Cast Iron^ Steely and Malleable Iron. 423 



{b.) The remaining 73-78 parts of graphite consisted of 



Carbon 70*34.21 



Silicon 3-0744. 



Loss 00*3635 



73-7800 

 and corresponds to 4-16 per cent, silicon. 



As it was impossible to extract the silica with caustic and 

 carbonaceous lyes, even after a week's digestion, and as the 

 silicon cannot be considered as silica without our obtaining an 

 improbable surplus in weight, we may safely conclude, that sili- 

 con existed as siich^ in the graphite, and in chemical combina- 

 tion with it; therefore we may assume graphite to be a super- 

 carburet of silicon^ in which about 86 atoms of carbon are 

 combined with one atom of silicon. 



Graphite {b) gave a dissimilar result. It retained, even 

 after the longest treatment with acids and alkalies, its first form 

 of elastic dull leaves of considerable thickness, and was found 

 to consist in 100 parts of 



Silicon 4-93 



Iron 9-50 



Carbon 85*45 



Loss 00*12 



100*00 

 It is scarcely necessary to remark that the relation of rfie 

 silicon to the iron when combined with oxygen in graphite 



(b) very nearly resembles the formula F^ S'^, that is, a sesqui- 

 silicate of iron resembling the composition of puddling slag; 

 and that graphite [a) may be considered as a compound of 

 carburet of iron with the carburet of silicon. 



This curious generation of graphite, only by the interference 

 of silicon and manganese, from the volatile matters of coal, 

 seems to afford us some hints towards explaining the origin of 

 graphite in blast furnaces, which is in all probability formed in 

 like manner, particularly as I observed that graphite is never 

 generated in melting pots from pure iron and pure carbon, 

 except when the black oxide of the surface began to attack 

 the sides of the crucible. 



That graphite makes its appearance in blast furnaces in the 

 highest degrees of heat, is not that it is only generated in this 

 highest degree of heat, but that it cannot exist without a quan- 

 tity of alumina being first reduced and combined with the 

 iron. 



The volatile parts of coal, and particularly tar, a combina- 

 tion of pyrretin with ammonia, exerts its reducing power over 



