AbstractThe reaction of oxygen at atmospheric pressure with dispersed palm‐kernel bag fat has been studied in the range of temperature 50 to 160°c., but principally at 80°c. and with the fat dispersed on glass surfaces, although the reaction with fat‐impregnated jute has also been studied comparatively. The relationships between oxygen consumption, product formation, total pressure change and heat evolution throughout the reaction have been established and the effects of the specific surface of the fat and the pressure of the oxygen on the reaction velocity have been studied. It appears that the oxygen initially attacks the linoleate present more rapidly than the oleate (which is in greater concentration); the linoleate consequently becomes exhausted first and the reaction rate is modified. The heat of initial reaction is about 59 kg.‐cal./mole. Observations on the formation of peroxide and the disappearance of double bonds during the reaction are discussed in the light of the modern views of Hilditch, Farmer and others on the mechanism of oxidation of unsaturat