Abstract: Antimonial catechol, which is insoluble in water,is a well-known therapeutic agent. Various efforts were made to solubilize this compound.It was reported in literature that this antimonial derivative combined with amines and hydroxy compounds such as alcohols, glycols, glycerol or carbohydrates to form the chelating compounds Ⅱ,whilst Ⅲ was formed on combination with hydroxyamines. Similar compounds were also recorded on the treatment of I with o-,m- and p-hydroxybenzoic acids,as well as with tartaric acid in the presence of sodium bicarbonate.In the latter case Ⅳ was suggested as the structure of the reaction product.The designation of these structures were only based on the data of antimonial analyses or sometimes on a ratio of antimony and nitrogen. The reaction of I with tartaric acid and sodium bicarbonate was repeated in the present work. Identical product was obtained by the action of sodium bicarbonate on catechol whether in the presence or in the absence of tartaric acid.This finding is inconsistent with the structure Ⅳ.The same compound was also formed on treatment of catechol with antimonous acid and sodium carbonate,and,from the analytical data,it was assigned the antimonial dicatechol structure(Va).The corresponding potassium salt(Vb)was similarly prepared. The o-,m- and p-hydroxybenzoic acids gave identical product on treatment with antimonial catechol and sodium bicarbonate.The product was also identical with Va. Antimonial catechol was treated with ammonia and various hydroxy compounds such as methanol,glycerol etc.The reaction product was found not to be Ⅱ(R'=H),but rather the ammonium salt of antimonial dicatechol(Vc).The product was not altered even in the absence of the hydroxy compounds.Similar results were observed when various amines were used in the place of ammonia.Identical products were formed when catechol reacted with antimonous acid and the corresponding amines.If hydroxyamines were employed,the hydroxyammonium salts instead of Ⅲ were formed respectively. Several salts of antimonial dicatechol, formed in the present work,were tested on mice infected with schistosomiasis japonica, and they were as active as tartar emetic.