What is "rongalite"

Rongalite, also called Rongalit (registered trademark of BASF), is sodium hydroxymethyl sulfinate, or NaHOCHSO. The salt has many names, including also sodium formaldehyde sulfoxylate, and Bruggolite. It is listed in the European Cosmetics Directive as sodium oxymethylene sulfoxylate ( INCI). It is water-soluble and generally sold as the dihydrate. The compound and its derivatives are widely used in the dye industry.