Sulphite

It has chemical formula (NH4)2SO3.

Causes severe irritation and burns. May Be harmful if swallowed. Avoid breathing vapor or dust. Use with adequate ventilation. Avoid contact with eyes, skin, and clothes. Wash thoroughly after handling. Keep container closed.

It is white Solid powder having SO2 odor.

It is White to yellow white crystalline granules.having Slight odor of sulfur dioxide.

Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na2S2O5. The name is sometimes referred to as disodium (metabisulfite, etc). It is used as a disinfectant, antioxidant and preservative agent.