Abstract: Prior work reported that p-carboxymethylmercaptobenzenestibonic acid was more active than tartar emetic against schistosomiasis japonica.Since it is generally believed that pentavalent antimo- ny compounds are reduced to trivalent ones by’a metabolic process,it would appear worth while to reduce this stibonic acid to the corresponding stibinous compounds and to examine their thera- peutic value. p-Carboxymethylmercaptoaniline was diazotized and then reacted with freshly prepared sodium antimonite,giving p-carboxymethylmercaptobenzenestibonic acid.Treatment of the latter compound with stannons chloride in concentrated hydrochloric acid medium caused the cleavage of the carbon- antimony bond,and phenylmercaptoacetic acid was isolated.If the reduction,however,was carried out in acetic acid medium at-3°in the presence of small quantity of hydrochloric acid,p-carboxy- methylmercaptostibinous chloride was afforded.The latter gave the corresponding stibinous iodide and stibinous oxide on treatment with potassium iodide or ammonia respectively. p-Carboxymethylmercaptobenzenestibinous chloride readily reacted with thioglycollic acid in the presence of sodium bicarbonate,forming a dimercaptide,bis-carboxymethylmercapto-(p-carboxymethyl- mercaptophenyl)-stibine.On heating of the latter compound in aqueous acetone one mole of thio- glycollic acid was readily eliminated,and a chelating salt p-carboxymethylmercaptobenzenestibinous thioglycollate was formed.Condensation of p-carboxymethylmercaptobenzenestibinous chloride with dimercaptopropionic acid gave 1-p-carboxymethylmercaptophenyl-3-carboxyl-2,5-dithia-1-stibia-cyclo- pentane.