What is the Difference Between Sodium Bisulfite and Sodium Metabisulfite?

Sodium bisulfite and sodium metabisulfite are two different chemical compounds, but they are closely related and have similar uses. The key differences between them are:

1. Chemical Formula: Sodium bisulfite has the chemical formula NaHSO3, while sodium metabisulfite has the chemical formula Na2S2O5.
2. Valency: Sodium bisulfite and its bisulfite anion are monovalent, whereas sodium metabisulfite has two sulfur atoms, five oxygens, and its anion is divalent.
3. Solubility: When sodium metabisulfite is dissolved in water, it forms sodium bisulfite.

Both sodium bisulfite and sodium metabisulfite are primarily used as preservatives, disinfectants, and food additives. They are both available in powder form and have the foodstuff additive numbers E222 and E223, respectively. In practice, the two compounds can sometimes be used interchangeably, as sodium metabisulfite dissolves into sodium bisulfite when mixed with water. However, it is essential to consider the specific application and desired properties before choosing between the two compounds.

Comparative Table: Sodium Bisulfite vs Sodium Metabisulfite

The key difference between sodium bisulfite and sodium metabisulfite is that sodium bisulfite has only one sulfur atom and three oxygen atoms, whereas sodium metabisulfite has two sulfur atoms and five oxygen atoms. Sodium bisulfite is represented by the chemical formula NaHSO3 and has a molar mass of 104 g/mol. On the other hand, sodium metabisulfite is represented by the chemical formula Na2S2O5 and has a molar mass of 158 g/mol.