Density and surface tension of slag melts of the system Fe2O3−FeO-CaO−SiO2

The effect of SiO 2 on the density and surface tension of Fe 2 O 3 -FeO-CaO-SiO 2 slag melts was studied at concentrations of up to 10 wt.% SiO 2 The maximum gas bubble pressure method was employed in the measurements. Silica reduces density and surface tension, while increasing the molar volume and statistically mean size of ions present in the ferritic-lime melt. The results showed that the physical properties of slag systems are for the most part influenced by the character of anionic ferric oxide complex compounds. The Fe 3+ cation can form FeO + , FeO 2 + , Fe 2 O 5 4- and FeO 4 5- complex compounds with oxygen while possibly also changing oxygen coordination of the iron ions. At the concentrations in question, SiO 2 occurs mostly in the form of SiO 4 4- tetrahedrons.