The precipitated indium hydroxide is converted into a basic sulphite by boiling with excess of sodium bisulphite, and then into the normal sulphite by dissolving in hot sulphurous acid.
A simpler explanation is that the manganese dioxide first gives a normal sulphite which rearranges to dithionate, thus: Mn0 2 +2S0 2 = Mn(S03)2-MnS206, whilst the lead dioxide gives a basic sulphite which rearranges to sulphate, thus: PbO-l-S0 2 = PbOS03 - > PbS04.
Divers obtains it by mixing cold saturated solutions containing one molecular proportion of sodium nitrate, and two molecular proportions of acid sodium sulphite, and then adding a saturated solution of potassium chloride to the mixture.
Ferrous sulphite, FeS03.
Iron dissolves in a solution of sulphur dioxide in the absence of air to form ferrous sulphite and thiosulphate; the former, being less soluble than the latter, separates out as colourless or greenish crystals on standing.