Sodium silicate

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Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. The general formula for sodium silicate is Na₂SiO₃, although it can vary in ratios, leading to various forms of the compound. It is a colorless, water-soluble substance that can form a gel-like paste when mixed with water, and it is used in a wide range of applications, from industrial to household uses.

Production

Sodium silicate is produced by melting high purity sand with sodium carbonate (soda ash) at high temperatures. This process yields a variety of sodium silicate compounds, depending on the specific ratio of silica to sodium oxide used. The resulting liquid sodium silicate is then cooled and sold either as a solid lump, or more commonly, as a thick liquid.

Properties

Sodium silicate solutions are alkaline in nature. When dissolved in water, they can form solutions with a wide range of viscosities, which can be adjusted according to the concentration and temperature. This versatility makes sodium silicate useful in a variety of industrial and commercial applications.

Applications

Adhesives

Due to its adhesive properties, sodium silicate is used as a binder in cements and refractory materials. It is also used in cardboard, paper-making, and as a general-purpose adhesive for porous materials.

Detergents

In the production of detergents, sodium silicate is used as a builder to enhance cleaning efficiency. It helps in the emulsification of oils, stabilization of the detergent formula, and prevention of corrosion in washing machines.

Water Treatment

Sodium silicate is used in water treatment as a corrosion inhibitor and to help remove impurities. It forms a protective layer on metal surfaces, preventing rust and corrosion.

Foundry

In foundry work, sodium silicate is used as a binder for sand molds. When mixed with sand and heated, it hardens, forming a mold that can withstand the pouring of molten metal.

Other Uses

Other applications include the stabilization of soils, fire protection, the manufacture of silica gel, as a catalyst support, and in the synthesis of zeolites.

Health and Safety

While sodium silicate is generally considered safe, it can be irritating to the skin, eyes, and respiratory system upon contact or inhalation of dust. Proper safety precautions, such as wearing gloves and masks, should be taken when handling sodium silicate.

Environmental Impact

Sodium silicate is considered to have a low environmental impact. It is non-toxic and biodegradable, breaking down into harmless silica and sodium ions by natural processes.