Adsorption excesses of binary liquid mixtures are the primary experimental quantity in liquid-phase adsorption onto porous or disperse solids.Binary liquid adsorption isotherms can here be easily measured and allow statements to be made about the characteristics of solid and liquid mixtures, immersion behaviour at the liquid/solid interface, multi-component adsorption, etc.In this paper, a brief summary is given of different ways of interpreting and analysing binary isotherms over the read more whole concentration range.Experimental data and calculation examples show that thermodynamics provides a powerful tool for obtaining relevant information from such isotherms.