A Manual of the Chemistry of the Carbon Compounds

CH8
THE CARBON COMPOUNDS. 209
CH8
HBr + AgOH « CH.OH + AgBr
Ao.OH
CO.OH
(3) Anhydrous prussic acid unites with aldehyde, forming the compound
CLH.O.CNH, a liquid boiling with partial decomposition at
183°, Alkalis decompose it again into its constituents, but hydrochloric
acid converts it into ammonium chloride and lactic acid:—
CH3
CH8
|
I + CNH + 2H2O + HC1 = CH.OH + NH4C1
COH I
CO.OH
Lactic acid exists in the gastric juice and in Turkey opium, and it
is also produced by the lactio fermentation of sugar, gum, and
starch. It occurs therefore in sour milk, sour cabbage, in the fermented
juice of beetroot, and in spent tan. It is also formed together
with other products when grape-sugar is heated with a solution of
caii8tic soda.
Lactic acid is easily obtained in quantity by the following process:
3 kilograms of cane-sugar and 15 grams of tartaric acid are dissolved
in 17 litres of boiling water, After the solution has stood for a few
days, 100 grams of putrid cheese and 1*2 kilograms of zinc-white,
which have been mixed to a creamy liquid with 4 litres of sour milk,
are added, and the mixture & exposed to a temperature of 30°—35°
for eight or ten days. The product is heated to the boiling-point,
filtered, and evaporated to crystallization. The zinc lactate thus obtained
is purified by recrystallization from boiling water, then dissolved
in -water, decomposed by hydrogen sulphide, and the filtrate
evaporated on a water-bath. The residue, consisting of impure lactio
acid, is dissolved in a small quantity of water and the solution shaken
with ether. On evaporating the ethereal solution pure aqueous lactio
acid is obtained, forming a colourless, syrupy liquid, possessing a very
sour taste,
LACTATES.
The laotates of the alkali metals are very soluble in water, and do
not crystallize.
Calcium lactate (C8H.O3)2Ca + 5H8O crystallizes from a hot aqueous
solution in warty needles. Zinc lactate (CjILO^Zn + 3H,0 is the
most characteristic salt of this acid; it crystallizes in shining foursided
prisms, and dissolves in six parts of boih'ng and fifty-eight parts
of cold water; it is insoluble in alcohoL Ferrous lactate (CHOJF
C