190 Mr. Faraday on the condensation of 
sulphuric acid and sulphate of mercury, a portion was re- 
absorbed, but the rest remained on it without mixing. 
Liquid sulphurous acid is very limpid and colourless, and 
highly fluid. Its refractive power, obtained by comparing 
it in water and other media, with water contained in a similar 
tube, appeared to be nearly equal to that of water. It does 
not solidify or become adhesive at a temperature of o° F. 
When a tube containing it was opened, the contents did not 
rush out as with explosion, but a portion of the liquid evapo- 
rated rapidly, cooling another portion so much as to leave 
it in the fluid state at common barometric pressure. It was 
however rapidly dissipated, not producing visible fumes, but 
producing the odour of pure sulphurous acid, and leaving 
the tube quite dry. A portion of the vapour of the fluid 
received over a mercurial bath, and examined, proved to be 
sulphurous acid gas. A piece of ice dropped into the fluid 
instantly made it boil, from the heat communicated by it. 
To prove in an unexceptionable manner that the fluid was 
pure sulphurous acid, some sulphurous acid gas was care- 
fully prepared over mercury, and a long tube perfectly dry, 
and closed at one end, being exhausted, was filled with it ; 
more sulphurous acid was then thrown in by a condensing 
syringe, till there were three or four atmospheres ; the tube 
remained perfectly clear and dry, but on cooling one end to 
o°, the fluid sulphurous acid condensed, and in all its cha- 
racters was like that prepared by the former process. 
A small gage was attached to a tube in which sulphurous 
acid was afterwards formed, and at a temperature of 45° F. 
the pressure within the tube was equal to three atmospheres, 
there being a portion of liquid sulphurous acid present : but 
