MOLAR VOLUME AND ELECTRICAL-CONDUCTIVITY MEASUREMENTS IN THE TERNARY MOLTEN-SALT SYSTEM NACL-CSCL-MNCL2 .1. MOLAR VOLUMES

Densities in the ternary system NaC1-CsCl-MnCl2 have been measured by the Archimedian technique at temperatures varying between 550° and 1050°C. The molar volumes of the solutions show positive deviations from additivity which become more pronounced in the CsCl-rich melts. The behavior of the system is explained in terms of a complex ion model based on the presence of NaMn2C14 and Cs~MnC14 complex species in these melts. It is shown theoretically and proven experimentally that the molar volumes in the ternary system may be predicted by the simple expression [formula omitted] where t = XCsCl/(XNaCl + XCsCl), V1,2,3 is the molar volume of the ternary system, and V1,2 and V1,3 are the molar volumes of the binary system MnCl2CsCl and MnCl2-NaCl, respectively, having the same MnCl2 content as the ternary. This expression is valid along a composition path for which y = constant, where y = 1 - -XMncl2 It is of interest to note that the t-fraction average equation formulated herein was also found, applicable to predicting the enthalpy of mixing and activities in several ternary systems (7) from data on their component binary systems. © 1979, The Electrochemical Society, Inc. All rights reserved.