1824.] Liquefaction of Chlorine and other Gases. 93 



Sulphurous Acid. 



Mercury and concentrated sulphuric acid were sealed up in a 

 bent tube, and, being brought to one end, heat was carefully 

 applied, while the other end was preserved cool by wet bibulous 

 paper. Sulphurous acid gas was produced where the heat acted, 

 and was condensed by the sulphuric acid above ; but, when the 

 latter had become saturated, the sulphurous acid passed to the 

 cold end of the tube, and was condensed into a liquid. When 

 the whole tube was cold, if the sulphurous acid were returned 

 on to the mixture 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 soli- 

 dify or become adhesive at a temperature of 0° F. When a tube 

 containing it was opened, the contents did not rush out as with 

 explosion, but a portion of the liquid evaporated rapidly, cooling 

 another portion so much as to leave it in the fluid state at com- 

 mon 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 exa- 

 mined, proved to be sulphurous acid gas. A piece of ice drop- 

 ped into the fluid instantly made it boil, from the heat communi- 

 cated by it. 



To prove in an unexceptionable manner that the fluid was pure 

 sulphurous acid, some sulphurous acid gas was carefully pre- 

 pared 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 0°, the fluid sulphurous acid con- 

 densed, and in all its characters 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 pres- 

 sure within the tube was equal to three atmospheres, there being 

 a portion of liquid sulphurous acid present : but as the common 

 air had not been excluded when the tube was sealed, nearly one 

 atmosphere must be due to its presence, so that sulphurous acid 

 vapour exerts a pressure of about two atmospheres at 45° F. Its 

 specific gravity was nearly 1*42. # , 



• I am indebted to Mr. Davics Gilbert, who examined with much attention the 

 results of these experiments, for the suggestion of the means adopted to obtain the spe- 

 cific gravity of some of these fluids. A number of small glass bulbs were blown and 

 hermetically scaled ; they were then thrown into alcohol, water, sulphuric acid, or mix- 



