ON THE DOCTRINE OF PHLOGISTON. 43 



•« or nothing etfe but water?" when not a particle of water thing by heat 

 is to be feen during the revival, or partial revival, of the me- with calx as with 

 tals from their oxide* in clofe veffels. Let us, however, con- 

 fider this fuppofition in another point of view ; which is, that 

 if water only were contained in thefe oxides, then the gas ob- 

 tained from a mixture of them and charcoal, (hould be the very 

 fame as that procured from moiftened charcoal ; but the con- contrary to facl, 

 trary of this I have clearly proved to be the cafe (fee Phil. 

 Journal, vol. v. quarto, p. 6.) ; and this was one of the princi- 

 pal faults which led to the difcovery of the gafeous oxide. 



I fhall herejuft enumerate a few of the properties by which Enumeration of 

 thefe gafes may be readily diftinguilhed, being deduced from a c ific r g ravity of 6 " 

 number of experiments, often repeated with uniform refults. gafeous oxide of 

 Firit, then, the fpecific gravity of the gafeous oxide of carbon ^at of hvarot 

 is no lefs than double that of the gas obtained from moiftened carbonate j 

 charcoal, being as 30 to 14.5. Secondly, The proportion of faturating oxigen 

 oxigen neceflary to faturate the gafeous oxide, is to that re- very dl erent \ 

 quired by the hydrocarbonate as 15 to 44.8, or 1 to 3, nearly 

 eftimating by quantity. And, thirdly, which is the moft dif- and produ£s of 

 tinguifliing property of the whole, the fame quantity of oxigen, ca . rb h °,"£ acld 

 fuppofe 14 parts, which, when combined with the gafeous ox- tions of oxigen. 

 ide of carbon, produces from 36 to 44 parts of carbonic acid 

 (according to the purity of the oxide), will, when combined to 

 faturation with the hydrocarbonate, produce only 12 parts of 

 the fame acid, accompanied, however, with much water, pro- 

 ceeding in part from the hidrogen in the charcoal, of which all 

 common charcoal, it would appear, contain a certain propor- 

 tion (fee P. Jour. No. 55. p. 210 and 211, and alfo the Table 

 of Analyfis, &c. p. 8. No. 59.) Surely gafes having proper- 

 ties fo eflentially different, can never be considered as the fame. 



Dr. Prieftley remarks, that there is a considerable difference Differences in. 

 in the qualities of heavy inflammable air, depending not only heav y inflam 7 

 on the fubftance employed, but alfo on the ftages or periods of by Dr. prieftley, 

 the procefs itfelf *. Now I have found that thefe variations 

 never take place in any remarkable degree but when charcoal are found only 

 is employed in fome form, and that even then the differences wh * n charcoal « 

 chiefly depend upon the imperfect ftate of the charcoal ; for if and mo'reor lefs 

 good charcoal be expofed to a red heat in clofe veffels during 5m P u re> 

 10 or 15 minutes, and then mixed whiht hot with the fubftance 



• P. Journ. No. 3. (Oa.) p. 183. 



to. 



