256 PROCEEDINGS OP THE AMERICAN ACADEMY 



XII. 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



ON THE ETHERS OF URIC ACID. 



SECOND PAPER. 

 DIMETHYLURIC ACID. 

 By H. B. Hill and C. F. Mabert. 



Presented April 14, 1880. 



Dimethtltjrtc acid is formed when di plumbic urate is heated with 

 methyl iodide according to the general method which one of us has 

 already described * for making the monomethyl compound. The prep- 

 aration of considerable quantities of pure substance by this method 

 is,' however, a matter of some difficulty, and we have found that a 

 close attention to details is necessary to insure success. 



The diplumbic urate which we used at first was made according to 

 the directions of Allan and Bensch,f by precipitating a boiling solu- 

 tion of plumbic nitrate with dipotassic urate purified by alcohol. 

 Although we heated this lead salt with an excess of methyl iodide at 

 various temperatures (100° to 170°) for different lengths of time (five 

 to ninety hours), we could not succeed in obtaining from it a product 

 which did not contain quite a large percentage of the monomethyl ether. 

 We therefore attempted to effect the separation of the monomethyl 

 and dimethyl compounds by fractional crystallization, or by methods 

 based upon differences in the behavior of their salts ; but we were 

 unable to find a method which was at all satisfactory, and, after many 

 experiments, convinced ourselves that it was necessary to obtain from 

 the first a product essentially free from the monomethyl compound. 



After a long series of experiments which need not be described in 

 detail, we found that such a product could be obtained from a lead 



* These Proceedings, Vol. XII. p. 27. 

 t Ann. Chem. u. Pliarm., lxv. 191. 



