Activities and activity coefficients of indium and tin in their amalgams were determined by means of potentiometric measurements in the temperature region 150°–200°C. The equilibrium potential of indium amalgam was far less noble than that of tin amalgam. In the case of tin amalgam, the activity coefficient decreased rapidly with temperature, but the difference between the normal amalgam potential and the standard electrode potential, E* , was kept practically constant. On the other hand, in the case of indium amalgam the activity coefficient was kept nearly constant, but the value of E* increased fairly. The temperature dependence of the activity coefficient was discussed in relation to the type of the amalgamation reaction. Indium amalgam was considered as a simple mixture of indium and mercury and tin amalgam was regarded as a complex such as SnxHgy , which was dissolved in a simple mixture of tin and mercury.

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