The surface tension and the density of molten Li2CO3-X2CO3 (X : Na, K, Rb,
and Cs) and Na2CO3- Y2CO3 (Y: K, Rbl and Cs) binary carbonate systems were
measured using maximum bubble pressure technique. The addition of Rb2CO3 or
Cs2CO3 to Li2CO3 or Na2CO3 effectively decreases the surface tension of mi
xtures. At constant temperature, the relationship between surface tension a
nd composition in all binary carbonate systems was well correlated by the G
uggenheim's Equation for regular solution. The molar volume of Li2CO3-Rb2CO
3 and Li2CO3-Cs2CO3 systems shows positive deviation from additivity.