346 Liquefaction and Solidification of Carbonic Acid. 



it was done but yesterday. The limbs are very much flattened, 

 but otherwise, their external appearance is the same as usual in 

 the species, which can easily be determined, being oak, walnut, 

 hickory, &c. The larger logs and fragments have undergone the 

 transformation in various degrees, some being of a soft and spongy 

 texture. Many are in the state of perfect coal at one end, or on one 

 side, and have undergone no change except softening at the other. 



Art. XVI. — On the Liquefactio?i and Solidification of Carbonic 

 Acid;* by J. K. Mitchell, M. D. 



In the year 1823, public attention was strongly drawn to the 

 subject of the liquefaction by pressure of the, so called, perma- 

 nent gases, by Mr., now Sir Michael Faraday.f Among the 

 aerial fluids, carbonic acid was distinguished as requiring a force 

 of 36 atmospheres at 32° F. to coerce it into the liquid state. 

 His ingenious and hazardous experiments were conducted in 

 glass tubes ; and he depended on the accumulation of newly 

 generated gas for the necessary pressure. 



Mr. Brunei,:^ in a subsequent endeavor to apply compressed 

 gases to mechanical purposes, produced a pint and a half of liquid 

 carbonic acid, which, even at high temperatures, he confined in 

 a series of small brass tubes not above the 3'^ of an inch in the 

 thickness of their walls. ' - 



This interesting subject was not again publicly agitated, until 

 the appearance in December, 1835, of a report on the liquefac- 

 tion of carbonic acid on a comparatively large scale. In the last 

 number for that year of the Atmales de Chimie et de Physique, 

 M. Thilorier described the properties of liquid carbonic acid in 

 detail. According to him, this liquid demands for its existence 

 as such at 32° P., a pressure, as stated by Sir M. Faraday, of 36 

 atmospheres. Its specific gravity is at the same temperature 

 0.830, at —4° F.— 0.900, and at 86°— 0.600. It is therefore en- 

 larged by heat 3.407 times as much as its own or any other gas, 

 when carried from 32° to 86°. From — 4° to 32°, its expansion 

 is almost exactly equal to that of the gases.<§. 



* From the Journal of the Franklin Institute. 



t Philos. Trans. Lond. t Q,uart. .louni. Vol. xli. 



§ See at page 301 of this number, a notice of Mr. Robert Addams' experiments 

 on this subject, and that of Dr. Torrey, in our miscellany. — Eds. 



