MINERALS AND ORES 



169 



o 



which, by solution, remove the metaj from the ore. If heat 



is to be the chief reducing agent, the ore may be used in 



larger lumps. These lumps are 



put into a tall, cylindrical blast 



furnace. A blast furnace is 



made in such a way that a 



powerful blast of air can be 



forced through it to secure rapid 



combustion and therefore a very 



high temperature. 



The reduction of iron is ac- 

 complished as follows: Layers 

 of coal or coke, ore, and lime- 

 stone are built up within the 

 furnace to about two thirds its 

 height, and the fuel is ignited. 

 Since the fuel and ore are ar- 

 ranged in layers, the fire is not 

 confined to the bottom of the 

 furnace, but extends all through 

 the mass. On the top, as the 

 mass settles down, new material 

 is added from time to time. 

 The rock material of the ore 

 and the limestone, which is 

 called a flux, melt and unite 

 to form a glass-like substance, F IG> 34. _ A BLAST FURNACE 

 known as slag. w = wall Hned ^ fire day . 



When the rock has been / and o = fuel, flux, and ore; 



separated from the. ore, what U^oX^^odtS 



remains is chiefly the Oxide waste gases which are used to heat 

 Of iron. The heating is COn- the air blast 6, which enters near 



the base; s = slag; m = melted 



tinued, and the hot carbon of iron. 

 the fuel unites with the oxy- 



gen of the iron Oxide, forming nace, whence they are drawn out. 



