102 ANIMAL CHEMISTRY. 



there were formed in it long prismatic, brownish crystals, in great quantity, which even 

 in this state, could not be taken for benzoic acid. Another portion, evaporated to the 

 consistence 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 

 charcoal, and recrystallized. By this means the acid was obtained in colourless prisms, 

 an inch in length. 



Their crystals were pure hippuric acid. When heated, they melted easily; and when 

 exposed to a still stronger heat, the mass was carbonized, with a smell of oil of bitter 

 almonds, while benzoic acid sublimed. To remove all doubts, I determined the propor- 

 tion of carbon in the crystals, which I found to be 60-4 per cent. Crystallized hippuric 

 acid, according to the formula C'WNO 6 -!- HO, contains 60*67 per cent, of carbon; crys- 

 tallized benzoic acid, on the other hand, contains 69-10 per cent, of carbon. 



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 inju- 

 rious 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 contained 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 normal urine. 



The inspissated urine, after the hippuric acid had been separated by muriatic acid 

 yielded, on the addition of nitric acid, a large quantity of nitrate of urea. It had pre 

 viously 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 is certainly too hasty in recommending ben- 

 zoic 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 hip- 

 puric acid; but as his observations were made on a gouty patient, 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, because it only separated after the addition of an acid. 



THE EK1X 





