CaHSO32

Ca(HSO3)2, commonly referred to as calcium bisulfite or calcium hydrogen sulfite, is a salt composed of calcium ions (Ca2+) and two bisulfite ions (HSO3−). Its formula can be seen as Ca(HSO3)2, and in solid form it is typically a white, water-soluble compound.

In aqueous solution, calcium bisulfite dissociates into Ca2+ and HSO3− ions. It is a source of bisulfite in contexts where calcium is preferred or required, such as certain food, beverage, and chemical processing applications. The bisulfite anion acts as a mild reducing agent and as an oxygen scavenger, helping to protect sensitive compounds from oxidation. The compound is stable at ambient temperatures but can decompose upon heating, releasing sulfur dioxide (SO2) and forming calcium sulfite (CaSO3).

Ca(HSO3)2 is commonly prepared by neutralizing sulfurous acid (H2SO3) with a calcium-containing base such as calcium hydroxide or calcium carbonate, or by processing sulfurous solutions with soluble calcium salts. It may also be encountered as a component in sulfite-based preservation systems, where it contributes to the overall sulfite balance in a formulation.

Applications for calcium bisulfite include use as a sulfite source in winemaking and food processing, where controlled reducing conditions help prevent browning and enzymatic browning reactions. It can also serve as a laboratory reagent for sulfite-related reactions and as a replacement for other bisulfite sources when calcium is advantageous.

Safety considerations include the irritant nature of sulfite compounds and potential respiratory or allergenic sensitivities in some individuals. Proper handling, ventilation, and protective equipment are advised when working with calcium bisulfite.