This project is a continuation of a research program designed to understand and model adsorption of enhanced oil recovery (EOR) chemical flooding material onto reservoir minerals. The understanding and modeling of adsorption will ultimately lead to an effective way to select EOR chemicals which are most cost effective. This report describes progress made from October 1, 1984 to September 30, 1985. It is divided into three parts: (1) modeling of adsorption, (2) adsorption of surfactants from solutions of brine and aqueous cosurfactant, and (3) proving the usefulness of titration calorimetry. In the first part, the surface described was water-wet; in the other parts, surfaces of different wettability were used in the investigations. The adsorption of cosurfactant from hydrocarbon onto silica is modeled by a Langmuir isotherm. This model indicates that the adsorption is driven by enthalpy, taking place with an unfavorable entropy change. It is physical adsorption and does not exceed monolayer coverage. Strong brine seems to have little effect on the adsorption of nonionic surfactant, except in the case of Florisil, a magnesia containing silica. In the presence of cosurfactant, the energy of adsorption is in general higher than that from pure water. All of these enthalpies of adsorption are negative, thus implying lower adsorption as temperature is raised. The titration calorimeter has proved to be a useful instrument for studying adsorption. The measurement of the interaction of nonionic surfactant with silica show satisfactory agreement with the results of the flow calorimeter. Adsorption on kaolin, bentonite, and sandstone can be measured with this instrument, whereas these solids are not amenable to flow calorimetry. 10 figs. 6 tabs.