Potassium silicate

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Potassium silicate
Preferred IUPAC name
Potassium metasilicate
Other names
Liquid glass
3D model (JSmol)
ECHA InfoCard 100.029.989
EC Number 233-001-1
E number E560 (acidity regulators, ...)
Molar mass 154.279 g·mol−1
Appearance White crystals
Corrosive (C), Irritant (Xi)
R-phrases (outdated) R34, R37
S-phrases (outdated) (S1/2), S13, S24/25, S36/37/39, S45
NFPA 704
Flammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Other anions
Potassium carbonate
Potassium germanate
Potassium stannate
Potassium plumbate
Other cations
Sodium silicate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Potassium silicate is the name for a family of inorganic compounds. The most common potassium silicate has the formula K2SiO3, samples of which contain varying amounts of water. These are white solids or colorless solutions.[1]

Synthesis, structure, reactions[edit]

Potassium silicate can be synthesized in the laboratory by treating silica with potassium hydroxide, according to this idealized equation:

These solutions are highly alkaline. Addition of acids causes the reformation of silica.

K2SiO3 adopts a chain or cyclic structures with interlinked SiO32− monomers. Each Si is tetrahedral.


Woodwork protection against fire[edit]

Impregnation of wood with a potassium silicate solution is an easy and low cost way for rendering the woodwork of houses secure against catching fire. The woodwork is first saturated with a diluted and nearly neutral solution of potash silicate. After drying, one or two coats of a more concentrated solution are usually applied.[2]


In horticulture, potassium silicate is used as a soluble source of potassium and silicon. It makes the growing medium more alkaline.

It is also used as a supplement (in conjunction with normal fertilizer) for the numerous benefits that increasing the availability of silicon compounds has. Silicon-containing compounds are valuable to a plant, and serve to support the plant. Stems thicken, the plant becomes more tolerant to drought and resists wilting, and the plant gets larger leaves and fruit (because the stem can support more weight).[3] The thicker cell walls of the plant also provides an added mechanical resistance to sap sucking insects (e.g. spider mite) and various pathogenic fungi (e.g. powdery mildew).

Industrial uses[edit]

Some metal cleaning formulations use potassium silicate, which also serves as a corrosion inhibitor.[4] It also finds various uses in the fabrication of welding rods or even of cosmetics.


Potassium silicate is strongly alkaline.

See also[edit]


  1. ^ Gerard Lagaly, Werner Tufar, A. Minihan, A. Lovell "Silicates" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2005. doi:10.1002/14356007.a23_661
  2. ^ Cobleigh, Rolfe (1909). Handy farm devices and how to make them. Part II: Worth knowing to render wood fireproof. New York: Orange Judd.
  3. ^ S. Y. Wang & G. J. Galletta (1998) Foliar application of potassium silicate induces metabolic changes in strawberry plants, Journal of Plant Nutrition, 21:1, 157-167, doi:10.1080/01904169809365390
  4. ^ Elmore AR (2005). "Final report on the safety assessment of potassium silicate, sodium metasilicate, and sodium silicate". Int. J. Toxicol. 24 (Suppl 1): 103–17. doi:10.1080/10915810590918643. PMID 15981734.

External links[edit]