Hydroxylammonium sulfate is the inorganic compound with the formula [NH<sub>3</sub>OH]<sub>2</sub>SO<sub>4</sub>. A colorless solid, it is the sulfate salt of hydroxylamine. It is primarily used as an easily handled form of hydroxylamine, which is a volatile liquid.
Hydroxylammonium sulfate is prepared industrially by protonation of hydroxylamine. The latter is produced by the hydrogenation of nitric oxide using a platinum catalyst:
Another route to is the Raschig process: aqueous ammonium nitrite is reduced by and at 0 ðC to yield a hydroxylamido-N,N-disulfonate anion:
This ammonium hydroxylamine disulfonate anion is then hydrolyzed to give hydroxylammonium sulfate:
Almost all hydroxylamine and its salts are used to make precursors to nylons via cyclohexanone oxime. Many aldehydes and ketones undergo the same conversion to oximes. carboxylic acids and their derivatives (e.g. esters) convert to hydroxamic acids. Isocyanates to N-hydroxyureas. Nitriles react to give amidoximes. Hydroxylammonium sulfate is also used to generate hydroxylamine-O-sulfonic acid from oleum or from chlorosulfuric acid.
Hydroxylammonium sulfate is used in the production of anti-skinning agents, pharmaceuticals, rubber, textiles, plastics and detergents. It is a radical scavenger that terminates radical polymerization reactions and serves as an antioxidant in natural rubber. (NH<sub>3</sub>OH)<sub>2</sub>SO<sub>4</sub> is a starting material for some insecticides, herbicides and growth regulators. It is used in photography as a stabiliser for colour developers and as an additive in photographic emulsions in colour film.
Hydroxylammonium sulfate exists as tetrahedral cations and sulfate anions.
Hydroxylamine, which occurs widely in nature, has low toxicity. The compound is stable below 120 ðC.