•ilS Mr. Faraday on the Condefisatioii 



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 sulphui'ous acid present : but 

 as the common air had not been excluded when the tube Mas 

 sealed, neai'ly one atmosphere must be due to its presence ; so 

 that sulpluu'ous acid vapour exerts a pressui'e of about two 

 atmospheres at 4-5° F. Its specific gravity was nearly 1'4'2.* 



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 and pushed in, 

 and upon that were put fragments of sulphuret of iron, until 

 the tube was nearly full. In this way action was prevented 

 until the tube was sealed. If it once commences, it is almost 

 impossible to close the tube in a manner sufficiently strong, 

 because of the pressing out of the gas. When closed, the 

 muriatic acid was made to run on to the sulphuret of iron, 

 and then left for a day or two. At the end of that time, much 

 proto-muriate of iron had formed, and on placing the clean 

 end of the tube in a mixture of ice and salt, warming the other 

 end if necessary by a little water, sulphuretted hydrogen in 

 the liquid state distilled over. 



The liquid sulphuretted hydrogen was colourless, limpid, 

 and excessively fluid. Ether, when compared with it in si- 

 milar tubes, appeared tenacious and oily. It did not mix with 

 the rest of the fluid in the tube, which was no doubt saturated, 

 but remained standing on it. When a tube containhig it was 

 opened, the liquid immediately rushed into vapour ; and this 

 being done under water, and the vapour collected and exa- 

 mined, it proved to be sulphuretted hydrogen gas. As the 



* I am indebted to Mr. Daxaes Gilbert, who examined with much atten- 

 tion 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 

 chrown into alcohol, 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 hy- 

 drometrical bulbs were obtained ; these were introduced into the tubes in 

 which the substances were to be liberated; and ultimately, the dry liquids 

 obtaiued, in contact with them. It was then observed whether they floated 

 or not, and a second set of experiments were made with bulbs ligiiter or 

 heavier as required, until a near approximation was obtained. Slany 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 tiie bulk of tlie bulb by its submission to the pressure re- 

 quired to keep the substance in the fluid state. 



temperature 



