2CO On the Component Paris of Iron-ftones. 



lied appearance, this principle would be found to be entirely 

 annihilated. 



Although the colour which iron-ftones aflume in torrefy- 

 ing intimately depends upon the degree of heat prefented to 

 them in the operation of burning, yet, by regulating this 

 agent in a proper manner, an accurate knowledge may be 

 formed, not only of the probable quantity of iron, but even 

 of its tendency to become carbonated in fmelting. The ex- 

 pullion of the water and acid leaves the combined earths 

 more expofed to determination. The fmall fpecula of filex 

 are diftinctly difcerned ; adhefion to the tongue develops the 

 prefence of clay; and lime is indicated by its aflTuming a 

 whitifh colour, either ftriated, or difleminated, approaching 

 towards the furface of the {tone. 



The laft method mentioned, namely, that of depriving a 

 given portion of ore of its iron, is the moft confonant to 

 truth and to the ideas of the manufacturer. Acids may he 

 ufed as a check upon the aflay by fufion ; but this intricate, 

 or rather this flow pro.cefs is chiefly reforted to by chemifts, 

 and feldom goes beyond the bounds of the laboratory. In 

 affaying by fufion, not only the quantity of iron may with 

 precifion be afcertained, but alfo the quality of crude-iron 

 likely to be produced from the ore, with the local proportions 

 of fuel in the large way. The earths formerly united with 

 the iron, now become fufed with thofe added for folvents. 

 Thefe float upon the furface of the extracted metal, and, 

 when cold, may afford information, from their colour ind 

 tranfparency, concerning the regulation of future propor- 

 tions upon a more extended, fcale. This fubject I fli.all more 

 minutely illufbate in a fubfequent paper on the affaying of 

 iron-ores by fufion. 



The burning cr torrefying of iron-ftones, known in the 

 large way by the. rather improper term of calcination, con- 

 iitU in expofing the ftone to a certain degree of heat in con- 

 tact with air, in order to difpel thofe fubftauces which it 



contains, 



