90 On the Condensation [1823, 



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 unexceptional 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 sulphu- 

 rous 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 sulphu- 

 rous acid condensed, and in all its characters was like that pre- 

 pared by the former process. 



A small gauge 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 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 atmo- 

 spheres at 45 F. Its specific gravity was nearly 1*42*. 



Sulphuretted Hydrogen. A tube being bent, and sealed at 

 the shorter end, strong muriatic acid was poured in through a 

 small funnel, so as nearly to fill the short leg without soiling 

 the long one. A piece of platinum foil was then crumpled up 



" * I am indebted to Mr. Davies Gilbert, who examined with much attention 

 the results of these experiments, for the suggestion of the means adopted to 

 obtain the specific gravity of some of these fluids. A number of small glass 

 bulbs were blown and hermetically sealed ; they were then thrown into alco- 

 hol, water, sulphuric acid, or mixtures of these, and when any one was found 

 of the same specific gravity as the fluid in which it was immersed, the specific 

 gravity of the fluid was taken : thus a number of hydrometrical bulbs were 

 obtained ; these were introduced into the tubes in which the substances were 

 to be liberated ; and ultimately, the dry liquids obtained, in contact with them. 

 It was then observed whether they floated or not, and a second set of experi- 

 ments were made with bulbs lighter or heavier as required, until a near ap- 

 proximation was obtained. Many of the tubes burst in the experiments, and 

 in others difficulties occurred from the accidental fouling of the bulb by the 

 contents of the tube. One source of error may be mentioned in addition to 

 those which are obvious, namely, the alteration of the bulk of the bulb by its 

 submission to the pressure required to keep the substance in the fluid state. 



