Steel quality depends on various factors, i.a. on the slag basicity and oxidation potential. These values can be determined by means of emf measurement using solid electrolyte based sensors. Liquid iron can serve as a cation electrode. Activity of ferrous oxide and manganese oxide can be found out. Ferrous oxide activity determines the oxidation potential and manganese oxide activity can be used for the basicity estimation. Sulphide and phosphate capacity can be calculated and distribution coefficients of oxygen, sulphur, manganese, and other elements can be predicted....