BENZOIC INTO HIPPURIC ACID. 189 
urea, and they also described the methods by which they had extracted the lactate of urea 
from human urine and the hippurate of urea from the urine of the horse. The former 
was repeated by Lecanu, who could obtain no lactate of urea. Cap and Henry replied, 
and gave a new method of obtaining it in crystals by shaking the inspissated urine with 
a mixture of one volume of alcohol and two volumes of ether, and evaporating the solution 
by heat over sulphuric acid in a closed vessel. Very recently Pelouze has shown, that 
neither lactate nor hippurate of urea can be obtained by double decomposition, or in any 
other way, and that they therefore do not exist, and that Cap and Henry had nothing 
but urea, which had imbibed the acids. 
If hippurate of urea therefore existed, it would not be improbable that this acid might 
occur combined with urea in the urine, and in our experiments particular attention was paid 
to this point. ‘The urine was evaporated, filtered, and further evaporated in a water-bath to 
a thick syrup, and then left at rest for several weeks, in the hope that the combination of 
hippuric acid would crystallize. A quantity of crystals appeared, which, being well drained 
from the mother-liquid, were found to contain no hippuric acid. They consisted chiefly of 
chlorides of ammonium and sodium, with the phosphates of the same bases. The mother- 
liquid, on the contrary, formed nearly a solid mass when tested for hippuric acid by the ad- 
dition of chlorohydric acid. By adding more water, and straining the mother-liquid from 
the crystals, subsequent addition of nitric acid caused an abundant precipitate of nitrate of 
urea. ‘I'he main mass of the syrup was now shaken for several days in a closed bottle with 
a mixture of one.volume of alcohol and two volumes of ether, which were decanted and 
evaporated by heat over sulphuric acid. While concentrating, it yielded prismatic crystals, 
and finally the whole was converted into a mass of crystals with but little mother-syrup. 
The crystals were carefully dried between blotting paper. They were, therefore, obtained 
according to Cap and Henry’s directions for extracting the lactate of urea; but they 
proved to be pure urea, so that unless the lactic acid has been employed in the formation 
of hippuric acid, lactate of urea is not obtained in this way, and at all events it shows that 
urea is also dissolved by this process. ‘The same process of extraction was repeated with 
a fresh portion 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 erystals of pure urea, containing no hippuric acid, while the mother-liquid had a 
bitterish taste but did not yield hippuric 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 alcohot 
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 al] the fixed 
bases of the urine. The hippuric acid could therefore only be combined with urea or 
ammonia, 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 
VOL. IX.—-51 
