URIC ACID. 31 



This is the blue precipitate thrown down from a solution of 

 protoxide of iron by the red prussiate. 



1. Sulphocyanogen, C 2 Az + S 2 = 7*75. 



2. Sulphocyanhydricacid, (C 2 Az + S 2 ) + H = 7-875. 



3. Sulphocyanet of ammonium, (C 2 Az + S 2 ) + Az H 4 = 10. 



4. Sulphocyanet of potassium, (C 2 Az H- S 2 ) K = 12-75. 



5. Sulphocyanet of lead, (C 2 Az + S 2 ) + Pb = 20-75. 



6. Basic sulphocyanet of lead, (C 2 Az -f- S 2 ) + Pb + PbO - 



34-75. 



7. Sulphocyanet of mercury, (C 2 Az -f S 2 ) + Hg = 20-25. 



SECTION II. OF URIC ACID. 



This very important substance was discovered, and its charac- 

 ters ascertained by Scheele, in 1776.f He found it in urinary 

 calculi ; and all the calculi examined by him consisted of it. 

 From the properties of it pointed out by Scheele, it was consi- 

 dered as an acid, and Morveau gave it the name of lit hie acid. { 

 The experiments of Scheele were confirmed by those of Berg- 

 man, and of Fourcroy and Vauquelin during their examination 

 of urinary calculi. || In 1798, a long paper on urinary calculi 

 by Dr Pearson was inserted in the Philosophical Transactions.^! 

 It contained little that had not been already determined by 

 Scheele. But Pearson affirmed that the characters of the lithic 

 acid of Scheele were not those of an acid. He called it an oxide, 

 and the term lithic being in his opinion improper, he distinguished 

 it by the name of uric oxide ; a term which he had already em- 

 ployed in his translation of the French Chemical Nomenclature.** 

 Fourcroy, admitting the impropriety of the name lithic, but still 

 maintaining that the substance was an acid, gave it the name of 

 uric acid, which was generally adopted. ff 



Brugnatelli made some experiments on this acid, one of which 



* Inorganic Chemistry, ii. 241. 



f Kougl. Vet. Acad. Handbl. 1.776, p. 327 ; or Scheele's Chemical Essays, 

 p. 199. 



\ EneycL Meth. Chemic Art. Acides ; or Lavoisier's Traite de Cbimie, 

 p. 318. 



Kong. -Vet. Acad. Handl. 1776, p. 333. 



|| Ann. de Chim. xvi. 63, and xxvii. 225. 



f Phil. Trans. 1798, p. 15. 

 ** See the last table in that work. ft Ann. de Chim. xxvii. 286. 



