VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 223 



received a considerable addition of combustible matter, the oxygen employed was 

 only 4.0Q. To the rest of Dr. Austin's experiments either one or both of the 

 above objections are applicable. 



The first and most important step therefore, in the repetition of these experi- 

 ments, is to determine, whether the carbonated hydrogenous gas really sustains, 

 by the process of electrization, a diminution of its quantity of carbon; because, 

 should this be decided in the negative, we derive from the fact a very useful direc- 

 tion in ascertaining the true source of the evolved hydrogen. The following ex- 

 periments were therefore made with a view to decide this question, and the error 

 of Dr. Austin, in employing too little oxygen, was carefully avoided.* 



Exper. 1 . In a bent tube, standing inverted over mercury, 94.5 measures of 

 carbonated hydrogenous gas, from acetite of pot-ash, were mixed with 107.5 of 

 oxygen. The total, 202, was reduced by an explosion to 128.5, and was further 

 contracted by lime-water to 54. A solution of hepar sulphuris left only 23 mea- 

 sures. The diminution by lime-water, viz. 74.5 measures, makes known to us 

 the quantity of carbonic acid afforded by the combustion of 94.5 measures of car- 

 bonated hydrogenous gas: and the residue after the action of hepar sulphuris, viz. 23 

 measures, gives the proportion of azotic gas contained in the carbonated hydrogen j 

 for the oxygenous gas employed, which was procured from oxygenated muriate of 

 pot-ash, was so pure, that the small quantity used in this experiment could not 

 contain a measurable portion of azotic gas. 



Exper. 2. The same quantity of carbonated hydrogen was expanded, by repeated 

 electrical shocks, to 188 measures. The addition of hydrogenous gas therefore 

 amounted to 93.5. The gas thus dilated was fired, at different times, with 392.5 

 measures of oxygenous gas; and the residue, after these several explosions, was 203 

 measures. Lime water reduced it to 128.5, and sulphureof pot-ash to 19.5. In 

 this instance, as in the former one, the product of carbonic acid is 74.5 measures. 

 Finding, from the first experiment and other similar ones, that the carbonated hy- 

 drogenous gas, which was the subject of them, contained a very large admixture 

 of azotic gas, I again submitted to distillation a quantity of the acetite of pot-ash, 

 with every precaution to prevent the adulteration of the product with atmospherical 

 air. Such an adulteration, I have observed, impedes considerably the dilatation of 

 the gas, and for a time even entirely prevents it. This explains the failure, which 



* The apparatus employed in these experiments, was the ingenious contrivance of Mr. Cavendish 

 and is described in vol. 75, of the Philos. Trans. In dilating the gas, I sometimes used a straight tube, 

 furnished with a conductor, in the manner of Dr. Priestley, (see his Experiments on Air, vol. 1, plate 

 1, fig. 16.) The bulk of the gases introduced, and their volume after the various experiments, were 

 ascertained by a moveable scale, and by afterwards weighing the mercury which filled the tube to the 

 marks on the scale ; by which means I was spared the trouble of graduating the syphons. Each grain 

 of mercury indicates 1 measure of gas ; and though the smallness of the quantities submitted to experi- 

 ment may be objected to, yet this advantage was gained, that the electrified gas could be fired at one 

 explosion, as was done in the 4th, 6th, and 8th experiments. Errors, from variations of temperature 

 and atmospherical pressure, were carefully avoided. — Orig. 



