CARBONIC ACID. 305 



been followed by Thilorier in an apparatus by which the liquid 

 acid is procured in large quantity, which is constructed with 

 some improvements by Mr. Addams of Kensington. It con- 

 sists of two similar cylindrical vessels of strong sheet iron, 

 calculated to resist a bursting pressure of 60 atmospheres, in 

 one of which several pounds of bicarbonate of soda are decom- 

 posed at once by an equivalent quantity of sulphuric acid. The 

 gas confined within this generating vessel is afterwards allowed 

 to communicate with the second cylinder or condenser, by 

 means of a copper tube and stopcock of nice construction ; and 

 the charge is repeated several times in succession, till two or 

 three pints of the liquid acid are collected in the receiver. 

 When this liquid is allowed to escape from the receiver by a 

 small jet, a portion of it is frozen by its own evaporation, and 

 forms a white soft mass, like snow, which may be handled and 

 does not evaporate very rapidly, owing to its low conducting 

 power, although its temperature cannot be more than 148. 

 With a little ether the solid acid forms a semifluid mass, by 

 means of which mercury can be frozen in considerable quantity. 

 The sp. gr. of the liquid is 0.83 at 32 ; it dilates remarkably 

 from heat, its expansion being four times greater than that of 

 air, 20 volumes of the liquid at 32 becoming 29 at 86, and its 

 density varying from 0.9 to 0.6 as its temperature rises from, 

 4 to 86. It mixes in all proportions with ether, alcohol, naph- 

 tha, oil of turpentine and bisulphuret of carbon, but is insoluble 

 in water and fat oils. Its compound with alcohol may be fro- 

 zen, and melts at 135, which is the lowest point fixed with 

 accuracy in the descending scale of temperature.* Mr. Addams 

 has made careful experiments upon the elasticity of the vapour 

 of this liquid, at different temperatures, of which the following 

 are the results : 



ELASTIC FORCE OF LIQUID CARBONIC ACID. 



Temperature. Pounds per square Atmospheres of 



inch. 15 pounds each. 



... 280 ... 18.1 



10 ... 300 ... 20 

 30 ... 398 ... 26.5 

 32 ... 413 ... 27.6 

 50 ... 520 . . . 34.7 

 100 . . .935 . . . 62.3 

 150 . . .3496 . . . 99.7 

 * Thilorier, An. de Ch. et de Ph. t. 60, p. 427. 



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