Hydroxylamine-disulphonic Acid, N(OH)(SO₃H)₂

Hydroxylamine-disulphonic Acid, N(OH)(SO₃H)₂ may be prepared by the addition of the alkali hydrogen sulphite in concentrated aqueous solution to the alkali nitrite. They are also formed when excess of sulphur dioxide is passed through a solution containing the alkali nitrite and either the alkali carbonate or hydroxide. The presence of caustic alkali confers stability on the compound, whilst acids decompose it even in the cold, hydroxyl-amine monosulphonic acid being formed.