164 



DR. FARADAY ON THE LIQUEFACTION AND SOLIDIFICATION OF 



Sulphurous acid. — When liquid, it dissolves bitumen. It becomes a crystalline, 

 transparent, colourless, solid body, at —105° Fahr. ; when partly frozen the crystals 

 are well-formed. The solid sulphurous acid is heavier than the liquid, and sinks 

 freely in it. The following is a table of pressures in atmospheres of 30 inches mer- 

 cury, of which the marked results are from many observations, the others are in- 

 terpolated. They differ considerably from the results obtained by Bunsen*, but 

 agree with my first and only result. 



Sulphuretted hydrogen. — This substance solidifies at 122° Fahr. below 0°, and is 

 then a white crystalline translucent substance, not remaining clear and transparent 

 in the solid state like water, carbonic acid, nitrous oxide, &c., but forming a mass 

 of confused crystals like common salt or nitrate of ammonia, solidified from the 

 melted state. As it fuses at temperatures above —122°, the solid part sinks freely 

 in the fluid, indicating that it is considerably heavier. At this temperature the press- 

 ure of its vapour is less than one atmosphere, not more, probably, than 0*8 of an atmo- 

 sphere, so that the liquid allowed to evaporate in the air would not solidify as car- 

 bonic acid does. 



The following is a table of the tension of its vapour, the marked numbers being 

 close to experimental results, and the rest interpolated. The curve resulting from 

 these numbers, though coming out nearly identical in different series of experiments, 

 is apparently so different in its character from that of water or carbonic acid, as to 

 leave doubts on my mind respecting it, or else of the identity of every portion of the 

 fluid obtained, yet the crystallization and other characters of the latter seemed to 

 show that it was a pure substance. 



* Bibliotheque Universelle, 1839, xxiii, p. 185. 



