ONE kilo of 90 per cent glycerol (sp. gr. 1.243) and 20 g.
of acetic acid are placed in a weighed 2-l. flask which is immersed
in an oil bath heated to 100-110'0. The flask is fitted with a
two-hole stopper, which carries a long tube reaching to the bottom
of the flask and a short exit tube. The former is connected
to a hydrogen chloride generator, the latter to a catch-bottle
and some system for absorbing any excess of hydrogen chloride.
A stream of dry hydrogen chloride is passed into the mixture.
The absorption of gas is very rapid at the start, but gradually
falls off towards the end of the reaction; the stream of hydrogen
chloride should be regulated accordingly. The flask is removed
from time to time and weighed; when the absorption of gas
practically ceases, the increase in weight will be about 875 g.
(25 per cent more than the theoretical amount).
The product is now cooled, placed in a 4-l. beaker, and treated
with solid sodium carbonate until just alkaline to litmus.
Water is added from time to time, to facilitate the reaction
with the sodium carbonate and to prevent the separation of salt;
about 500 cc. are required. The mixture is transferred
to a separatory funnel and the aqueous layer separated.
The crude dichlorohydrin, which weighs 1250 g., is distilled in vacuo.
The first fraction boiling below 68'0/14 mm. weighs 225 g., and consists
of water and some dichlorohydrin; the dichlorohydrin is collected
between 68-75'0/14 mm., and weighs about 775 g. The water is separated
from the first fraction, which is then redistilled and yields 100 g.
of dichlorohydrin. A still further amount of material (40-45 g.)
may be obtained by extracting with benzene, the aqueous layer obtained
in the neutralization process. This is, however, hardly profitable.
The neutralization and distillation will require about four hours.
The 875 g. of dichlorohydrin thus obtained boils over a
7'0 range; this is 70 per cent of the theoretical amount.
Redistillation yields 700-720 g. boiling 70-73'0/14 mm.
(57 per cent of the theoretical amount).