Ammonium Bisulfite, also known as ammonium hydrogen sulfate, is a white, crystalline solid when it is completely pure, with formula (NH4)HSO4. Pure ammonium bisulfite is a white crystalline solid. Commercially, aqueous liquid form is common. Ammonium bisulfite’s reductive and sulfonating properties provide versatile applications. It is used as an oxygen scavenger to eliminate the dissolved oxygen in waste water and in pipes.

Ammonium bisulfite is a reductive bleaching agent. It reduces carbonyl and alcohol groups, which function as colorants of the substances. It is used in bleaching mechanical paper pulp, cotton, wool and kaolin clay.

Additional applications include as a preservative (antioxidant) and a hair waving agent. Ammonium bisulfite is used in industries concerned with leather processing, food and beverage processing, gas purification, water treatment to remove excess chlorine, textiles and pulp processing, and many others. It is used as a reducing agent in chemical manufacturing. It is an alternative to sulfur dioxide which is used in sterlization of equipment.