P 1565 (OTTO) Phenothiazine, 98% Cas 92-84-2 - used as the polymerization inhibitor for acrylic acid, acrylic esters, and methacrylic aicd as well as ester monomer. P 1565 (OTTO) Phenothiazine, 98% Cas 92-84-2 - used widely as an intermediate in pharmaceutical manufacture; polymerization inhibitor, antioxidant.