charcoal

Black, porous form of carbon, produced by heating wood or other organic materials in the absence of air. It is used as a fuel in the smelting of metals such as copper and zinc, and by artists for making black line drawings. Activated charcoal has been powdered and dried so that it presents a much increased surface area for adsorption; it is used for filtering and purifying liquids and gases - for example, in drinking-water filters and gas masks.

Charcoal was traditionally produced by burning dried wood in a kiln, a process lasting several days. The kiln was either a simple hole in the ground, or an earth-covered mound. Today kilns are of brick or iron, both of which allow the waste gases to be collected and used. Charcoal had many uses in earlier centuries. Because of the high temperature at which it burns (1,100°C/2,012°F), it was used in furnaces and blast furnaces before the development of coke. It was also used in an industrial process for obtaining ethanoic acid (acetic acid), in producing wood tar and wood pitch, and (when produced from alder or willow trees) as a component of gunpowder.