Thioglycolic acid

Thioglycolic acid (TGA) is the organic compound HSCH2CO2H. It contains both a thiol (mercaptan) and a carboxylic acid. It is a clear liquid with a strong unpleasant odor. It is readily oxidized by air to the corresponding disulfide [SCH2CO2H]2.

TGA was developed in the 1940s for use as a chemical depilatory and is still used as such, especially in the calcium thioglycolate salt form. TGA is the precursor to ammonium thioglycolate that is used for permanents. TGA and its derivatives break the disulfide bonds in the cortex of hair. One reforms these broken bond in giving hair a "perm." Alternatively and more commonly, the process leads to depilation as is done commonly in leather processing

TGA is also used in the making of polyvinyl chloride.

TGA, usually as its dianion, forms complexes with metal ions. Such complexes have been used for the detection of iron, molybdenum, silver, and tin.