Molten salt reactors (MSRs) have received growing interest due to a desire for high temperature reactors that are not constrained by the limitations of solid fuels and conventional coolants. The proposed salt systems found in the literature vary widely and basic properties are missing. In particular, thermophysical properties that are critical for design of an efficient and reliable heat exchange fluid are not well documented or understood. This study has focused on the simple binary compositions, LiF-NaF and KCl-NaCl, as a baseline to understand the effects of composition on thermal conductivity, heat capacity, melting temperature, and high temperature stability. For instance, at 600 °C, the heat capacity of the eutectic F composition, 2.09 J/g·K, is roughly three times higher than the equivalent Cl composition, 0.57 J/g·K. This talk will detail the synthesis process, characterization techniques, and the effects of composition on the thermal properties of the binary molten salt systems.