URINE. 177 



chloric acid. Upon cooling, the uric acid will separate and must 

 be collected. 



c. Increase of urate of soda. I am not certain whether urate 

 of soda exists in normal urine. I shall, however, proceed to 

 state in what manner its presence may be recognized in certain 

 pathological conditions. Deposits of urate of soda alone are 

 not often to be met with; this substance is, however, frequently 

 associated with uric-acid and urate-of-aumionia sediments. 

 Urate of soda is detected chemically in the same manner as 

 urate of ammonia ; like that salt it dissolves on the application 

 of heat ; and when warmed on a porcelain capsule with a little 

 nitric acid, it develops the same purple colour. It differs, how- 

 ever, from that salt, in not developing an odour of ammonia 

 when rubbed with caustic potash, and in leaving a white ad- 

 hesive residue, when heated on platinum foil. This residue 

 when moistened with water, colours red litmus paper blue, and 

 froths when treated with hydrochloric acid, (carbonate of soda.) 

 It may be distinguished in the same manner as the urate of 

 ammonia from uric acid, earthy phosphates, mucus, or pus. 



Under the microscope it presents the form of globules, min- 

 gled with small prisms arranged in stellar groups : at least it is 

 in this form that I have always seen it when obtained artificially; 

 and I have detected such globules, only of^, more opaque 

 appearance, in certain urinary sediments. These forms are 

 exhibited in fig. 29 a and b. Certain forms described by Vigla 

 and Quevenne are given in fig. 29 c. This peculiar crystalline 

 arrangement is sufficiently characteristic to enable the urate of 

 soda to be detected when mixed with urate of ammonia, or other 

 sedimentary matters, either crystalline or amorphous. 



For a quantitative analysis of a sediment consisting of pure 

 unmixed urate of soda we must proceed in exactly the same 

 manner as for urate of ammonia. If, however, it is mixed with 

 uric acid, earthy phosphates, or mucus, the same method must 

 be adopted as for urate of ammonia under similar circumstances, 

 If urate of ammonia is mixed with urate of soda, they are both 

 held in solution when the urine is warmed, and are thus sepa- 

 rated from the other constituents of the sediment. 



The solution is then slightly concentrated by evaporation, and 

 afterwards thoroughly cooled. The alkaline urates separate them- 



ii. 12 



