Sodium silicate is the common name for compounds with the formula Na₂(SiO₂)_nO. A well-known member of this series is sodium metasilicate, Na₂SiO₃. Also known as waterglass or liquid glass, these materials are available in aqueous solution and in solid form. The pure compositions are colourless or white, but commercial samples are often greenish or blue owing to the presence of iron-containing impurities.