Application of high‐speed centrifugation to studies of plastic spreads

Summary By means of the analytical ultracentrifuge the rate of separation of a plastic spread into liquid and solids phases was observed and the proportions of each phase determined. An estimate of the amount of true solids was complicated by the fact that the solids phase consisted of approximately one‐half oil. In the preparative ultracentrifuge sufficient quantities of the oil phase were isolated for chemical analysis. Centrifugation at each of several temperatures and analysis of the oil and solids phases would yield a characterization of the different components which crystallize at various temperatures. By centrifuging the plastic spread with a layer of aqueous alcohol of density intermediate to the oil and solids, the solids phase was separated more nearly oil‐free. The solids phase however still was not sufficiently pure to permit a chemical characterization representative of the solid component. Corrections can be made however for the effect of occluded oil.