Figure 13 shows the composition dependence of the (a) mass density, (b) glass transition temperature, and (c) dissolution rate (DR) found in the work of Mosner et al. for the (Nb2O5)_x(Na2O)_{0.4}(P2O5)_{0.6-x} glass series.  In (b) and (c), the curves show the results from model I for kappa = 2.75.