Commercial tricresyl phosphale-32 (TCP-32) has been used to illustrate the involvement of P³² in physical adsorption and chemical reaction at the bearing surface. Chromatographic analyses of three commercial batches of TCP-32 indicate the presence of appreciable quantities of polar P³² impurities. Thin-layer and iron-powder chromatography have been studied as analytical tools for the quantitative measurement and separation of TCP-32 and its P³² impurities. The effect of the polar P³² impurities on physical adsorption on the bearing surface is illustrated as a function of polar P³² impurity concentration. The effect of a variety of surface-active additives on P³² adsorption at the bearing surface has also been studied. The wear properties of TCP, acid phosphates, and acid phosphites in several base stocks have been studied to illustrate the effects of polar impurities on the antiwear properties of TCP. The presence of P³² chemically combined with the bearing metal is suggested by the wear studies with TCP-32. A definite relationship is shown between effective antiwear behavior and a high level of P³² chemically combined with the worn bearing surface.