318 APPENDIX. 



nitric acid, a large quantity of nitrate of urea. It had 

 previously deposited a powder, the solution of which in 

 nitric acid gave, when evaporated to dryness, the well- 

 known purple color characteristic of uric acid. This ob- 

 servation is opposed to the statement of Ure ; and he is 

 certainly too hasty in recommending benzoic acid as a 

 remedy for the gouty and calculous concretions of uric 

 acid. He seems to suppose that the uric acid has been 

 employed in the conversion of benzoic acid into hippuric 

 acid ; but as his observation^ were made on a gouty pa- 

 tient, it may be supposed that the urine, even without the 

 internal use of benzoic acid, would have been found to 

 contain no uric acid. Finally, it is clear that the hippuric 

 acid existed in the urine in combination with a base, be- 

 cause it only separated after the addition of an acid. 



In the London, Edinburgh, and Dublin Philosophical 

 Magazine, for June, 1842, is a paper by Mr. Garrod, con- 

 firming Dr. Ure's fundamental observation. When from 

 a scruple to half a drachm of benzoic acid was swallowed, 

 a copious crop of crystals of hippuric acid was obtained, 

 amounting to from fifteen to twenty-nine grains, by the 

 addition of hydrochloric acid to the urine passed three or 

 four hours afterwards. Mr. Garrod states, that he was 

 always able to obtain a distinct trace of uric acid from a 

 drop or two of the urine. 



