The effect of oxidation state on the viscosity of melts in the system Na2O-FeO-Fe2O3-SiO2

The viscosities of two melts in the system Na2O-FeO-Fe2O3-SiO2 have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts. 57Fe Mössbauer spectra were obtained on quenched melt samples recovered during the viscometry experiments. In addition, a series of loop fusion experiments were performed at calibrated ƒO2 values in order to relate viscosity determinations directly to ƒO2. The viscosities of acmite and NS4F40 (Na-rich and Si-poor relative to acmite) melts decrease with reduction of Fe in the melts, as nonlinear functions of , yielding a region of viscosity invariance at moderate to low values of (