CONVERSION OP BENZOIC INTO HIPPURIC ACID. 13 
shaking the inspissated urine with a mixture of one 
volume of alcohol and two volumes of ether, and evapo- 
rating 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 quan- 
tity 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 so- 
dium, 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 addition 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. The 
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 eva- 
porated by heat over sulphuric acid. While concentrating, 
it yielded prismatic crystals, and finally the whole was con- 
verted 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, lac- 
tate of urea is not obtained in this way, and at all events 
2 
