294 
Evaporation in Vacuo . 
be dried more readily than by means of fire, and will not 
experience those changes which the action of heat never 
fails to produce. Moreover, this method of evaporating 
requires hardly any expense, for the sulphuric acid or the 
potash made use of, need only be exposed to fire to drive 
off the moisture they have imbibed, without any loss of 
the articles themselves. 
This new method of evaporating in vacuo, may also be 
applied with success to the distillation of spirituous liquors, 
as I have satisfied myself by some trials made with this 
view. Having by means above described driven out all 
the air contained in the head of an Alembic to the beek of 
which I had kited a matrass, I placed the head upon a plate 
whereon there were also placed a capsule full of sulphuric 
acid, and another of weak spirit of wine. I carefully luted 
the junctures, the spirit of wine was raised in vapour, the 
watery part or phlegm was absorbed by the acid of vitriol, 
and the rectified spirit was distilled into the matrass by the 
sole heat of the atmosphere, which was at that time from 
18 to 20. (72 to 77 of Fahrenheit if Reaumur’s scale be 
meant, and 64 to 68 of Fahrenheit if Celsius’s or the Cen- 
tyrade thermometer be meant. I am in doubt which is 
referred to here.) 
This method of distilling by evaporation without fire,, 
seems to me too much neglected at a time when the 
scarcity of fuel renders it desirable to diminish the con- 
sumption as much as possible. (Mr. Watt while making 
experiments on steam during the invention of the im- 
provements made on the steam engine by himself, made 
also many experiments to distill in vacuo, but without suc- 
cess in a large way. T. C.) 
