232 Chemistry. [Lecture 32. 



may be reduced by tin, iron, or zinc. Brim- 

 stone may be reproduced by silver, lead, tin, 

 copper, &c. 



When small quantities of metallic calces are 

 to be reduced, the Hack flux, as it is called, is 

 generally used. It has its name from its colour, 

 which arises from a quantity of charcoal it con- 

 tains, and from the property of fluxing or bring- 

 ing metallic oxides or earths easily into fusion. 

 Such a heat should be applied as will loosen the 

 particles of the charcoal from one another, for 

 this will promote the reduction. This method 

 is used in reducing small quantities, as in assay- 

 ing of ores, but would be too expensive when 

 much is to be reduced. They then mix the 

 oxides or ores with the fuel, and apply a strong 

 heat, but let as little air as possible pass through 

 the fuel ; because if air was admitted, it would 

 of course bring a quantity of oxygen with it, 

 which would prevent the reduction. For this 

 purpose, therefore, a particular sort of furnace 

 has been constructed, in which the charcoal of 

 wood is most used ; but when metals are much 

 oxidized, we do not find that we can recover the 

 whole of the original metal by this operation, 

 for there is always a portion of it lost. 



The metals combine also with the simple 

 combustibles, and the termination uret is added 

 to the name of the combustible, to denote the 

 combination. Thus we have a phosphuret, a 



