Such results are unobtainable by the usual
methods.
We have likewise ascertained that at low temperatures the ebullition of
alcohol is as active as at near 100 deg..
For a same range of temperature between the boiler and the refrigerator,
the weight of alcohol which distills in an hour is constant. By the
operation of the valve, D, it becomes easy to allow all the liquid
condensed in the first refrigerator to pass into the second boiler;
and thus the second rectification, which is effected in a more perfect
vacuum, is supplied with exactness. The object of this valve, then, is
to allow the liquid to pass, and yet to cut off the pressure in such
a way as to have a double fall of temperature throughout the whole
apparatus; from 60 deg. to 20 deg. in the first operation, and from
0 deg. to -40 deg. in the second. We may add that the regulation of the
valve is extremely easy, because of the screw which actuates it.
To sum up the commercial advantages that our process procures, we may
say that it realizes the following _desiderata_: 1. With the cost of a
single distillation we have, at once, distillation and rectification,
or a single expense for two results. 2. With one operation at a low
temperature we obtain products which are almost impossible to get even
by an indefinite number of rectifications at a high temperature, the
temperature having an intrinsic value in the operation.
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