HYDROSULPHITE OF SODA, a chemical compound of considerable use in the bleaching industry, a special brand being marketed under the name "Hydros." Its chemical formula is and its correct name in systematic chemistry is sodium hyposulphite, but this term is also used for the quite distinct sodium thiosulphate (see HYPOSULPHITE OF SODA). "Hydros" and "Rongalite" are described in the article SULPHUR.