10 CONVERSION OF BENZOIC INTO HIPPURIC ACID. 
less. The crystals thus obtained behaved in all respects 
like pure hippnric acid. They fused easily, and by a 
stronger heat they charred with a smell of oil of bitter al- 
monds and sublimation of benzoic acid. He also deter- 
mined the quantity of carbon, which he found to agree 
with that of hippuric acid, namely, 60.7 per cent, while 
benzoic acid contains 69.1 per cent, of carbon. 
Keller furthermore ascertained that the urine from which 
hippuric acid had been separated, deposited a large amount 
of nitrate of urea, on the addition of nitric acid. It had 
also previously deposited uric acid. It therefore contained 
these two usual ingredients of urine. He also inferred, 
that since the urine could be inspissated without depositing 
hippuric acid before the addition of chlorohydric acid, it 
was evident that the hippuric acid existed in combination 
with a base. 
As hippuric acid may be said, to a certain extent, to re- 
place uric acid in the herbivorous mammalia, this probably 
led Ure to the supposition that the uric acid was employed 
in the conversion of the benzoic acid ; but Keller's experi- 
ment showed that the urine deposited uric acid, and that 
therefore this latter assertion could not be correct. 
We have repeated Keller's experiments, and with the 
same results. We have in general found that after the use 
of benzoic acid the urine makes a copious deposite of uric 
acid, both in the red or dark-colored variety and in that 
of a clay-colored or muddy appearance. 
In one experiment the urine was examined in the morn- 
ing when no benzoic acid had been taken. It deposited no 
sediment on cooling, and when tested for uric acid by the 
addition of nitric acid, the latter effected after twenty-four 
hours a deposite of only a few isolated colorless crystals 
scattered over the inside of the vessel. The same day two 
grammes of benzoic acid were taken immediately after 
dinner. Twenty minutes afterwards the urine was voided, 
evaporated to one-fourth its volume, and chlorohydric acid 
