The Surface Tension and Structure of Silicate Slags

JSGT 1951 V35 T241-T259

An adaptation of the ring method of determining surface tension has been used at high temperatures for measurements on simple silicate slags. The surface tension–composition relationship has been found to be approximately linear in the binary slags CaO–SiO₂, MnO–SiO₂, FeO–SiO₂ and MgO–SiO₂. Silica lowers the surface tension of the basic oxide, but is not particularly surface active. Slags containing cations of high field strength, e.g.Mn²⁺, have positive temperature coefficients of surface tension. This anomalous behaviour is more marked in acid than in basic compositions. An attempt is made to explain this behaviour in terms of the ionic view of liquid slag structures and by analogy with glasses. It is suggested that the acid slags, which contain complex, ring or chain type silicate ions, tend to break down at higher temperatures into simpler ions of more basic type. The extent of the breakdown is determined by the field strength of the cation present. The experimental results can be interpreted satisfactorily on this basis.

T. B. King