Sodium Hydrosulphite

Sodium dithionite (also known as sodium hydrosulfite) is a white crystalline powder with a sulfurous odor. Although it is stable in dry air, it decomposes in hot water and in acid solutions.

The structure has been examined by Raman spectroscopy and single-crystal X-ray diffraction. The dithionite dianion has C
2 symmetry, with almost eclipsed with a 16° O-S-S-O torsional angle. In the dihydrated form (Na
2S
2O
4·2H
2O), the dithionite anion has gauche 56° O-S-S-O torsional angle.^[1]

A weak S-S bond is indicated by the S-S distance of 239 pm, which is elongated by ca. 30 pm relative to a typical S-S bond.^[2] Because this bond is fragile, the dithionite anion dissociates in solution into the [SO₂]⁻ radicals, as has been confirmed by EPR spectroscopy. It is also observed that ³⁵S undergoes rapid exchange between S₂O₄²⁻ and SO₂ in neutral or acidic solution, consistent with the weak S-S bond in the anion.^[3]

• Packaging Details: 200 KG * 1 DRUMS