EXPERIMENTAL INVESTIGATION OF THERMODYNAMIC MELTING PROPERTIES IN THESYSTEM NACL-KCL AT PRESSURES OF UP TO 7000 BAR

Thermodynamic melting properties in the system NaCl-KCl, including sol idus temperatures at 1 bar, liquidus temperatures at pressures up to 7 000 bar, heats of fusion (Delta H-f) at 1 bar and volumes of fusion (D elta V-f) from 400 to 2500 bar, have been studied. A new PVT apparatus is presented for measuring Delta V-f at high pressures. The consisten cy of the data is clearly demonstrated by calculating Delta V-f via th e Clausius-Clapeyron equation. Modelling the liquidus temperatures up to pressures of 7000 bar using the thermodynamic approach of WALDBAUM (1969) yields the following Margules parameters of volume [cm(3)/mol]: W-VIL = -0.71, W-V2L = -0.79, W-VIS = -0.36, W-V2S = -0.4. The heat o f fusion data at 1 bar have also been modelled using a cubic Margules term for the excess function with Delta W-H1 = -26,273 J/mol and Delta W-H2 = -16,584J/mol.