SELECTED ARTICLES. 
31 
the exhaustion is sustained, the other flask be refrigerated by 
ice and salt, the water will be frozen * 
The intelligent chemist will perceive that this apparatus 
may be applied to the purpose of desiccation by placing the 
article to be dried in one receptacle, and quick lime, chloride 
of calcium, or concentrated sulphuric acid, in the other. The 
orifice of the receptacles may be made larger without incon- 
venience. Two large cylinders, for instance, may be used. 
I propose, as soon as I have leisure, to apply the principle 
illustrated by this apparatus, to the distillation or desiccation 
of many substances which are liable to injury when exposed 
to heat, or air. I conceive that there is, by means of analogous 
apparatus, a fruitful field for improvement in the arts. I am 
of opinion that it may be employed in the preservation of 
meat, milk, fruit, vegetables, and the making of cheese; also 
in pickling and preserving. 
In these processes it would remove the necessity of resort- 
ing to a high temperature to expel water, by which means the 
flavour of the fruit is injured. 
* For the information of readers who may not be chemists, I subjoin 
the following explanation of the cause of the congelation of the water. 
So long as no condensation is effected, of the thin aqueous vapour, 
which, when water is present, must occupy the cavity of the instrument, 
that vapour prevents, by its pressure, or tension, the production of more 
vapour : but when, by means of cold, the vapour is condensed in one bulb, 
its evolution in the other, containing the water, being unimpeded, pro- 
ceeds rapidly. Meanwhile, the water becomes colder, and finally freezes, 
from losing the caloric which the vaporization requires. 
According to WoUaston, one grain of water, converted into vapour, 
holds as much caloric as would, by its abstraction, reduce thirty-one grains 
from 60® F. to the freezing point; and the caloric requisite to vapourize 
four grains more, if abstracted from the residual twenty-seven grains, 
would convert them into ice. 
