Sodium thioglycolate is a white powder with a melting point greater than 300 degrees Celsius. It appears as hygroscopic crystals with an unpleasant odor characteristic of the sulfhydryl group (mercaptans). Thioglycolic acid can be prepared by the action of sodium sulfhydrate on sodium chloroacetate and by electrolysis of dithioglycolic acid from sodium sulfide and sodium chloroacetate. It is also formed by heating chloroacetic acid with potassium hydrogen sulfide. Thioglycolic acid and its salts and glyceryl esters are not known to occur naturally. Sodium thioglycolate is used in the cosmetic industry as an antioxidant, depilating agent, hair waving/straightening agent, and reducing agent. Its primary cosmetic use is in depilatories. Sodium thioglycolate is also used as an analytical reagent and in bacteriology for the preparation of thioglycolate media. Sodium thioglycolate was nominated by the National Cancer Institute for toxicology studies due to its high production volume and widespread occupational and consumer exposure to thioglycolic acid and its salts and esters, including significant female exposure in personal care products. Male and female F344/N rats and B6C3F1/N mice were administered sodium thioglycolate (approximately 99% pure) in a vehicle of 95% ethanol:deionized water (1:1) by application to shaved dorsal skin for 16 (rats) or 17 (mice) days or for 3 months. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. (Abstract Abridged).
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