It suffices to cause the current
of water which issues from the condenser of the frigorific machine to
pass into the worm of the boiler.
We have, then, two results, two like operations, both produced by
the working of a single machine. Moreover, these two operations are
performed _in vacuo_, and we know that under these conditions they are
effected at lower temperatures. Owing to this fact, likewise, the weight
of the water that must be evaporated diminishes just so much. Now, one
kilogramme of water requires 636 heat units to cause it to pass from the
liquid to the gaseous state, while one kilogramme of alcohol requires
only 230 heat units to vaporize it. Thus every decrease of temperature
in rectification has for an immediate corollary an important economy of
fuel, which is proved by the diminution of radiation, and by the less
quantity of water to be distilled.
Between the boilers, A, in which is maintained a temperature bordering
on +50 deg. to +60 deg., and the refrigerator, H, in which is easily
obtained a temperature of -30 deg. to -40 deg., there is at our disposal
a range of temperature of nearly 100 deg., an immense difference
compared with that which can be made use of in ordinary apparatus.
Thanks to this powerful factor, which is manageable at will, we can
take directly from the apparatus alcohols marking 98 and 99 degrees by
the centigrade alcoholmeter.
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