72 
DISTILLATION OF LACTIC ACID. 
Jildehyde. — When the distillate, either in the state of 
liquid or as a crystalline paste, is heated in a water bath to 
212°, and the new product passed into anhydrous sether 
kept cold, this subsequently yields, on passing ammonia 
through it, aldehyde ammonia. 
Lactide. — The residue from the preceding treatment, 
from which the aldehyde has been removed, forms a brown- 
ish liquid, which in most cases again solidifies to a crystal- 
line paste, which is thrown upon a filter, washed with cold 
absolute alcohol, and dried by pressure between bibulous 
paper. In order to obtain large crystals, it is redissolved 
in a little boiling absolute alcohol and set aside to cool. 
What does not crystallize on cooling is lost, from its be- 
coming converted, both by spontaneous evaporation and 
by heat, into ordinary lactic acid. The crystals appear to 
belong to the rhombic system, and exhibit great resemblance 
to those of the protosulphate of iron. Lactide cakes some- 
what together at 248°, and can be sublimed, but it proceeds 
very slowly. At a higher temperature it melts, sublimes 
more quickly, and furnishes at 500° the same products of 
decomposition as the anhydrous lactic acid. Lactide also 
behaves exactly like anhydrous lactic acid towards water, 
alkalies and alkaline earths. It is reconverted into hydrated 
acid. It is, however, more soluble in boiling water than 
the anhydrous lactic acid, and again separates for the greater 
part on cooling in small needles. It has neither smell nor 
taste, but very soon acquires, with the assimilation of water, 
a strongly acid taste. Lactide, dried in vacuo, furnished on 
analysis — 
Carbon, . . 49*87 6 50 00 
Hydrogen, . 567 4 5-56 
Oxygen, . 44-46 4 44-44 
Citraconic Jicid is produced only in small quantity. The 
alcohol with which the crystals of lactide were washed, 
contains this acid and also lactic acid ; it is filtered and dis- 
