THE LACTATES, AND UREA AS IT EXISTS IN URINE. 157 
gent taste. The sulphuric acid may be separated by baryta, 
and the urea re-obtained by absolute alcohol. This salt has 
not been previously described. • 
If the lactate of urea is to be obtained by double decompo- 
sition from an oxalate of that base, this latter is to be first dis- 
solved in a little distilled water, then an aqueous solution of the 
lactate of lime is cautiously added , so that neither salt shall pre- 
dominate. The solution is filtered and evaporated at a moderate 
heat, or still better, in vacuo, when the lactate of urea will not 
fail to crystallize. If the sulphate of urea and lactate of bary- 
ta are used, analogous results will be obtained. It only re- 
mains to re-dissolve the crystals and purify them by re-crys- 
tallization. 
The lactate of urea, as it exists naturally in human urine, is 
of difficult isolation ; on the one hand, on account of the excess 
of lactic acid contained in the organic liquid, and on the other, 
on account of the great solubility of this salt, which requires 
an advanced state of concentration for its crystallization ; and, 
finally, on account of its extreme volatility, which requires 
that this concentration should be made with the greatest amount 
of care. 
To ascertain the mean amount in which this salt exists in 
urine, we evaporated a killogramme of healthy urine, made 
during night, to the consistence of a very clear syrup ; it pro- 
duced a deposit of white and confused salt, which was separat- 
ed by the filter. The liquid was shaken with carbonate of po- 
tassa, to separate any excess of acid, and evaporated again un- 
til a saline product began to appear, which, on cooling, became 
very abundant. The whole was then put in contact with a 
mixture of two parts of alcohol of 33°, and one part of ether. 
This was heated moderately, frequently shaken during three 
days, and then filtered. The ethereal liquid, on being dis- 
tilled, left behind, as a residue, 18 grammes of lactate of 
urea, crystallized in prismatic needles of a slightly yellow 
color. 
This proportion of lactate obtained, does not represent the 
whole amount of the urea ; a similar quantity of healthy urine 
