URIC ACID. 55 



cular crystals, or else separates in granules or scales. It dissolves 

 in 140 parts of cold, and in 85 parts of boiling water. 



Urate of soda may be obtained in a similar manner, or by 

 boiling uric acid in a solution of borax. It is far less soluble 

 tlian the former salt ; one part of it requiring for its solution 

 372 parts of cold, and 124 parts of boiling water. In other 

 respects it closely resembles it. It occasionally constitutes a 

 very peculiar stellar form of deposit in the urine. Liebig has 

 shown that uric acid dissolves with great facility in a solution 

 of common phosphate of soda, that the fluid from being al- 

 kaline becomes acid, and that there are formed a urate of soda, 

 and an acid phosphate of soda. It is in this condition that he 

 supposes uric acid to exist in the urine. 



Urate of ammonia, in a state of piu'ity, invariably crystallizes 

 in needles, but if a httle chloride of sodium be added to its so- 

 lution we no longer obtain, on evaporation, a crystalline acicular 

 deposit, but the peculiar amorphous form in which urate of am- 

 monia occurs in mine. On the addition of chloride of sodium 

 to water, in the proportion of 2' 59 to 1000, the solubility of 

 urate of ammonia is increased in the proportion of 1000 to 450, 

 or is more than doubled. (Dr. Bence Jones, in Trans, of the 

 Medico-chirurgical Society, 1844.) 



According to Liebig, this salt requires for its solution 1727 

 parts of cold, and 243 parts of boiling water. 



Urate of magnesia may be obtained by the addition of sul- 

 phate of magnesia to a boiling saturated solution of urate of 

 potash. On cooling, and after the fluid has been allowed to 

 stand for some time, urate of magnesia is deposited in fine 

 needles of a silky lustre, and arrayed in stellar groups. At 

 212^ these crystals lose 5 atoms of water. Urate of magnesia 

 dissolves in 3593 parts of cold, and 263 parts of boiling water. 



Urate of lime forms white glittering needles or leaves, which 

 dissolve pretty readily in hot water, but are thrown down again 

 on cooling. 



Diagnosis of uric acid. Uric acid is distinguished by the 

 form of its crystals under the microscope, by its insolubility in 

 water and in alcohol, and by its behaviour toAvards nitric acid 

 and ammonia. 



The Metamorphoses of Uric Acid. Allantoin. One part 

 of uric acid is boiled in 20 parts of water, and freshly prepared 



