Bibliography. 377 
Sulphuretted hydrogen, was solidified at 122° below 0° Fahr., and is 
then a white crystalline, translucent substance, not remaining clear, and 
transparent, in the solid state, like water, carbonic acid, and nitrous 
oxide, but forming a mass of confused crystals like common salt, or 
nitrate of ammonia, solidified from the melted state. It fuses at tem- 
peratures above — 122° and the solid part sinks freely in the fluid, in- 
dicating that it is considerably heated. ‘The tension of its vapor is at 
—100° 1:02 atmospheres, at —58° 2 atmospheres, at 0° 6°10, and at 
52° 14:60. 
Carbonic acid, when the snow of Tu1LoRiER is melted (at —'72° Fahr.) 
and re-solidified by a bath of low temperature, appears asa clear trans- 
parent, crystalline, colorless body, like ice—so clear as to deceive the 
eye ; it is heavier than the fluid bathing it, and has at —70° or —72°a 
pressure of 5°33 atmospheres. M. Cacniarp DE ta Tour has shown 
that, at a certain temperature, and under a sufficient pressure, a liquid 
becomes clear transparent vapor, or gas, having the same bulk as the 
liquid. At this temperature, or one a little higher, it is not likely that 
any additional pressure, however great, would convert the gas into a 
liquid. Mr. Faraday thinks that this state comes on with carbonic acid 
at about 90° Fahr. Mr. F. obtained the following pressures from car- 
bonic acid by his recent experiments : 
Fahr. Atmospheres. Fahr. Atmospheres. 
—111° 1-14 — 15° 17-80 
—107 1:36 0 22°84 
— 95 2°28 4 21:48 
— 83 - 3:60 5 24°79 
— 75 4:60 10 26°84 
— 56 7°70 15 29:09 
— 34 12°50 23 33°15 
— 23 15°45 a2 38°50 
‘Euchlorine is easily converted into a solid crystalline body, having 
the color and general appearance of bichromate of potassa. At 75° 
below 0° it melts into an orange-red fluid, in which the solid part sinks. 
It gives off no vapor when solid. 
Nitrous oxide was obtained as a beautiful, clear, crystalline solid at 
about —150°, and then had a pressure of less than one atmosphere. 
The cold produced by its evaporation is very great, and in certain cases 
it seems probable that this substance may be employed in procuring 
degrees of cold far below any yet obtained. Its vapor has the same 
irregularity of pressure, which was found in olefiant gas, and it seems 
probable that two substances are present, one more volatile than the 
other. At —40° its pressure is 10°20, at 0° 19-05, at 30° 85-82 atmos- 
pheres respectively. 
