What comes out of the blast furnace?

In addition to iron, the furnace produces slag and gas. The film describes the uses to which all three can be put. Explains that the object of the blast furnace is the smelt iron, but in the process other things are also produced, such as slag which collects in the hearth of the furnace together with the hot metal, and gas, which passes out of the top of the furnace. Shows how these products are treated and the uses to which they are put. Makes the point that very little is allowed to go to waste in a modern iron works.