IONIC COMPOSITION OF POLYTUNGSTATE MELTS

The ionic composition of a melt is defined as the minimal number of di fferent kinds of ion sets that allows one to describe the thermodynami cs of the melt within the given composition range to a given accuracy and under the assumption that the activity coefficients of these ionic forms do not depend on their concentration in the melt. The ionic com position of the (1 - x)Na2WO4-xWO3 melt is calculated on the basis of experimental data on the equilibrium potentials of the tungsten electr ode. The ionic composition is calculated in the concentration range of x = 0.01 to x = 0.45 and in the temperature range of 1 100 to 1373 K. It is shown that the experimental data may be described to an accurac y of +/-0.01 V when we assume that Na+, O2-,WO42-, W2O72-, W3O102- are contained in the melt.