14 CONVERSION OP BENZOIC INTO HIPPURIC ACID. 
it shows that urea is also dissolved by this process. The 
same proceess of extraction was repeated with a fresh por- 
tion of the same mixture, and with the same results ; but 
the evaporation was not carried so far, in order to be able 
to examine the mother-liquid. We obtained a crop of crys- 
tals of pure urea, containing no hippuric acid, while the 
mother-liquid had a bitterish taste, but did not yield hippu- 
ric acid by the addition of chlorohydric acid. It was 
therefore evident that the above mixture extracted pure 
urea, while it left behind the combination of hippuric acid* 
We next employed a mixture of equal volumes of alcohol 
and ether, which dissolved a much larger quantity from the 
original syrup, but on evaporation yielded only a slight 
crop of crystals. The greater part of it remained as a 
thick syrup, yielding an abundance of crystals of hippuric 
acid by the addition of chlorohydric acid, but also a large 
amount of nitrate of urea by the subsequent addition of 
nitric acid. It was therefore evident that the compound of 
hippuric acid was also extracted by the last treatment, and 
it merely remained to find the base. A few drops of the 
syrups charred and incinerated, left no residue, proving the 
absence of all the fixed bases of the urine. The hippuric 
acid could therefore only be combined with urea or ammo- 
nia, to ascertain which chlorohydric acid was added to a 
portion of it, and after the separation of the hippuric acid, 
chloride of platinum added, which caused a very copious 
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 precipi- 
tate 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 cor- 
