CONVERSION OP BENZOIC INTO HIPPURIC ACID. 15 
responding copious precipitate of chloroplatinate of ammo- 
nium; but on the addition of nitric acid it yielded no 
nitrate of urea nor any trace of this substance by evapora- 
tion, 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 solu- 
tion, 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 af- 
fected 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. 
