text: In industrial processes, the reduction of metal oxides is often effected by a carbothermic reaction, using carbon as a reducing agent. Carbon is available cheaply as coal, which can be rendered to coke. When carbon reacts with oxygen it forms the gaseous oxides  carbon monoxide and carbon dioxide, so the thermodynamics of its oxidation is different from that for metals: its oxidation has a more negative ΔG with the higher temperatures (above 700 °C). Carbon can thus serve as reducing agent. Using this property, reduction of metals may be performed as a double redox reaction at relatively low temperature.