634 PHILOSOPHICAL TRANSACTIONS. [aNNO 1790. 



Dr. A. therefore attempted to decompose the heavy inflammable air by means 

 of sulphur, which readily unites with the light inflammable air in a condensed 

 state, and with it forms hepatic air. Having introduced some sulphur into a 

 retort, filled with heavy inflammable air, and applied a sufficient heat to melt 

 and sublime it, a considerable quantity of hepatic air was formed. After this 

 air was absorbed by water, he could not perceive that the remaining air differed 

 from the heavy inflammable air before the operation. Sulphur mixed with pow- 

 dered charcoal, on being heated, yields hepatic air in great abundance, almost 

 the whole of which is absorbed by water. The small unabsorbed residue, which 

 does not exceed 100th part of the bulk of the whole air, appears to be phlogis- 

 ticated air. 



In whatever manner the heavy inflammable air was decomposed, whether by 

 passing the electrical spark through it, by melting sulphur in it, or by heating 

 sulphur and charcoal together, an appearance constantly occurred, which seemed 

 to indicate, that volatile alkali is formed, whenever the heavy inflammable air is 

 decomposed. The circumstance is this ; a small piece of paper, stained with 

 any blue vegetable substance, is turned green by standing in the air during any 

 of these processes ; and this green is changed to red on the addition of an acid. 

 The inflammable air had been very long exposed to water, and had no such 

 effect on blue vegetable substances before the operation. The Dr. has con- 

 cluded these analytic attempts with several observations on the formation of 

 fixed air from some substances, which consist only of the light inflammable, 

 phlogisticated, and dephlogisticated airs, and from others, in which these 3 

 airs are combined with such matters as cannot be suspected of having any place 

 in the composition of fixed air. He then gives a detail of the experiments on 

 which these observations are founded. After which he adds : notwithstanding 

 the utmost attention, we are liable to a small error in each of these experiments ; 

 and there is consequently a small variation in the results ; but yet they concur 

 sufficiently to justify the following conclusions. 1. That the heavy inflammable 

 air contains the light inflammable air in great abundance. He apprehends this 

 light inflammable air was, before the application of the electrical spark, a con- 

 stituent part of the heavy inflammable air ; because, if it were contained in the 

 heavier air not as a constituent part, what should hinder its being burnt when 

 the heavy inflammable air is burnt? Can it be supposed, that the heavy inflam- 

 mable air should contain the light inflammable air in circumstances of combus- 

 tion, and that the light inflammable air should escape the fire ? And if the 

 lighter air be burnt, the same quantity of dephlogisticated air would be neces- 

 sary to saturate it before as after its being electrified. But it is evident from the 

 preceding experiments, that much more dephlogisticated air is necessary to satu- 

 rate the air, after it has been expanded by the electrical shock, than before. 



