Silicon Carboxide

The compound (SiCO)_x is formed when silicon is heated to whiteness in an atmosphere of carbon dioxide:

3Si + 2CO₂ = SiO₂ + 2SiCO.

After the removal of silica with hydrofluoric acid the carboxide remains as a greenish white powder, which is stable towards alkalis.

A product called Siloxicon has been prepared by Colson, and is manufactured by the Acheson Company at Niagara, by heating a mixture of sand, powdered coke, and sawdust in the electric furnace to a temperature not exceeding 2800° C. The reaction is approximately

2SiO₂ + 5C = Si₂C₂O + 3CO,

but the product is a mixture, and may contain other bodies besides Si₂C₂O, e.g. C₇Si₇O, if the proportion of carbon to silica is varied. Siloxicon is refractory, and greyish green when cold, but light yellow above 300° F.; its density is 2.73, and it binds when ground with water and fired.