DISTILLATION OF LACTIC ACID, 
73 
tilled ; what passes over at 42S° is saturated with carbonate 
of baryta, when the salt, which is perfectly insoluble in 
alcohol, fallsas a crystalline paste. This is dissolved in boiling 
water, from which solution the citraconate of baryta sepa- 
rates on cooling in beautiful nacreous laminae, which are 
obtained of the largest size when the solution is concentrated 
until a pellicle forms on the surface. The air-dried salt lost 
at 212°, 14-82, 14-49, 14-93 and 14-29 per cent, or 5 atoms 
of water. The salt, dried at 212°, furnished — 
Carbon, 
22-57 
22-80 
10 
22*61 
Hydrogen, 
1-81 
1-93 
4 
1-51 
Oxygen, A . 
1815 
17-40 
6 
1809 
Baryta, 
57-47 
57-S7 
2 
57-79 
Lactic Acid, — This 
is left, either in 
the an 
hydrous or 
hydrated state, in the retort, in the preceding distillation of 
citraconic acid. 
In one experiment, in which 19-5 grms. of anhydrous 
lactic acid were exposed to a temperature of 500°, and 
which was continued for eight hours, the author obtained 
12-2 percent, aldehyde, 14-9 lactide, and 1 per cent, carbon. 
Several experiments made at the same temperature fur- 
nished approximative results. On raising the temperature 
above 500°, for instance to 572° and higher, the amount of 
lactide and lactic acid is diminished and that of the aldehyde 
increased. As the disengagement of gas is far more violent, 
the gases must be much more carefully cooled, in order to 
prove directly the increase of the aldehyde. The lactide 
formed is for the greater part decomposed into aldehyde 
and carbonic oxide by this temperature, which is much 
above that of the point of sublimation. The decomposition 
of the lactic acid is therefore simply as follows : At first 
lactide is produced, and this is decomposed at a higher tem- 
perature into 2 equivs. carbonic oxide and 1 equiv. alde- 
hyde, C 4 W O 2 +2CO=C 6 W 4 . The presence of car- 
bonic acid and the composition of citraconic acid tend to 
7 
