MEASUREMENT OF BOILING TEMPERATURES AND CALCULATION OF VAPOR PRESSURE AND THERMODYNAMIC PARAMETERS OF LEAD AND ZINC CHLORIDE MELTS

摘要

The pressure of saturated vapor over melted mixtures of PbCl_2-ZnCl_2 in the interval of temperatures T = 850 - 1150 K is experimentally measured over the entire range of compositions. The data are represented by the equation log P = - (A +- DELTA A)/T + (B +- DELTA B), where the constants are computed by the method of least squares. The enthalpies of evaporation and the normal boiling temperatures are calculated. The total pressure in the system is determined in light of published data on the activities of the components. The computed data thus obtained are compared with experimental data and it is shown that they coincide for certain compositions and temperatures; reasons for differences between these data are explained. The activities of the components are calculated from the experimental data for T = 1000 K. An analysis of the fusion diagram is performed in light of the available test data and the results of calculations on the basis of a study of deviations from Raoult's law. The results demonstrate that the fusion diagram of the system PbCl_2-ZnCl_2 is of the eutectic type and that the most probable coordinates of the eutectic point are T = 260 deg C and x_(PbCl_2) = 0.2.