166 



DR. FARADAY ON THE LIQUEFACTION AND SOLIDIFICATION OF 



atmospheres, whilst Addams makes it only 34*67 atmospheres. At 86° Thilorier 

 finds the pressure to be 73 atmospheres; at 4° more, or 90°, Brunel makes it 120 

 atmospheres ; aud at 10° more, or 100°, Addams makes it less than Thilorier at 86°, 

 and only 62*32 atmospheres; even at 150° the pressure with him is not quite 100 

 atmospheres. 



I am inclined to think that at about 90° Cagniard de la Tour's state comes on 

 with carbonic acid. From Thilorier's data we may obtain the specific gravity of 

 the liquid and the vapour over it at the temperature of 86° Fahr., and the former is 

 little more than twice that of the latter ; hence a few degrees more of temperature 

 would bring them together, and Brunel's result seems to imply that the state was 

 then on, but in that case Addams's results could only be accounted for by supposing 

 that there was a deficiency of carbonic acid. The following are the pressures which 

 I have recently obtained : — 



Fahr. 



^— lii 



— 110 



V— 107 



— 100 

 v'— 95 



— 90 

 ^— 83 



— 80 



^— 75 



— 70 



Atmospheres. 



•14 



•17 

 •36 



•85 

 •28 



•77 

 •60 

 •93 

 •60 

 •33 



Carbonic acid is remarkable amongst bodies for the high tension of the vapour 

 which it gives off whilst in the solid or glacial state. There is no other substance 

 which at all comes near it in this respect, and it causes an inversion of what in all 

 other cases is the natural order of events. Thus, if, as is the case with water, ether, 

 mercury or any other fluid, that temperature at which carbonic acid gives off vapour 

 equal in elastic force to one atmosphere, be called its boiling-point ; or, if (to pro- 

 duce the actual effect of ebullition) the carbonic acid be plunged below the surface 

 of alcohol or ether, then we shall perceive that the freezing and boiling-points are 

 inverted, i. e. that the freezing-point is the hotter, and the boiling-point the colder of 

 the two, the latter being about 50° below the former. 



Euchlorine. — This substance was easily converted from the gaseous state into a 

 solid crystalline body, which, by a little increase of temperature, melted into an 

 orange-red fluid, and by diminution of temperature again congealed; the solid euchlo- 

 rine had the colour and general appearance of bichromate of potassa ; it was mode- 

 rately hard, brittle and translucent; and the crystals were perfectly clear. It 

 melted at the temperature of 75° below 0°, and the solid portion was heavier than 

 the liquid. 



