thioglycolic acid
noun
thio·gly·col·ic acid
variants:
also thioglycollic acid \ -glī-ˌkäl-ik- 
\
\
Medical Definition of thioglycolic acid
: an ill-smelling liquid mercapto acid C2H4O2S that is used as a reagent for ferric iron and especially in the form of its calcium salt as a depilatory