Surface tension of pure liquids and binary liquid mixtures

The pendant drop method, combined with efficient temperature control of the measuring cell, allows high precision in surface tension measurements. The surface tensions of heptane, toluene, N,N-dimethylformamide, cyclohexane, N-methyl-2-pyrrolidone, and propanone were measured as a function of temperature using the pendant drop method. The results were compared with literature data. The surface tension and density of toluene + heptane and N,N-dimethylformamide + toluene at atmospheric pressure were measured over a temperature range. Gibbs excess surface concentrations are derived from the experimental surface tensions, and the influence of activity coefficients is discussed.