On phlogiston. 459 



I agree with the Dodor, that carbonic acid gas xvill be 

 obtained by reviving minium, or mercurius prccipitatus 

 per fe in inflammable air, for thele calces generally contaia 

 it, but if the minium be converted into mafficot, no fixed 

 air w^ill be generated. 



Here we have a ftrong proof of the pofition we are 

 endeavouring to eftablifh. 



Two drachms of red lead, make twenty ounce meafures 

 of inflammable air difappear, when heated in it by the 

 burning lens, but when converted into mafficot, only eight 

 ounce meafures. 



Now, if Dr. Prieftley's theory was true, that the metal 

 imbibed the air, mafficot ought to abforb more inflammable 

 air than minium, as it contains more lead than an equal 

 weight of minium. 



In making red lead into mafficot, nothing but pure air 

 with a fmall quantity of fixed air efcapes, and the lofs of 

 the pure air is the true reafon, that one calx of the fame 

 metal, will make more inflammable air difappear than 

 another. 



But we have ftill ftronger proofs, to prove that our ideas 

 on this fubjedl arc juft. 



The focus of the lens was thrown upon one drachm of 

 the oxyd of manganefe, confined in thirty ounce meafures 

 of hydrogenous gas, when twenty-two ounce meafures of 

 the gas difappeared, and the metal was not revived. How 

 then could the inflammable air have entered into its com- 

 pofition ? 



A quantity of the oxyd of manganefe, was expofcd to 

 a red heat for three hours, and a part of its pure air was 

 driven off", when upon throwing the focus of the lens upon 

 one drachm of it confined in inflammable air, none of the 

 air difappeared, whereas if this quantity of the oxyd, had 

 not been expofed to a red heat, twenty- two ounce mea- 

 fures of the air would have vanifhed. 



3 O 2 Some 



