Chemical elements
    Physical Properties
    Chemical Properties
      Silicon Tetrahydride
      Silicon Tetrafluoride
      Hydrofluosilicic Acid
      Silicon Subfluoride
      Silicon Tetrachloride
      Silicon Tetrabromide
      Silicon Tetra-iodide
      Mixed Halides of Silicon
      Halogen Derivatives of Silico-ethane
      Halogen Derivatives of Silicopropane
      Halogen Derivatives of Silicobutane
      Halogen Derivatives of Silicopentane and Silicohexane
      Silicon Oxychlorides
      Silicon Dioxide
      Silicoformic Anhydride
      Silico-oxalic Acid
      Silicomes-oxalic Acid
      Silicon Disulphide
      Silicon Monosulphide
      Silicon Oxysulphide
      Silicon Thiochloride
      Silicon Thiobromide
      Silicon Chloroitydrosulphide
      Silicon Selenide
      Silicon Tetramide
      Silicon Di-imide
      Silicon Nitrimide
      Siliconitrogen Hydride
      Silicon Nitrides
      Crystalline Silicon Monocarbide
      Silicon Dicarbide
      Silicon Carboxide
      Borides of Silicon
    PDB 1fuq-4ehr

Silicoformic Anhydride, H2Si2O3

Silicoformic Anhydride, H2Si2O3, was obtained in an impure form by Buff and Wohler, and pure by Friedel and Ladenburg, by decomposing silicochloroform with ice-cold water. The formation of the anhydride is probably preceded by that of the free acid, which then loses water, thus:

2HSiCl3+ 6H2O → 2 HSi(OH)3 + 6HCl + 3H2O

Although orthosilicoformic acid is unstable, its ethyl ester is formed by the action of alcohol on silicochloroform, thus:

HSiCl3 + 3C2H5OH = HSi(OC2H5)3 + 3HCl.

For the less reactive chloroform to yield the corresponding ortho-formic ester, sodium ethoxide must be employed thus:

HCCl3 + 3C2H5ONa = HC(OC2H5)3 + 3NaCl.

Formic anhydride, (HCO)2O, corresponding to (HSiO)2O, is unknown, for any attempt to dehydrate formic acid yields carbon monoxide:

2HCOOH → (HSiO)2O + H2O → 2CO + 2H2O.

Silicoformic anhydride is an insoluble white powder, which should be dried in vacuo over sulphuric acid. It may be heated to 300° C. without decomposition, but at a higher temperature it evolves water and silicane, SiH4, and leaves a residue of silica. It inflames when heated to a high temperature in the air, and emits a phosphorescent light; it is stable towards acids, but reacts with alkalis, forming silicates and hydrogen, thus, e.g.:

(HSiO)2O + 4NaOH = 2Na2SiO3 + H2O + 2H2.

Towards various substances in solution it behaves as a reducing agent; thus it reduces permanganic and chromic acids, and separates sulphur from sulphurous acid, and mercury, silver, gold, and platinum from their salts.

These reducing properties are traceable to the hydrogen atom in silicochloroform, which persists in silicoformic anhydride. Like silicic acid, which it somewhat resembles in physical properties, this compound no doubt consists of polymerised molecules, (H2Si2O3)n.

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