186 Dr. Channing on the Reaction of Solid Carbonic Acid, Sse. 
11. Solid carbonic acid was compressed in contact with hy- 
drated acetate of lead, a salt readily attacked by carbonic acid, 
but no sensible heat was evolved. 
2. 'To obtain some indication of the amount of heat which 
be near the melting point of tin, though actual fusion could not 
be effected by any arrangement. A splinter of pine brought in 
contact with the foil was slightly discolored, and gave the char- 
acteristic smell of charred wood. 'The temperature may there- 
fore be safely estimated at between 350° and 400° FE’. By sub- 
stituting a slip of platina foil above and below the reagents, in 
place of the tinfoil, ether, alcohol and water dropped upon it, were 
successively vaporized. Phosphorus was instantly inflamed on 
touching the foil. A piece of fusible metal placed upon the foil 
was melted. | 
13. Hydrate of potash and solid carbonic acid were ground to- 
gether in a small mortar. Sufficient heat was produced to ex- 
plode gun-cotton, but the experiment is an undesirable one for 
repetition. 'The experiment with gun-cotton in ¢3 may be di- 
but not in contact with the gun-cotton. The alcohol is then ig- 
nited by the explosion of the latter. 
4, The reaction of solid carbonic acid with liquids and solu- 
tions, is referable, to some extent, to the same principle as its re- 
action with bases in the dry state. When immersed in water, it 
combines with this latter, and at the same time the evolution of 
gas is so rapid as to prevent the solid from touching the liquid. 
Owing to these causes the temperature of the water falls only a 
few degrees, instead of the anticipated result of immediate con- 
gelation, and the thermometer held in the gas escaping from the 
surface indicates a temperature slightly above that of the surround- 
ing air, this heat being the heat of combination, evolved at t 
point of union of the carbonic acid and the water, acting as a 
base. With a solution of potash the reaction is very much t 
same, the only observable point being the great quantity of gas 
which escapes absorption. 
_ 15, When solid carbonic acid is treated with ether or alcohol, 
it assumes a semi-fluid state, and no chemical combination prob- 
ably taking place, and the vaporization of the acid being aug- 
mented, these mixtures become of the most frigorific character, 
and are commonly used for this purpose. When however hy- 
drate of potash is added to these in a mortar, the mixture with 
ether rises to a temperature probably above 40° F., and that with 
alcohol still higher, with occasional violent ebullition. By 
