402 Miscellanies. 



Communicated by Prof. J. Griscom. 



4. Properties of Liquid Carbonic Acid; by M. Thilorier. — 

 Within the walls of Faraday's tube is a new chemical world, the 

 phenomena of which are totally unexpected : to mention at this 

 time only liquefied carbonic acidj whose properties, in common with 

 permanent liquids — dilatation, vaporization, &ic. — are exalted, am- 

 plified, and developed upon a scale truly gigantic. 



Dilataiion. — This liquefied gas presents the strange and paradox- 

 ical fact of a liquid more dilated than the gases themselves ; from 

 0° to -1-30° Cent, its volume is increased from 20 to 29; that is to 

 say, at +30 Cent, the increase of volume is nearly equal to the 

 half of its volume at 0° ; in a word, its dilatation is four times 

 greater than that of air, which from 0° to +30° Cent, would be 

 dilated only -^W, whilst the dilatation of liquid carbonic acid, redu- 

 ced to the same scale, is ii|. 



Vaporization. — If we raise the temperature of a tube containing 

 a thin stratum of liquid carbonic acid, it enters into ebullition, and 

 the empty space above the liquid is saturated with a quantity of 

 vapor which increases with the temperature. At +30° Cent, the 

 quantity of liquid at 0° necessary to saturate the empty space, is 

 represented by a stratum of liquid equal to a third of the space in 

 which the evaporation was effected. At 0° the stratum of liquid of 

 saturation is only j\ of the space saturated. 



Pressure. — From 0° Cent, to +30° the pressure of the vapor 

 furnished by the liquefied gas rises from 36 atmospheres to 73 ; which 

 gives an increase of one atmosphere for each centigrade degree. It 

 is necessary to observe, that the weight or density of the vapor in- 

 creases in a much greater proportion than the pressure, and that the 

 law of Mariotte does not apply within the limits of liquefaction ; if 

 we took the density of the vapor for the basis of pressure, the pres- 

 sure at +30 Cent, would be equal to 130 atmospheres, while the' 

 manometer indicates really but 73. 



Thermoscopic effects. — If we subject to the action of heat a tube 

 of glass containing a stratum of liquid and another of gas, two con- 

 trary effects will appear. 



1. The liquid will increase by dilatation. 



2. The liquid will diminish by vaporization. 



The thermoscopic effects will be very different according as the 

 liquid stratum is greater or less than the gaseous stratum : hence the 



