On the kinetics of the autoxidation of fats

The mechanism of fat autoxidation is elucidated from the rate data. All the data treated here and in an earlier publication follow the same basic rate equation, including the time function f(t) empirically derived for heterogeneous oxidation. Metals and glass (the wall of the reaction vessel) are catalysts. Depending on the state of the catalyst, f(t)=t 2 or f(t)=t. When f(t)=t, the kinetics are first‐order as found for monolayer autoxidation, but in bulk phase they are complicated by a transient stage caused by the solubilization of O 2 into the hydroperoxide micelles produced in the exponential (“autocatalytic”) part of the oxidation. Certain additives, such as inhibitors, affect the catalyst and thereby f(t). The kinetics, as determined by O 2 consumption or by analysis of the remaining unreacted substrate, show the first oxidation step. It is unaffected by further chemical changes of the primary oxidation products, e.g. , decomposition of hydroperoxides and trimerization in the autoxidation of 9,11‐octadecadienoic acid methyl ester.