This addition is accomplished in about five to ten hours.
The stirring is continued for three to four hours longer,
while the flask still remains immersed in the original
freezing mixture to which no further amount of ice is added.
The mixture is then allowed to stand at room temperature for eighteen
to twenty-four hours.

A 5-l. round-bottom flask is fitted with a rubber stopper or a cork
stopper coated with pitch, carrying two glass tubes, one of which
(for the entrance of steam) reaches to the bottom of the flask,
while the other extends into the open end of a condenser set for
downward distillation. The stopper should be wired into the flask.
The glass delivery tube into the condenser should not be less than a
12-mm. bore, and the condenser should consist of two 120-cm. water-cooled
condensers attached end to end. To the end of the condensing system,
an adapter is attached, the small end of which is at least 8 mm.
in bore and is fitted tightly into a stopper in a 2-l. suction flask.
To the side-arm of the suction flask is attached a tube leading to an
exhaust fan, in order to carry away the gases which are evolved during
the subsequent distillation. In the 5-l. flask are placed about 2 l.
of the sulfuric acid-acetone reaction mixture, and the flask
is then heated with a free flame and shaken occasionally.
A reaction starts at the end of about fifteen or twenty minutes,
as shown by the evolution of gas (chiefly sulfur dioxide), and is
allowed to run for about three minutes. At the end of this time,
a current of steam is passed in and continued for about three minutes.
During this period a large proportion of the mesitylene distils
and should be kept separate from the subsequent distillate.
The steam distillation is continued at such a rate that about 800 cc.
distils in twenty-five to thirty minutes and is collected as a