1260 



URIC ACID. 



alkalis themselves ; ammonia however scarcely dissolves it, and 

 in this respect it differs conveniently from cystine. It is fairly 

 soluble in glycerin, and soluble to some extent in solutions of 

 lithium carbonate. 



Salts of uric acid. Of these the most important are the acid 

 urates of sodium, potassium and ammonium; these salts are 

 frequently still called 'lithates,' the term 'lithic ' acid being 

 used for uric acid. The sodium salt which is the most common 

 constituent of many urinary sediments crystallizes in many 

 different forms, these not being characteristic, since they are 

 almost the same for the corresponding compounds of the other 

 two bases. It is very sparingly soluble in cold water (1 in 1100 

 or 1200), more soluble in hot (1 in 125). It is the principal 

 constituent of several forms of urinary sediment, and composes 

 a large part of many calculi ; the excrement of snakes contains 

 it largely. The potassium resembles the sodium salt very 

 closely, as also does the compound with ammonium; the latter 

 occurs generally in the sediment from alkaline urine. 



FIG. 214. (Krukenberg after Kiihne.) 



Urinary sediment from alkaline urine. The large crystals consist of ammo- 

 nio-magnesium phosphate (triple phosphate, NH 4 MgPO 4 + 6H 2 O). A few crys- 

 tals (octahedra) of calcium oxalate are also shown. The remaining crystals 

 represent the form of acid ammonium urate, C5H 3 (NH4)N 4 3 . The rounded 

 objects are urinary fungi. 



The amount of uric acid in mammalian urine is too small 

 to make it a source of the acid. Crystals may however be 

 readily obtained from human urine by adding to it 2 3 p.c. 

 of strong hydrochloric acid and letting it stand for one or two 

 days in a cool place. The crystals form on the sides of the 

 containing vessel. 



On the large scale it is usually prepared from guano, or 

 from snake's or fowl's excrement. 



