036 PHILOSOPHICAL TRANSACTIONS. [aNNO IJQO. 



lour ; as it sublimed, it became quite black, and every part of the retort was 

 covered with a black crust. On the depending part of the retort, where the 

 melted sulphur lodged, and where the heat was strongest, there remained a 

 black mark, which could not be removed by a much greater heat than that by 

 which the sulphur was sublimed. The bulk of the air was not materially 

 altered by this operation. A little blue paper being thrown up to the air after 

 the operation, became green. Water absorbed about ^ of it, and acquired a 

 strongly hepatic smell. The inflammable air was carefully washed, so as to sepa- 

 rate from it all the hepatic air. He then mixed this inflammable air with de- 

 phlogisticated air, and inflamed them, expecting to find a greater quantity of 

 phlogisticated air in the residue, than when the inflammable air was burnt, 

 which had not been subjected to this process. But the difference of the residue 

 does not exceed Vt ^^^ quantity of air decomposed in this manner, if we may 

 judge from experiment. 



The analogy between the heavy inflammable air and charcoal is illustrated by 

 the formation of hepatic air from charcoal and sulphur. These substances, 

 heated in a small glass retort, yield hepatic air in great abundance. The blue 

 vegetable colour is turned green by exposure to this air. After hepatic air had 

 been generated for a long time from the same materials, without admitting any 

 common air into the retort, 99 parts in 100 of the air which came over last 

 were absorbed by water. The insoluble part appeared to be phlogisticated air. 

 Thus sulphur and charcoal, heated in a glass retort, yield hepatic air, phlogisti- 

 cated air, and volatile alkali, or a substance very analogous to it. 



As far as the Dr. has been able to discover by experiments, the heavy inflam- 

 mable air and charcoal consist of the same elements in different proportion. The 

 application of heat to pure charcoal confirms this opinion ; for the production of 

 heavy inflammable air from charcoal, by mere heat, is constantly accompanied 

 with a production also of phlogisticated air. He apprehends, that in these cases 

 the charcoal is decomposed and resolved into these 2 parts. Whenever charcoal 

 or any substance containing it, is decomposed by heat only, the phlogisticated 

 and heavy inflammable airs are produced ; and when the heat is intense. Dr. 

 Higgins has observed, that the air produced from these substances becomes 

 rarer ; probably in consequence of a portion of the heavy inflammable air itself 

 being resolved by heat into its constituent parts. Dr. A. would not lay much 

 stress on the appearance of phlogisticated air from the compound forms of vege- 

 table, animal, and bituminous substances, all of which yield phlogisticated air 

 and volatile alkali in great abundance ; yet when the more simple modifications 

 of the heavy ^inflammable air, as charcoal, vinegar, and, if Dr. Priestley is not 

 mistaken, fixed air, give out phlogisticated air, when decomposed in close 

 vessels, he cannot but infer, that phlogisticated air is an essential part of that pe- 



