Liquid slag properties are essential for understanding complex mass and momentum phenomena in metallurgical operations. The density, surface tension and viscosity were measured in six silicate-rich slags of the CaO–SiO2 and CaO–SiO2-‘Fe2O3’tot systems by combining the maximum bubble pressure and rotating bob methods. The properties investigated were sensitive to the temperature, SiO2 and Fe2O3 contents. Different experimental trends were derived due to the amphoteric properties of Fe2O3. The slags with ferric oxide were denser than the silicate melts. Surface tension gradually decreased with temperature and indicated firstly a rise and then decline with further Fe2O3 addition. Raman spectra were analyzed to provide structural information of the polymer melt and indicated an enhancement in the polymerization degree with Fe3+. The derived experimental trends and role of Fe3+ in the silicates were attributed to the interplay of complex factors: different bonding in the melt, cation interactions and the oxidation state of iron. The influence of Fe3+/Fe2+ on the melt properties was discussed.

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