Summary A procedure is reported leading to the isolation of o, o'-DDT from technical DDT in amounts of about 0.1% of the original product. The method involved isolation of the DDT- isomer fractions by crystallization and chromatographic analysis and preferential dehydrochlorination of the more reactive DDT isomers, followed by oxidation of these products, leaving the unreactive o, o'-DDT. The structure of o, o'-DDT has been proved by ...