Silicon monoxide

Silicon monoxide is a black powder that is insoluble in water but soluble in a mixture of dilute hydrofluoric acid and nitric acid. It reacts with boiling caustic soda solution to form silicates and hydrogen. It can be oxidized by halogens and its surface is easily oxidized in the air to form a silicon dioxide protective film, which makes it chemically inactive. It has strong reducing properties at high temperatures and can reduce substances such as water vapor, carbon dioxide, and limestone. It is often produced industrially by sublimation of silicon dioxide and elemental silicon powder in a high vacuum at above 1400°C. It is often used to prepare optical glass and semiconductor materials.