Metal ion catalysis of autoxidation in a lard gel

The prooxidant effects of transition metal compounds upon lard triglycerides in an aqueous heterogeneous model system were examined. Catalytic activity of a metal salt depended on its identity, the phase in which it is dissolved, the buffering salts and pH of the system. The iron and copper inorganic salts dissolved in the aqueous phase were powerful catalysts. Other transition metal salts had little positive effect on autoxidation at acid and neutral pH values. Manganous chloride had an inhibiting action. Freeze‐drying reversed catalysis patterns, and Mn ++ and Co ++ became the strongest prooxidants. Cobaltous and manganese stearates were the most active of such compounds. Reversals in catalytic activity were due to the formation or disappearance of aquo ions.