ANALYTICAL EVIDENCE. 327 



sistence of syrup, formed, when mixed with muriatic acid, 

 a magma of crystalline scales. The crystalline mass was 

 pressed, dissolved in hot water, treated with animal char- 

 coal, and recrystallized. By this means the acid was 

 obtained in colourless prisms, an inch in length. 



These crystals were pure hippuric acid. When heated, 

 they melted easily ; and when exposed to a still stronger 

 heat, the mass was carbonised, with a smell of oil of bitter 

 almonds, while benzoic acid sublimed. To remove all 

 doubts, I determined the proportion of carbon in the 

 crystals, which I found to be 6O4 per cent. Crystallized 

 hippuric acid, according to the formula Ci 8 H 8 NO 5 + HO, 

 contains 60'67 per cent, of carbon; crystallized benzoic 

 acid, on the other hand, contains 69'10 per cent, of car- 

 bon. 



As long as I continued to take benzoic acid, I was able 

 easily to obtain hippuric acid in large quantity from the 

 urine ; and since the benzoic acid seems so devoid of any 

 injurious effect on the health, it would be easy in this 

 way to supply one's self with large quantities of hippuric 

 acid. It would only be necessary to engage a person to 

 continue for some weeks this new species of manufacture. 



It was of importance to examine the urine which con- 

 tained hippuric acid, in reference to the two normal chief 

 constituents, urea and uric acid. Both were contained in 

 it, and apparently in the same proportion as in the nor- 

 mal urine. 



The inspissated urine, after the hippuric acid had been 

 separated by muriatic acid, yielded, on the addition of 

 nitric acic, 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 colour characteristic of uric acid. This 

 observation is opposed to the statement of Ure ; and he 



