352 = Liquefaction and Sol dif ication of Carbonic Acid. 
at the time of the formation of the solid. In my experiments, a 
constant decrease of temperature was observed, which was accel- 
erated by a current of air, or any other means of augmenting 
“evaporation. At its formation, the carbonic snow depresses the 
thermometer to about —85°. If it be confined in wool or raw 
cotton, its cooling influence is retarded ; if it be exposed to the 
air, especially when in motion, the theraganaier descends much 
more rapidly ; and under. the receiver of an air pump, the effect 
is at its maximum. The greatest cold produced by the solid car- 
bonic acid in the air was —109°, under. an exhausted receiver 
—136°, the natural temperature being at +86°. : 
The admixture of sulphuric ether so as to produce the appear- 
ance of wet snow, increased the coldness, for the temperature 
then fell, under-exhaustion, to —146° ;* a degree of cold which 
we were not able to exceed by means of any variation of the 
experiment. That result is most easily obtained by putting 
about two fluid drachms of ether into the iron‘receiver before 
charging it. A compound liquid may be thus formed which 
yields a snow in less quantity, but of a more facile refrigeration. 
Alcohol may replace ether in either mode, but with less decided 
“effect. In the air, the alcoholic mixture fell to —106°, and re- 
mained stationary. By blowing the breath on it, it fell to —110°. 
Left to itself, it rose slowly to —106°; but on being placed un- 
der an exhausted receiver fell to 1340. 
Every attempt to wet the carbonic solid with water, Siilede: so 
that no estimate of its relative effects could be made. 
_ The experiments resulting from the great coldness of the new 
solid, were very striking. Mercury placed in a cavity in it, and 
covered up with the same substance, was : frozen in a few scconds, 
But the solidification of the mercury was almost instantly pro- 
duced by pouring it into a paste made by the addition of a little 
ether. Frozen mercury is like lead, soft, and easily cut. It is 
ductile, malleable, and insonorous. Just. as it is-about to melt, - 
it becomes brittle or “short,” and breaks under the point of a 
‘knife. These facts may account ‘for the discrepancies of authors 
on this subject: Frozen mercury sinks readily in liquid mer- 
cury. 
-* "As —6432= 175, the cold is nearly as far below the eens —32 
=180 is above it 
