Into the alkaline solution, 520 g. of pure acetophenone is poured,
the bottle is rapidly surrounded with cracked ice, and the stirrer started;
460 g. of benzaldehyde (U. S. P.) are then added at once.
The temperature of the mixture should not be below 15'0 and it
should not be allowed to rise above 30'0 during the reaction.
If it tends to do so, the stirring is not sufficiently vigorous.

It is advantageous, though not essential, to inoculate the mixture
with a little powdered benzalacetophenone after stirring for half
an hour. After two to three hours, the mixture becomes so thick
that the stirring is no longer effective. The stirrer is then
removed and the mixture left to itself in an ice-box for about
ten hours. The mixture now is a thick paste composed of small
shot-like grains suspended in an almost colorless liquid.
It is cooled in a freezing mixture and then either centrifuged
or filtered on a large Buchner funnel, washed with water until
the washings are neutral to litmus, and finally washed with 200 cc.
of alcohol, which has previously been cooled to 0'0. After
thorough drying in the air, the crude product weighs about 880 g.
(yield 97 per cent of the theoretical amount) and melts at 50-54'0.
It is sufficiently pure for most purposes but tenaciously holds
traces of water. It is most readily purified by recrystallization
from four to four and a half times its weight of 95 per cent alcohol.
Eight hundred and eighty grams of crude product give 770 g.
(85 per cent of the theoretical amount) of light-yellow material
(m. p. 55-57'0) and 40-50 g. that require recrystallization.

2. Notes

The acetophenone should be as pure as possible (m. p.