352 Liquefaction and Solidification of Carbonic Add. 



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 thermometer descends much 

 more rapidly ; and under the receiver of an air pump, the eflect 

 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 

 eflect. 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 — 134°. 



Every attempt to wet the carbonic solid with water, failed, 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 seconds. 

 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 —146+32= 178, the cold is nearly as far below the ice-point as 212 —32 

 =180 is above it. 



