Thiourea dioxide is also called formamidine-sulfinic acid or aminoiminomethanesulfinic acid and is often abbreviated as TDO or TUD. Thiourea dioxide is a powdered stable compound, which dissolves in water and decomposes gradually to exhibit a reducing action. But, this reaction is slow, and particularly in an acidic to weakly alkaline region. Thiourea dioxide is stable and its reducing action is weak. Usually, thiourea dioxide dissolves in water and produces sulfoxylic acid through formamidine-sulfinic acid. This reaction is promoted by the application of heat or in the presence of an alkali, and a strong reducing action is thereby exhibited. TDO is useful as a reducing agent ; it reduces vat dyes, ketones to alcools and hydrocarbons and conjugated unsaturated acids to the corresponding saturated acids. It is an excellent antioxidant in the stabilization of percholorethylene. It is mainly used in dyeing and paper making industry stead of using sodium hydrosulphite, organic synthesis in synthetic fibre industry, additive of polymerzation, stabilizer for polythene sensitizer of photographical emulsion.