sodium thiosulfate (redirected from Hyposulfite of Soda)

sodium thiosulfate, Na₂S₂O₃, colorless crystalline compound that is more familiar as the pentahydrate, Na₂S₂O₃·5H₂O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or "hypo." Sodium thiosulfate is readily soluble in water and is a mild reducing agent. Because it dissolves silver salts, its major use is in photography for developing film. It is also used in chrome-tanning leather and in chemical manufacture. Sodium thiosulfate is produced chiefly from liquid waste products of sodium sulfide or sulfur dye manufacture. It is also produced from sodium carbonate, sulfur dioxide, and sulfur by a process that involves several steps.

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sodium thiosulfate [′sōd·ē·əm ‚thī·ə′səl‚fāt]

(inorganic chemistry)

Na₂S₂O₃·5H₂O White, translucent crystals or powder with a melting point of 48°C; soluble in water and oil of turpentine; used as a fixing agent in photography, for extracting silver from ore, in medicine, and as a sequestrant in food. Also known as sodium hyposulfite; sodium subsulfite.