514 On the two great powers, [Ocr. 
This Lavorster himself has enforced. After some former remarks 
he continues thus* : ‘‘ Whence it appears, that without this atmos- 
pheric pressure we should not have any permanent liquid, and should 
only see bodies in that state of existence in the very instant of melt- 
ing; for the smallest addition of caloric would then instantly separ- 
ate their particles, and dissipate them through the surrounding me- 
dium.” This doctrine this great philosopher has supported by ex- 
periments on liquids placed in vacuo, which rapidly pass into vapor on 
the removal of atmospheric pressure. 
Although most of these experiments appear to confirm the above 
doctrine, yet I may state certain objections which appear to me unan- 
swerable. Though most liquids do pass into vapor under the ex- 
hausted receiver, yet there are some, such as concentrated sulphuric 
acid, which scarcely appear to do so. This acid (as is well known in 
what is named the freezing experiment) by its great attraction condens- 
es aqueous vapor formed in an exhausted receiver, and thus preserves 
a partial vacuum. It not only remains in the liquid state itself, but 
also condenses the vapor from the vacuum. 
Again, If even all liquids could be shown to vaporize at natural 
temperatures in vacuo, it would not be any proof of the doctrine, ow- 
ing to the imperfect nature of the experiment itself. Any liquid un- 
der the pressure of the air, must soon be of the same temperature with 
the air, i.e. endeavour to part with heat with the same force: but as 
soon as the atmospheric pressure is removed, a great force, tending 
to expel heat from the liquid, is removed ; the effort therefore of the 
liquid to expel heat becomes less than before, and therefore less 
than the effort of the circumjacent air. The consequence of this 
must be, a continual passage of heat from the air to the liquid, and its 
vapor, which will make the evaporation unlimited. Were it possi- 
ble to procure a receiver which should not be permeable to heat, there 
-would soon be a limit to the evaporation of a liquid, and the receiver 
would doubtless remain exhausted. It is certainly true, that under 
such circumstances, water would not remain a liquid, and a small part 
of it would pass into vapor, most of it would become ice. But ether, 
alkohol, and other liquids which would resist freezing, would proba- 
bly continue as liquids in a receiver impermeable to heat. The receiv- 
ey of any air-pump is in a similar situation to that of a common pump; 
except that on the removal of the pressure, heat is forced into the 
former and water into the latter, by the very same force ; namely, the 
* Elements of Chemistry, translated by Kerr, page 56, 
