Description
Sulfuric(IV) acid (United Kingdom spelling: sulphuric(IV) acid ), also known as sulfurous (UK: sulphurous ) acid and thionic acid , is the chemical compound with the formula H2SO3.
Raman spectra of solutions of sulfur dioxide in water show only signals due to the SO2 molecule and the bisulfite ion, HSO−3. The intensities of the signals are consistent with the following equilibrium:
17O NMR spectroscopy provided evidence that solutions of sulfurous acid and protonated sulfites contain a mixture of isomers, which is in equilibrium:
Attempts to concentrate the solutions of sulfurous acid simply reverses the equilibrium, producing sulfur dioxide and water vapor. A clathrate with the formula 4SO2·23H2O has been crystallised. It decomposes above 7 °C.
