Ammonium thioglycolate, also known as perm salt, is the chemical compound with the formula HSCH2CO2NH4. Being the salt of a weak acid and weak base, ammonium thioglycolic acid exists in solution as an equilibrium mixture of the salt itself as well as the free carboxylic acid thioglycolic acid (HSCH2CO2H) and ammonia : HSCH2COO- + NH4+ ? HSCH2COOH + NH3.