Dissolution of Iron and Tin from Tinplate in the Safflower Oil Containing Water and Oxidative Deterioration of the Oil

Abstract

A tinplate was submerged in the safflower oil containing water (201520ppm) with stirring under oxygen, air or nitrogen atmosphere, and the amount of dissolved metals from the tinplate was determined and the autoxidation of the oil was investigated. The amount of tin dissolved was measured by means of neutron activation analysis. The amount of the metal dissolved in the oil increased in proportion to the amount of the water at 20 and 50°C. Under the same temperature and the water content, the amount of metals dissolved was the greatest under nitrogen and decreased under air, and under oxygen.The autoxidation rate of the oil was influenced by the equivalent number of hydroperoxy or peroxy groups [Eq (HPO or PO)] and the number of moles of the dissolved water [M (H2O)]. That is to say, in such case that Eq (HPO or PO) was more than M (H2O), the autoxidation rate was increased by catalysis of the dissolved metal ions. On the condition that Eq (HPO or PO) was nearly equal to M (H2O), the autoxidation rate decreased owing to the formation of the hydrogen bonds among them. In the case that M (H2O) was in excess, the autoxidation rate became smallest on account of the hydrogen bonds and the formation of the hydrates of the dissolved metals.