239 



hours, mentioned by him, as the period of spontaneous 

 separation, is by far, in the healthy state, too short, and 

 that it extends to two, three, and, sometimes, more days, 

 according to the existing temperature, and other circum- 

 stances. Nothing, therefore, I will presume to say, is 

 more erroneous, than the assertion, repeated in almost 

 every chemical book, that the uric acid separates from 

 urine, upon cooling. When this occurs, which frequently 

 happens, particularly with children, the urine is certainly 

 surcharged with this A'ery insoluble substance. 



An increased temperature hastens the incipient decom- 

 position of urine; and its first ammoniacal degeneration is 

 always attended by the deposition of its uric acid, in its 

 crj'^stalline form. 



This did not escape the observation of Hales, who tells 

 us, that urine, tending to putrefaction, aifords most of this 

 acid substance: and, indeed, were it to be deposited upon 

 cooling, or Avithin the space of twenty-four hours, or even 

 more, as is so generally asserted, it should, every day, 

 present itself to physicians, who so constantly attend to 

 the state of urine in glasses; but this is by no means the 

 case: and we find Fourcroy, in his last publication, men- 

 tioning from twenty-four to forty-eight hours, which cer- 

 tainly only applies to summer heat, or the circumstance 

 already mentioned. 



Our next great obligation is, undoubtedly, to Scheele; 

 who has made us acquainted with its nature, and the 

 very distinct chemical properties already enumerated. 



II h 2 While 



