On phlogiston. 461 



four ounce meafures of the air were abforbed, and after 

 this being again heated in hydrogenous gas, fix ounce 

 meafures of the air vanifhed. 



In all thefe experiments nothing but water was produc- 

 ed. The carbonic acid gas was not obtained, unlefs it 

 previoufly exifted in the calces. 



It is not however denied, that fixed air may be generat- 

 ed by heating a pure metallic calx, in a particular kind of 

 inflammable air. Thus it may be made by reviving red 

 precipitate in hydrogenous gas, obtained from expofing the 

 flowers of zinc and coal to a red heat, or from pafling alco- 

 hol over red hot iron, but none will be procured from that 

 made by the diluted fiilphuric acid and malleable iron, or 

 from that obtained by paffing the fleam of water over mal- 

 leable iron. 



Upon reviving three drachms of red precipitate, in thirty- 

 fix ounce meafures of hydrogenous gas, from the flowers 

 of zinc and coal, and which had been well wafhed in lime 

 water, there was an abforption of only two ounce meafures. 



After the operation, there was a great produftion of car- 

 bonic acid gas. Water was not formed in this procefs, 

 for the coal held in folution in the hydrogenous gas, had a 

 fl;ronger attraction to the pure, than to the inflammable 

 air, and confequently fixed air was generated. 



Had the fame quantity of precipitate been revived in in- 

 flammable air, from malleable iron, upwards of thirty 

 ounce meafures of the air would have vaniflicd. 



Dr. Prieftley, fuppofing that the inflammable air, or the 

 phlogirton it contains, emers into the compofition of the 

 metals, has made a calculation of the quantity of this air 

 abforbed by an ounce offeveralof them. He calculates 

 from the metal aftually revived. According to him, one 

 ounce of mercury abforbs three hundred and fixty-two ounce 

 meafures of hydrogenous gas. The quantity mentioned here, 

 iy far too great. One drachm of red precipitate, which con- 

 tains 



