Silicotungstic acid

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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[edit]

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.