Solid and liquid iron oxides exhibit characteristics ofsemiconductors. The semiconductive behavior also featuresin some slags containing iron oxide. This paper aims athighlighting some of the experimental indications of the roleof semiconductivity in electrical conduction, the chemicaldiffusion and in reaction kinetics at slag surfaces. It is nota thorough review of the subject matter but an attemptat shedding some light on the connection between theseproperties.