In the previous paper1), it has been reported that O, O-dimethyl-O-(3-methyl-4-nitrophenyl) phosphorothioate (commercial name, Sumithion) has not only an extremely low toxicity but also a superior activity towards insects, compared with any other isomers, homologues and analogues. In this paper, the chemical and the biological properties of Sumithion will be reported in detail.

During the course of investigation on organophosphorus insecticides, many organophosphorus compounds having methyl-, methyl-chloro-, methyl-nitro-, methyl-cyano-, methylthiocyano-, methoxy-nitro-, acyloxy-nitro-, and chloro-cyano-phenyl groups were prepared and their biological activities tested. As the results of these studies, two compounds were found as new low toxic organophosphorus insecticides, namely, O,O-dimethyl-O-(3-methyl-4-nitrophenyl) and O,O-dimethyl-O-(4-cyanophenyl) phosphorothioates.