Abstract: A computer interface technique was applied to the data collecting system of the apparatus for measuring freezing points of mixtures. The sampling of experimental data, the plotting of heating curves and calculating of freezing points and activity coefficients were completed automatically. The apparatus is capable of measuring the freezing point of mixtures with a reproducibility of ±0.001K and the solvent partial molar excess Gibbs free energy with a reproducibility of ±0.1 J mol~(-1).
In this paper, the solvent activity coefficients of binary associated mixtures have been measured for n-propylamine, isopropylamine, n-butylamine, isobutylamine, n-amylamine, isoamylamine, diethylamine, diisoproylamine, triethylamine and tributy-lamine in benzene and p-xylene. The mole fraction concentrations of solute are ranged from 0 to 0.1 and 0 to 0.2 for benzene and p-xylene respectively. The solvent activity coefficients for all systems are greater than unity. A modified three parameter association model, which contained a dimerization constant K_2, a formation to treat the experimental activity coefficients. Under the condition of w=0, this three-parameter model is reduced to the ideall association model. It is shown that the association constants K_2 decrease in the following order:
Primary>secondary amines>>tertiary amines
A similar order...