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Silicotungstic acid

Silicotungstic acid
Other names
Tungstosilicic acid
ECHA InfoCard 100.206.333
Molar mass 2878.2 g/mol
Melting point 53 °C (127 °F; 326 K)
Flash point Non-flammable
Related compounds
Phosphotungstic acid
Related compounds
Tungsten trioxide
Tungstic acid
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

Silicotungstic acid (also known as tungstosilicic acid) is the most commonly encountered heteropoly acid. It is a pale yellow solid with the chemical formula H4[W12SiO40]. It is used as a catalyst in the chemical industry.[1]


Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene:

C2H4 + CH3CO2H → CH3CO2C2H5

It has also been commercialized for the oxidation of ethylene to acetic acid:[1]

C2H4 + O2 → CH3CO2H

This route is claimed as a "greener" than methanol carbonylation. The heteropoly acid is dispersed on silica gel at 20-30 wt% to maximize catalytic ability.

It has also recently been proposed as a mediator in production of hydrogen through electrolysis of water by a process that would reduce the danger of explosion while allowing efficient hydrogen production at low current densities, conducive to hydrogen production using renewable energy.[2]

Silicotungstic acid Is also used for detecting nicotine and measuring its concentration.

Synthesis and structure

The free acid is produced by combining sodium silicate and tungsten trioxide followed treatment of the mixture with hydrochloric acid.[3] The polyoxo cluster adopts a Keggin structure, with Td point group symmetry.


  1. ^ a b Misono, Makoto (2009). "Recent progress in the practical applications of heteropolyacid and perovskite catalysts: Catalytic technology for the sustainable society". Catalysis Today. 144 (3–4): 285–291. doi:10.1016/j.cattod.2008.10.054.
  2. ^ Rausch, Benjamin; Symes, Mark D.; Chisholm, Greig; Cronin, Leroy (September 12, 2014). "Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting". Science. American Association for the Advancement of Science. 345 (6202): 1326–1330. doi:10.1126/science.1257443. PMID 25214625. Retrieved October 6, 2014.
  3. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.