Chemical Science. 157 



history of this alkaline substance, and the method we have 

 adopted in analyzing the stavesacre." 



Paris, July 12, 1819. Annates de Chini. xi. 188. 



3. On the action of Nitric Acid, Chlorine, and Iodine, on Uric 

 Acid, by M.Vauquelin. — For eight months I have employed all my 

 leisure moments in those researches on the action of nitric acid, 

 chlorine, and iodine, on uric acid, announced by M, Brugnatelli, 

 and repeated by Dr. Prout. To detail here all the experiments 

 I have made on this subject would be too tiresome, but I shall 

 give the principal results of them. I have not been able to 

 gather any thing useful from the memoirs of Messrs. Brugna- 

 telli and Prout ; because, one of these gentlemen has not given 

 the process which he followed for the preparation of what 

 he calls purpuric acid, and what the other has said appears 

 unintelligible to me, and because these chemists contradict 

 each other on a great number of points, respecting the properties 

 of the acid they have discovered. 



I will first observe that uric acid suffers the same changes, 

 and gives the same products, whether it be treated with nitric 

 acid, chlorine, or iodine ; but these products change in their 

 nature according as the action of the agents is continued to a 

 lesser or greater extent. If this action is retarded, a large 

 quantity of a particular colouring matter is formed, and very 

 little acid; if it is carried farther, without passing certain 

 limits, little colouring matter is obtained, but a much larger 

 quantity of acid ; and finally, if the action be continued for a 

 long time, these two substances disappear, and oxalic acid and 

 ammonia only are obtained. Thus in varying the quantity of these 

 bodies, and the manner in which they act on the calculous mat- 

 ter, we may obtain at pleasure various products, and in pro- 

 portions very different. 



The best proportions to produce the colouring matter, are 

 100 parts of nitric acid, at 34° (S. G. 1.307?), mixed with 

 100 parts of water, and 50 parts of uric acid, at a low heat. 

 The solution obtained has a fine scarlet colour. If fresh quan- 

 tities of nitric acid be added to it, and boiled, tlie red colour 



