_ Liquefaction and Soli dific ati ‘s Carbonic Acid. 351 
to which 24 fluid ounces of awitde rare to be added. After ma- 
king these into a thin paste: by sti irring; 9 fluid ounces of com- 
mon sulphuric acid are to be poured into ‘the copper cup, N, and 
that is to be let down by a ‘crook. of wire into the generator. 
' After the screw, E, has been firmly applied, and the stop-cock, 
J, closed, the contents of the generator are to be brought into ad- 
mixture by moving it round to a horizontal-position on the swivel 
D, which is supported ‘by the wooden frame, B, B. There i isa 
check bar atC.. This motion isto be repeated several times. In 
about ten minutes the whole of the carbonic acid is pcre 
and exists in.A, chiefly in a liquid state. 
The next step in the process is to attach, by means of the stir- 
rup and screw, K, K, the receiver, F', previously cooled by ice. 
The keys, Iand J ay then be panied slowly, and instantly the 
liquid carbonic acid is perceptible in the gauge, L. At the end 
of ten minutes, the communication with the generator may be 
cut off—when about -eight fluid o liquid acid at 32° F. 
will be found in the receiver. ; 
By letting this liquid into the box, 0, through the - pipe, G 
large part of it is instantly expanded: into gas, whieh « escapes 
through the tube, P.. The coldness consequent on the enormous 
expansion, freezes another part of the liquid, which falls to the 
bottom of O. About one drachm of solid matter is thus cases 
for each ounce of liquid. 
The porosity and volatile character of the solid Be its ‘spe- 
cific gravity of difficult ascertainment. When recently formed, it 
is about the weight of carbonate of magnesia, and when strongly 
compressed by the fingers, its density is nearly doubled. Solid 
carbonic acid is of a perfect whiteness, and of a soft and spongy 
textufe, very like slightly moistened and aggregated snow. It 
evaporates rapidly, becoming thereby colder and colder, but the 
coldness produced seems to steadily lessen the evaporation, ‘so 
that the mass may be kept for-some time. A quantity weighing 
346 grains lost from 3 to 4 grains per minute at first, but did not 
entirely disappear for three hours and a half. The nati tempe- 
rature was from 76° to 79°. ‘The solid is most easily kept when 
compressed and rolled up in cotton or wool. Its temperature 
when newly formed is not exactly ascertainable, because it is im- 
mediately lowered by evaporation. Thilorier seems to have en- 
pe 
“ nee 
tertained the opinion, that the greatest degree of cold was created 
