THE LACTATES, AND UREA AS IT EXISTS IN URINE, 155 
The lactic acid is prepared by means of these lactates of 
lime and baryta. The most simple process is that described 
by M. Pelouze, in the Annales de Chimie et de Physique. 
When in the state of liquid it is to be concentrated in vacuo. 
On the large scale, we may apply to this operation an appa- 
ratus proposed by one of us for the concentration of liquids 
free from atmospheric contact. This apparatus consists of a 
retort adapted to a refrigerant of large capacity ; this refrige- 
rant is provided at its base with a stop-cock, and at its side 
with an exhausting pump, both exactly fitted. The lower 
stop-cock being closed, and the apparatus exhausted, the li- 
quid is poured into'the retort by means of a funnel with a stop- 
cock, and exposed on a salt water bath to the temperature of 
50° c, or more, and thus distilled in vacuo, taking care to con- 
dense the volatile portions by means of a current of cold wa- 
ter. This apparatus, which is similar, in many respects to that 
of M. Roth, applied to the sugar refinery, offers the double 
advantage of distilling at a low temperature, and of avoiding 
the contact of air, always so prompt to alter organic com- 
pounds. 
To the already known properties of lactic acid, we may add 
the following : when treated with peroxide of lead or deutox- 
ide of barium, it is to a great extent changed into oxalic acid ; 
by the chlorites and the chlorous acid, the decomposition is 
rapid ; it forms, almost immediately, oxalates, of which the 
existence is very short, as is indicated by the effervescence 
and disengagement of carbonic acid, which almost instanta- 
neously takes place.- 
Lactic acid, even dilute, promptly dissolves moist phos- 
phate of lime ; it readily dissolves that which forms nearly 
the whole of certain animal concretions; such, for example, 
as the tartar of the teeth, which is nothing else than the phos- 
phate of lime, mixed with a little organic matter. When 
placed in contact with even large fragments of this phosphate, 
they loosen and divide spontaneously, and soon totally disap- 
pear. Finally, the oxalate of lime is soluble, to a certain ex- 
