Measurement and calculation of the phase diagram of the NaClCaCl 2SrCl 2 system

Abstract

In this paper the system NaClCaCl 2SrCl 2 and its binary systems were studied. Using a previously calculated phase diagram of the NaClCaCl 2SrCl 2 system as a basis, accurate measurements were carried out by MDTA with high sensitivity. It is a simple eutectic system with a eutectic point at 41.9 mol % NaCl, 40.C mol % CaCl 2, 18.1 mol % SrCl 2, 744 K. In the liquidus surface for saturation with the CaCl 2SrCl 2 solid solution a univariant line starts from a point 24.8 mol % NaCl, 50.1 % CaCl 2, 25.1 mol % SrCl 2 at 823 K. The uncertainty in the liquidus temperatures is estimates to be less than ±5K, for the reason that the errors due to Supercooling and change of sample compositions were reduced by our experimental method. A new calculation of the phase diagram of the NaClCaCl 2SrCl 2 system has been performed with a new asymmetric method. It is based upon a critical assessment of the thermodynamic properties and phase diagrams of the binary systems. The agreement between our present measured and calculated phase diagrams is within ±2.5 mol %. Their good agreement indicates that the phase diagram calculated from the binary data is relatively sensitive to the se1f-consistency between thermodynamic properties and phase diagrams of binary systems.