MEASUREMENTS OF THE MOLAR VOLUMES OF LIQUID CS-AU ALLOYS

This study reports on a method for density measurements, which has been used to measure the densities of liquid Cs-Au alloys up to 800 degree C. Strong deviations from ideal mixing behavior have been observed in this system; the excess volume is negative and reaches at 650 degree C its maximum value of minus 22. 1 cm**3/mol near to the stoichiometric composition CsAu, where the mean molar volume is 27. 8 cm**3/mol. The partial molar volumes of Cs and Au are evaluated from the concentration dependence of the mean molar volume of the mixtures, giving values as large as minus 100 cm**3/mol for the partial molar volume of Au at low gold concentrations. The concentration dependence of the partial molar volumes is discussed in connection with the transition from metallic to ionic electrical transport in these alloys.