226 PHILOSOPHICAL TRANSACTIONS. [ANNO 1797. 



to a volume of the expanded gas, amounting to 556 measures, when they were 

 immediately reduced to 512. The contraction would probably have been still more 

 remarkable if the gas had been further expanded before the admission of the liquid. 

 Thecha-nge in the lime-water was very trifling; but my friend Mr. Rupp, who wit- 

 nessed this as well as several of the other experiments, and who is much conversant 

 in the observation of chemical facts, was satisfied that, after a while, he saw small 

 flocculi of a precipitate on the surface of the mercury. This contraction of bulk 

 cannot be ascribed to any other cause than the absorption of carbonic acid; for 

 besides the fact, that the colour of syrup of violets and of turmeric, which I also 

 tried, were not affected by exposure to the electrified gas, I have this objection to 

 the absorbed gas being ammonia, that no diminution, either of bulk or trans- 

 parency, occurred on the admixture of muriatic acid gas with the electrified air; 

 whereas ammonia would have been exhibited under the form of a neutral salt. 

 When water was passed up to this mixture of the 2 gases, there was an absorption, 

 not only of the muriatic gas, but of something more. 



Conceiving that the demolition of charcoal, by the action of the electric fluid, 

 was sufficiently proved by his experiments, Dr. Austin assigns the evolved hydrogen 

 as 1 of its constituents, and the other he concludes to be azote. This inference 

 however rests almost entirely on estimates, in which material errors may be dis- 

 covered. Some of these it may be well to point out, for the satisfaction of such 

 as have acquiesced in Dr. Austin's opinion. The carbonated hydrogenous gas sub- 

 mitted to Dr. Austin's experiments clearly appears, from his own account, to have 

 been largely adulterated with azotic gas. One source of its impurity he has dis- 

 closed, by informing us that the gas " had been very long exposed to water*;" for 

 Dr. Higgins has somewhere shown that the heavy inflammable air, after standing 

 long over water, leaves a larger residue of azote, on combustion, than when re- 

 cently prepared -j~. It is probable also, that the proportion of azote derived from 

 the water, would increase with the time of its exposure ; and thus a fertile source 

 of error is suggested, which appears wholly to have escaped Dr. Austin's attention. 

 In repeating his experiments, I was careful that comparative ones, on 2 equal 

 quantities of the electrified and unelectrified gas, should be made, without the in- 

 tervention of any time that could vary the proportion of azote in either of the 

 gases. 



To the Qth experiment, in which the quantity of azote seems to have been in- 

 creased by electrization, I must repeat the objection, that a sufficiency of oxygenous 

 gas was not used in the combustion. In the 8th experiment, 2.83 of the unelec- 

 trified air were fired with 4.17 oxygenous gas, and only 0.15 of the latter remained 

 above what was sufficient for saturation; but in the 9th, though the 2.83 measures 



* 80 Phil. Trans. 54. — f Similar facts respecting the deterioration of other gases, by standing over 

 water, may be seen in Dr. Priestley's Experiments on Air, vol. 1, p. 59, 158. I found that oxygenous 

 gas, from oxygenated muriate of pot-ash, acquired, by exposure a few weeks to water, .125 its bulk of 

 azotic gas. — Orig. 



