160 THE LACTATES, AND UREA AS IT EXISTS IN URINE. 
colored plates, but white plates of the supernitrate, completely 
pure, and not in less quantity than is furnished, with more trou- 
ble, by the former modes. We would hence conclude that the 
precaution of cooling the mixture has no advantage ; on the con- 
trary, by acting with heat, a nitrate is obtained, from which pure 
urea is separated with greater facility. To ascertain whether 
this mode effected any sensible alteration in the organic base, 
we converted two grammes of dry urea into supernitrate, with 
the assistance of moderate heat. After evaporating almost to 
dryness, the salt was treated with carbonate of potassa, and 
then by cold alcohol of 38°, which extracted a weight of urea 
equal to 1.89 ; a slight loss well compensated by the extreme 
simplicity of the new mode of extracting this base. 
The researches of which we have presented the results, are 
butthe first part of the labor to which we have applied ourselves, 
and which has for its object the therapeutic action of lactic 
acid, the lactates and salts of urea. For the present, we have 
arrived at the following conclusions : 
1. Urea does not exist in a free state in urine. 
2. In man, this base is combined principally with lactic 
acid ; in the ruminants, with hippuric acid ; in serpents and 
birds, with uric acid, or, at least, a peculiar acid which, ac- 
cording to M. Liebig, is its radical. 
3. The natural lactate of urea, extracted from human urine, 
is identical with that prepared artificially. 
4. The salts of urea are readily obtained by double decom- 
position. 
5. Finally, the properties of lactic acid would lead us to the 
hope of finding, in the lactates, new and powerful therapeutic 
remedies. 
The continuation of these researches will have for its object 
the means of obtaining, readily and abundantly, the lactic acid, 
and its combinations for physiological and medical experi- 
ment. 
Journ. de Pharm. 
