animals are fed with nucleinic acid and hypoxanthin, the elimination 

 of uric acid is increased. 



Uric acid fed to mammals passes into the urine in part further oxidized into 

 urea, together with an increase in the amount of oxalic acid. In hens there is 

 increased elimination of uric acid after the administration of leucin, glycin, 

 aspartic acid, hypoxanthin, or ammonium carbonate. The urea administered to 

 hens is, however, eliminated chiefly reduced to uric acid. 



