Physical Properties of Sodium Silicate

Updated July 19, 2017

A reaction at very high temperatures between sodium carbonate and silicon dioxide forms the compound sodium silicate. Commonly known as water glass, sodium silicate is typically available in an aqueous solution, but you can also find it in solid state. As a gel, sodium silicate is used aquaculture as an effective substrate for algal growth. It is widely used in the automotive industry, in textile and lumbering processing, for fire protection and to make cements.


The appearance of sodium silicate is subject to several variations, depending on the intended application of the compound. The compound primarily appears as a white crystal powder and is commonly dissolved in water to form an alkaline solution. This solution has the glossy, colourless appearance of glass, hence the nickname water glass.


Sodium silicate has a high solubility in water and maintains stability while in neutral or alkaline solutions. The more acidic the solution becomes, the more reactive the silicate ions become with available hydrogen ions. The result is the production of silicic acid, commonly used in a hard, glassy substance called silica gel.

Substance Properties

The molar mass, or mass per amount of given substance, of sodium silicate is 122.06 grams per mole. It has a density of 2.4 grams per mole, with an extremely high melting point of 1088C. The automotive industry uses a hydrated form of sodium silicate called pentahydrate sodium silicate, which melts down at 72C.

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About the Author

Matt Badger has been writing professionally since 2010, contributing to various websites. Badger has a Bachelor of Science in biology from the University of Washington.