352 Dr. Prout on &pme of the [May, 



r 2j.Lfr4- — = - x — + A- ; this correction being made, 



•* ~ 5 25 « 9 75 ' ° 



a / 25 m + Sn a a / m c* + 3 n a 



we have * = — ^/ 5 ~ si y/ « 7 * 



the same as before, s 2 = -L and c = 5. 



Here 1 = AG, the breadth at the tap of the wall. 



Article VIII. 



Observations on the Nature of some of the Proximate Principles 

 of the Urine; with a few Remarks upon the Means of prevent- 

 ing those Diseases, connected with a morbid State of that 

 Fhiid. By William Prout, M.D * 



The substances to which the author proposes to confine his 

 attention in this paper are, urea, saccharine matter, and lithic 

 acid ; the other constituents of the urine are omitted for the 

 present, in consequence of the uncertainty which prevails 

 respecting them. 



The urea was obtained in a separate, although in a very impure 

 state, by Rouelle, in 1773, and styled the saponaceous extract 

 of urine. It was made the subject of particular examination by 

 Cruickshanks, and shortly after by Fourcroy and Vauquelin, who 

 first gave it the name of uree ; but although they made us 

 acquainted with many of its leading properties, it was not ob- 

 tained by them in a perfectly pure state. This seems to have 

 been first accomplished by Berzelius, judging from the descrip- 

 tion which he gives us of its physical and chemical properties ; 

 but he does not give us any account of the process which he 

 employed. M. Thenard, in his late work, describes it in such 

 a manner as to show that he had procured it in a somewhat 

 purer state than Cruickshanks ; but still it seems not to have 

 been entirely so, as it retained a urinous odour, and deli- 

 quesced, on exposure to the atmosphere. 



The process which Dr. Prout employs, is as follows. To the 

 extract of urine evaporated to the consistence of a syrup, nitric 

 acid is to be gradually added until the whole is converted to a 

 crystalline mass, which is to be slightly washed with cold water. 

 The nitric acid is then neutralized by a solution of subcarbonate 

 of potash, or soda, and the solution evaporated, in order that the 

 nitrate of potash or soda may crystallize, and be thus separated. 

 The fluid which is left is made into a paste with animal charcoal; 

 cold water separates the urea from this paste in a colourless 

 state ; it is to be evaporated to dryness, and the mass digested 



» Abridged from the eighth volume of the Med. Chir. Trans. 



