In view of the importance of p, p'-DDT as an insecticidal agent, it was of interest to study some of the reactions of the o, p'-DDT isomer. o $'-DDT, when pure, is a reasonably stable compound. It does not eliminate hydrogen chloride upon heating at 115-120 for two hours. Decomposition of o, p'-DDT, like that of p, p '-DDT, 3 is catalyzed by traces of anhydrous ferric chloride; 1 mole of hydrogen chloride is eliminated and the olefin I1 results.* One ...