Since a variety of systems have been investigated, a study was done to investigate the individual adsorption of a mixed solution. This phenomenon is also called competitive adsorption because solutes tend to compete for the same adsorption sites. In the experiment conducted by Rosene and Manes, the competitive adsorption of glucose, urea, benzoic acid, phthalide, and p-nitrophenol. Using the Polanyi adsorption model, they were able to calculate the relative adsorption of each compound onto the surface of activated carbon.