Rongalite

the commercial name for the sodium salt of for-maldehydesulfoxylic acid, which is unknown in the free state. Rongalite’s formula is HOCH₂S(O)ONa.2H₂O. Rongalite forms colorless, hygroscopic crystals, is freely soluble in water, and has a melting point of 63°–64°C. It loses its water of crystallization when heated to 120°C and decomposes at higher temperatures. Rongalite is obtained by, among other methods, reduction of the bisulfite derivative of formaldehyde with zinc dust. Because of its strong reducing properties, it is used in bleaching, for example, textiles, sugar, and fats. It is also used to introduce the—CH₂SO₂Na group into organic compounds, for example, in the synthesis of neoarsphenamine, to increase the solubility of these compounds in water.