Ammonium bisulfate, also known as ammonium hydrogen sulfate, is a white, crystalline solid with the formula (NH4)HSO4. This salt is the product of the half-neutralization of sulfuric acid by ammonia.
Production It is commonly collected as a byproduct of the "acetone cyanohydrin route" to the commodity chemical methyl methacrylate.William Bauer, Jr. "Methacrylic Acid and Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. .
It can also be obtained by hydrolysis of sulfamic acid in aqueous solution, which produces the salt in high purity:
It also arises by the thermal decomposition of ammonium sulfate:
Applications It can be further neutralized with ammonia to form ammonium sulfate, a valuable fertilizer. It can be used as a weaker alternative to sulfuric acid, although sodium bisulfate is much more common.
Natural occurrence A related compound of the (NH4)3H(SO4)2 formula, occurs as the rare mineral letovicite, known from coal fire environments.
References