Sodium silicate
Versatile industrial compound used as adhesive, binder, and coagulant.
Sodium silicate is a generic name for chemical compounds with the formula Na2xSiyO2y+x or (Na2O)x·(SiO2)y, such as sodium metasilicate, sodium orthosilicate, and sodium pyrosilicate. These compounds are generally colorless transparent solids or white powders, soluble in water, and are also known as waterglass or liquid glass. The commercial product has a wide variety of uses, including adhesives, coatings, water treatment, and refractory ceramics.
- chemical_formula
- Na2xSiyO2y+x or (Na2O)x·(SiO2)y
- common_name
- Waterglass, water glass, liquid glass
- appearance
- Colorless glassy or crystalline solids, white powders, or greenish/blue solutions
- solubility
- Readily soluble in water (except most silicon-rich grades)
- SiO2:Na2O_ratio_range
- 1:2 to 3.75:1
- maximum_temperature_resistance
- Up to 1100 °C
- global_production_1990
- 4 million tons of alkali metal silicates
Lore & Background
Sodium silicate is produced by treating a mixture of silica (usually as quartz sand), caustic soda, and water with hot steam, or by dissolving silica in molten sodium carbonate. It can also be obtained from sodium sulfate with carbon as a reducing agent. In 1990, 4 million tons of alkali metal silicates were produced. The material is also a byproduct of the Bayer process and can be produced during hydrogen production by dissolving ferrosilicon in aqueous sodium hydroxide.
Reader's Guide
Sodium silicate's significance lies in its broad industrial utility. Its adhesive properties were noted as early as the 1850s and have been widely used since the First World War, particularly as a cement for cardboard. In foundries, it serves as a binder for sand casting, hardened by carbon dioxide, esters, or microwave energy. In water treatment, it acts as a coagulant, binding colloidal molecules to form larger aggregates. Its use in passive fire protection, refractory ceramics, and as a deflocculant in pottery casting slips further demonstrates its versatility. The compound's ability to form silica gel when heated makes it valuable as a desiccant. Despite its advantages, sodium silicate joints in paper cement tend to crack within a few years, and its use in glass bonding can be hindered by air bubbles.
Did You Know?
- Sodium silicate is also called waterglass, water glass, or liquid glass.
- The commercial product is often greenish or blue due to iron-containing impurities.
- Sodium silicate can withstand temperatures up to 1100 °C.
- It is used as a binder in sand casting, hardened by carbon dioxide gas, esters, or microwave energy.
More in Sodium Compounds 1-24
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