Sodium metasilicate pentahydrate, commonly known as instant water glass, is an inorganic salt product. It is a non-toxic, odorless, and pollution-free white powder or crystalline granules. It is easily soluble in water, insoluble in alcohol and acid, and is hydroscopic. Its aqueous solution is alkaline and easily absorbs moisture and deliquesces in air. It has strong detergency, emulsification, dispersion, wetting, and permeability, and has pH buffering capacity. It can neutralize acidic dirt, emulsify fats and oils, deflocculate inorganic substances, and has anti-corrosion properties on metals. Among sodium metasilicate varieties, sodium metasilicate pentahydrate is the most widely used and typical. Its crystalline molecular formula is usually written as Na2SiO3·5H2O. Sodium metasilicate pentahydrate has the general properties of sodium silicate and sodium metasilicate, and has a certain calcium and magnesium ion binding capacity. In particular, its magnesium ion binding capacity is greater than 260mgMgCO2/g (35°C, 20min). Because it provides excellent buffering alkalinity in detergents, it offers corrosion protection for light metals (such as aluminum and zinc) and glassware and porcelain. It also suspends and emulsifies dirt and softens water to a certain extent.

It is widely used in household laundry detergents, laundry pastes, industrial detergents, food cleaners, metal cleaners, textile treatment, and paper deinking. It is an important additive in concentrated detergents, as well as phosphate-free and low-phosphate detergents. It is also used in the ceramic and petroleum industries. It is a white, square crystal or spherical particle that is non-toxic and odorless. It is easily soluble in water but readily absorbs moisture and deliquesces when exposed to air. It has the ability to remove dirt, emulsify, disperse, wet, penetrate, and buffer pH. Concentrated solutions are corrosive to fabrics and skin.