ON THE DOCTRINE OF PHLOGISTON. 47 



tlo it, &c. &c. ? But here he has forgotten that the affinities of 

 bodies are remarkably varied by change of temperature, and 

 that, in all reductions of metallic oxides, the carbon of the as it does In all 

 charcoal, when raifed to a high temperature, unites with the re u 

 oxigen of the calx in confequence of increafed affinity, and 

 forms with it carbonic acid gas and gafeous oxide. That this Red oxides of 

 is the cafe is remarkably proved by dialling the red oxides of^^^f* 

 mercury and lead with charcoal ; for thefe oxides we know acid and oxide, 

 contain a large proportion of oxigen, which may be feparated J^h^exral. 

 by heat alone, but when heated with charcoal, nothing but men ts. 

 carbonic acid and gafeous oxide come over, becaufe, in this 

 cafe, the whole of the oxigen being in its nafcent itate, com- 

 bines, even at a low temperature, with the charcoal, and paffes 

 over in the form of carbonic acid gas mixed with the gafeous 

 oxide. There are fome circumftances accompanying the dif- Dedu&ions. 

 tillation of charcoal with thefe metallic oxides, which are eafiiy 

 reduced, and at low temperatures, not altogether uninftructive, 

 and, in my opinion, unanfwerable by the fupporters of phlo- 

 gifton. In thefe procetTes the proportion of gafeous oxide to 

 carbonic acid gas is but fmall, being in general about one-third 

 or one-fifth of the whole, and for the molt part is obtained juft 

 before or at the time the mixture becomes red : It is always 

 accompanied with a torrent of carbonic acid gas. At the in- 

 ftant the metal is revived, the gas either ceafes entirely, or 

 comes over very flowly ; but on increafing the heat, it again 

 makes its appearance, and is now fo far from containing ga- 

 feous oxide, that it is peculiarly light, not mixed with any len- 

 fible quantity of carbonic acid gas, and yields, when faturated 

 with oxigen, but a very fmall proportion of this acid gas. 



The following fa6ls may be drawn from thefe experiments : 

 Firft, It would appear that a much greater degree of heat is 

 necefTary for the proper production of the gafeous oxide than 

 for the carbonic acid. Secondly, That oxigen, in its nafcent 

 ftate, may unite with carbon at lefs than a red heat, and form 

 carbonic acid ; as is clearly proved by the procefs with the red 

 oxide of mercury and charcoal. The galeous oxide appears 

 like wife to be produced at a very low heat. 



I have now taken a view of all the arguments which Dr. Concluficn, 

 Prieftley has brought forward in defence of his former opinions, 

 butfliall at prefent make no further observation on this fubjecl, 

 leaving the argument and fact to be decided by your philofophi- 

 cal and chemical readers.— I am, SIR, &c. 



X, AT 



