CONDENSATION OF GASES. Ill 



mercury will he rendered solid. A degree of cold, how- 

 ever, far exceeding it, has lately been obtained by the 

 use of solid carbonic acid and ether.* Solid carbonic 

 acid is itself procured from the gas liquefied by pressure ; 

 which liquid, when allowed to escape into the air, 

 evaporates so rapidly that a large quantity of it is con- 

 gealed by being robbed of its combined heat by the 

 vaporizing portion. When this solid acid is united with 

 ether, a bath is formed in which the carbonic acid will 

 remain solid for twenty or thirty minutes. By a mix- 

 ture of this kind, placed under the receiver of an air- 

 pump, a good exhaustion being sustained, a degree of 

 cold 166 below zero is secured. By this intense cold, 

 many of the bodies which have hitherto been known to 

 us only in the gaseous state have been condensed into 

 liquids and solids. Olefiant gas, a compound of hydro- 

 gen and carbon, w r as brought into a liquid form. Hy- 

 driodic and hydro bromic acids could be condensed into 

 either a liquid or a solid form. Phosphuretted hydro- 

 gen, a gas which inflames spontaneously when brought 

 into contact with the air or with oxygen, became a 

 transparent liquid at this great reduction of temperature. 

 Sulphurous acid may be condensed, by pressure and a 

 reduction of temperature, into a liquid which boils at 14 

 Fahrenheit, but by the carbonic acid bath it is converted 

 into a solid body, transparent and without colour. Sul- 

 phuretted hydrogen gas solidifies at 122 below zero, and 

 forms a white substance resembling a mass of crystals 

 of sea- salt. 



A combination of the two gases, chlorine and oxygen, 

 becomes solid at 75, and the protoxide of nitrogen at 

 150. Cyanogen, a compound of carbon and .nitro- 

 gen the base of prussic acid is solidified at 30 below 



* Proprietes de I Acide Carbonique liquids, par M. Thilorier; 

 Annales de Chimie, vol. Ix. p. 427. Solidification de I Acide Car- 

 bonique: Ibid. p. 432. 



