190 CONVERSION OF BENZOIC INTO HIPPURIC ACID. 
precipitate of chloroplatinate of ammonium. The addition of nitrate of silver and nitric 
acid to the liquid proved it to contain a certain amount of chlorine as chloride of ammo- 
nium, but much less than would be able to yield a precipitate so copious as the above. 
We, therefore, continued the extraction by fresh portions of equal volumes of alcohol and 
ether, and thus succeeded in obtaining a solution 'that yielded by evaporation a viscid 
mass, which, by addition of chlorohydric acid, gave an abundance of hippuric acid, and 
by subsequent addition of chloride of platinum a corresponding copious precipitate of 
chloroplatinate of ammonium; but on the addition of nitric acid it yielded no nitrate of 
urea nor any trace of this substance by evaporation, but only copious crystals of chloride 
of ammonium. It was thus made evident that urea is not combined with the hippuric 
acid, but that the base which retains it in solution and with which it is combined is 
ammonia. It also confirms the assertion of Pelouze that hippurate of urea does not exist. 
The results of the foregoing experiments may be summed up thus. 
1. The formation of uric acid in healthy urine is not affected either in regard to its 
quantity nor to its external properties in general by the introduction and transformation 
of benzoic acid into hippuric acid in the system. 
2. The time required for the benzoic acid to pass through the system, and reappear as 
hippuric in the urine, is from twenty to forty minutes after its introduction with food into 
the stomach. Its occurrence continues for four or eight hours, but then ceases. 
3. The quantity of hippuric acid obtained from the urine is greater than that of the 
benzoic acid taken. In round numbers it may be stated to be one-third more. 
4. Urea is not in combination with the hippuric acid in the urine. 
5. The base with which the hippuric acid is combined, and which keeps it in solution, 
is ammonia. 
