28 On the doctrine 



No. IV. 



Mifcellaneous Experiments reluting to the DoBrlne of 

 Phlog'ijlon. By Dr. Joseph Priestlly. 



I. TT has been faid that the fixed air which I get 

 A by "heating iron in dephlogifticated air, comes 

 from the phimbago contained in the iron, and that when 

 it is found after the union of inflammable and dephlogiiti- 

 cated air, it was from plumbago diiTolved in the inflam- 

 mable air. But befides that there is no evidence of inflam- 

 mable air containing any plumbago (ilnce when iron is 

 diflolved in any acid the plumbago is left behind) the fix- 

 ed air contained in this fubft:ance is very inconliderable, 

 the bulk of the air into which it may be refolved being 

 inflammable. 



From 6 dwts. of the finefl: plumbago from an iron 

 furnace, in the form of a light powder, I got in a glazed 

 earthen tube 40 ounce meafures of air, one-twelfth part 

 only of which was fixed air, and the refl: inflammable, 

 burning with a blue flame. Then fending fleam through 

 it, I got 240 ounce meafures more, the whole of which 

 was inflammable, of the purefl: kind, exa£lly refembling 

 that from iron by the acid of vitriol. The plumbago 

 was concreted into one mafs, refembling a hard cinder, 

 and weighed 2^ dwts. 



Another experiment on plumbago I fliall mention in 

 this place. Melting one dwt. of it with a burning lens, it 

 threw out fparks, like caft iron treated in the fame man- 

 ner, but not quite fo much ; after which it was reduced 

 to a fl;ig, like finery cinder, weighing 4 grains lefs than 

 it had done. I repeated the experiment with the fame 

 refult. 



2. The 



