Molten silicate slags with transition metal oxides roles the accelerated oxidation and decarburization of steel. In 1978 to 1990, Sasabe et al. measured the flow rate of oxygen permeating through molten slags and realized the marvelous increase of the flow rate by 10¹⁰ times by the addition of only 0.2 mass% iron oxide to molten silicate slags. The permeability coefficient of oxygen of molten slags as a physical property is calculated from the flow rate of oxygen. The marvelous increase is interpreted as oxygen transfer through slag like a ball thrust, that is caused by the redox reaction of oxygen at both surfaces and the move of all ions in slag under electric field generated by oxygen potential gradient.