Another route to  is the Raschig process: aqueous ammonium nitrite is reduced by Bisulfite| and Sulfur dioxide| at 0 °C to yield a hydroxylamido-N,N-disulfonate anion:
This anion is then hydrolyzed to give hydroxylammonium sulfate :
Solid  can be collected by treatment with liquid ammonia. Ammonium sulfate, , a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product.
The net reaction is:
A base then frees the hydroxylamine from the salt: