THE LACTATES, AND UREA AS IT EXISTS IN URINE. 159 
Which leads to the following formula 
C*H 3 N 4 2 +C 6 H 4 4 + 0H 
The natural lactate of urea, obtained from urine, presents 
exactly similar qualities with the same salt artificially pre- 
pared. 
III. We have succeeded in obtaining many other salts of 
urea by the mode of double decomposition, which has answer- 
ed so well in the case of the lactate of this base. These salts, 
which have not been previously described, crystallize with 
great facility, and possess well characterized chemical and 
physical properties ; such are the sulphate, phosphate, hydro- 
chlorate, acetate, tartrate, and quinate of urea, with several 
others. They are, for the most part, to be obtained by treat- 
ing the oxalate of urea, by means of different salts of lime and 
alcohol. Many of them are volatile at a moderate, and de- 
composable at a higher temperature ; all are soluble in water 
and alcohol. When treated with lime, baryta, or oxide of 
silver, and the mixture agitated in alcohol, this menstruum se- 
parates crystal! izable urea, and forms a salt with the base, 
lime, baryta, or silver. The salts of urea, exposed to the ac- 
tion of nitric acid in excess, furnish a supernitrate of urea. 
These different properties suffice to distinguish them from 
ammoniacal compounds, from which they also differ by other 
characters. 
We will here remark upon the ordinary process for obtain- 
ing urea. According to this, after separating foreign salts and 
again evaporating, the liquid is allowed to become cold, and 
nitric acid then added . If the evaporation is pushed to a conve- 
nient extent, the nitrate of urea becomes a mass of small pearly 
crystals, of a gray or rose color. These crystals are drained, 
and the mother waters, separated and evaporated, furnish a 
new crop ; but all these crystals are purified with difficulty. 
We have remarked that if, in place of adding the nitric acid to 
cold concentrated urine, it be poured into hot weak urine, a 
slight reaction takes place, from which results, not a mass of 
