Sodium silicate, commonly known as water glass, is an ionic silicate of sodium. There are many compounds with the name "sodium silicate," but the most common is sodium metasilicate, Na2SiO3.
Sodium silicate dissolves easily in water, forming a basic solution. It tends to form high hydrates, such as the pentahydrate and nonahydrate. Most metal salt solutions yield metal silicates upon treatment with sodium silicate, some similar in composition to silicate minerals. Sodium silicate can also act as a flocculating agent or to increase the viscosity of a liquid mixture, as well as a component in some cements.
Sodium silicate forms glassy, colorless crystals.
Sodium silicate can be found at some chemical supply stores, though it may be easier to make it.
Sodium silicate can prepared by heating a sodium hydroxide solution with silica gel. A more dangerous method of preparation is to add plain glass scrap (not lead oxide glass or borosilicate glass) to molten sodium hydroxide. Rather than using glass, cleaned silica sand can be added instead. After thorough mixing of the silica into the sodium hydroxide(an excess of the silica is required to prevent sodium hydroxide in the product), the mass of reactants hardens, and can be leached with warm water to obtain a viscous solution of sodium silicate.
Sodium silicate is not particularly toxic, though it may contain free alkali and gloves should be worn when handling the protection.
Solid sodium silicate can be stored in closed containers. Silicate solutions should be stored at temperatures lower than 60°C, as higher temperatures tend to promote dehydration of the silicate, causing a surface skin to be formed.
Sodium silicate can be neutralized with an acid and since the byproducts are not toxic, they can be safely disposed of.