| Abstract
| - The catalytically interesting binary system Rb2S2O7−V2O5 has been investigated by means of calorimetricand conductometric methods. Seventeen different compositions of the binary system in the mole fractionrange XV2O5 = 0−0.45 have been investigated, and the phase transition temperatures obtained. Based onthese, the phase diagram of the Rb2S2O7−V2O5 system has been constructed in the indicated compositionrange. The phase diagram exhibits a local maximum at XV2O5 = 0.33 and probably also at XV2O5 = 0.5. Thiscorresponds to the formation of two compounds Rb4(VO)2O(SO4)4 and RbVO2SO4, respectively, as foundpreviously in the analogous Cs system. Two eutectics were found at XV2O5 = 0.175 and XV2O5 = 0.43, withthe temperatures of fusion of 348 °C and 397 °C, respectively. The conductivities of each of the 15 moltenmixtures investigated have been expressed by polynomials of the form κ = A(X) + B(X)(t − 470) + C(X)(t− 470)2 + D(X)(t − 470)3. The conductivity of the Rb2S2O7−V2O5 system decreases by increasing molefraction XV2O5 in the melt, indicating decreasing ionic character of the melt. A comparison is made with theanalogous Na, K, and Cs systems.
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