Oxides of Carlon and I Iron, 235 



pounded as to the alloy of foreign matter, and employed un- 

 der the same circumstances, to revive equal quantities of the- 

 same metallic oxide, Would in not be just to infer, that if 

 the quantities of metal were equal, so were the qualities of 

 the oxide ; and the reverse if a different result were obtained? 

 And does it not appear equally fair to deduce; that where the 

 greatest quantity of metal is revived, the appropriated oxide 

 is of superior quality ? The former deduction holds uni- 

 versally correct; but the latter, if admitted, would often 

 lead into error, particularly where the oxides exist in the 

 state of coal or coke. 



I was once of opinion that the carbonating powers of any 

 oxide depended upon the real quantity of combustible mat- 

 ter which it contained ; and that the substance found to 

 yield the largest portion of coal or coke, and to contain the 

 smallest portion of ashes, would, every thing else being 

 alike, revive the greatest quantity of metallic oxide ; or, 

 in other words, would be found to contain the largest quan- 

 tity of pure carbon, or diamond: but upon investigating 

 the nature and properties of a variety of carbonaceous oxides, 

 chiefly obtained by the distillation of pit coal, with a view 

 to fix an unerring list whereby to judge of coal fit for iron 

 making, it was found that not only this conclusion was 

 of itself erroneous, but that, in general, the very reverse of 

 this theory took place. It not only appeared that the car- 

 bonating powers of the oxide depended upon some other 

 cause, remote from the actual quantity of combustible mat- 

 ter, but that the process of distillation, or of coking, sub- 

 jected the oxide to new laws, the very reverse of what at 

 first view ought to have taken place. This, then, was at once 

 attributed to the state of oxidation of the oxide ; and a direct 

 probability inferred, that that coke or coal that revived the 

 greatest quantity of metallic oxide would be the least oxi- 

 dated ; or, in other words, approach more nearly to the state 

 of diamond. 



This theory, however plausible, was found incompatible 



with practice ; and in the event it was found that the cokf 



or coal that became most deoxidated in burning, revived, 



under precisely the same circymstances, the least quantity 



• . of 



