184 Dr. Channing on the Reaction of Solid Carbonic Acid 
Art. XXIL—On the Reaction of = Carbonic Acid with Al- 
kaline and other Bases ; by Wm. F. Cuannine, M.D. 
1. Te production of heat by the reaction of solid carbonic 
acid with a caustic alkali, was noticed by me in this Journal for 
January, 1844. A more precise series of observations on the 
same reaction, extended to a greater number of bases, will be 
found to afford some additional facts in the history of the acid, 
and to illustrate a most striking instance of the evolution of heat 
by chemical union. ‘The details of manipulation will be preserv- 
ed in the following experiments, chiefly to indicate the best mode 
of exhibiting the ‘phenomena described. 
olid carbonic acid was placed in contact successively with 
different bases, presented to it for the most part in the dry state. 
The intensity ‘of the reaction and the amount of heat produced 
- generally estimated by the effects of ignition and fusion ob- 
ined. The heat being local, and one of the substances pre- 
be being in a state of intense refrigeration, it was found that no 
accurate measurement could be made by oe a thermometer 
either in contact or subjected to radiatio 
3. A small fragment of solid ech acid, was comminuted 
as much as possible, and placed on cotton wool. A little pure 
peieniced hydrate of potash was poured upon it. A piece of gun- 
otton was laid over these, the whole covered with cotton wool, 
and compressed by a spatula. In a few seconds the gun-cotton 
exploded. Gun-cotton compressed with either carbonic acid or 
hydrate of potash separately, showed no disposition to ignite. 
A. Pure hydrate of soda was substituted for hydrate of potash 
with a similar result, acting apparently with equal intensity. The 
re hydrates o soda and potash, evaporated in silver vessels, 
contain frequently some additional water to the one atom belong- 
ing to the hydrate, which interferes with the above reaction. 
Thus if the cylinders of common hydrate of potash, which is 
evaporated at a higher heat in iron vessels, are employed, the “4 
action is more intense and the result more immediate. ‘That th 
is not occasioned by the presence of carbonate of potash, coud 
as an impurity in the hydrate, is shown by subjecting preee4 
bonate of potash itself to reaction with the carbonic acid. In 
this case no sensible heat is evolved. ‘The energetic reaction of 
solid carbonic acid with the alkalies, seems to a with the 
formation of protocarbonate. Pure potassa was also mixed with 
quicklime, and rose treated with the carbonic eatin but without 
wg increase 0 
The alkaline he were heated to redness in a platina 4 
aie before each alae rm and employed as soon as coo 
; lime exposed to solid carbonic acid, gave no indiea- 
