The sequential additions method (SAM) was used to determine solubility and disassociation characteristics of metal oxides MeO (CaO, PbO, ZnO, CdO) and carbonates (CaCO3, SrCO3, BaCO3) in molten KCl-NaCl eutectic at 700 degreesC. A membrane oxide-reversible electrode Pt(O-2)/YSZ) was used to detect oxide ion concentrations. The oxides (MeO) were found to be weak bases in unsaturated solutions, their dissociation constants (pK) were found to be 3.27 +/- 0.2 (CaO), 3.50 +/- 0.1 (PbO), 6.1 +/- 0.2 (ZnO) 5.3 +/- 0.2 (CdO). All the emf-(-log m(MeO)) plots in the vicinity of the saturation point include bends to the concentration axis. These were explained by the partial dissolution of MeO powders resulting in a decrease of their particle sizes and a corresponding rise of the molar surface areas (MSA). Calculations performed give surface energies of MeOsolid/KCl-NaCI systems of the order of 30-50 J m(-2). This allowed us to estimate MSAs of the MeO particles formed in MeO solubility determinations in molten KCl-NaCl by isothermal saturation and potentiometric titration methods. The solubilities of the alkaline earth carbonates were determined in a CO2 atmosphere. Under these conditions solubility products of the carbonates were achieved before oxide precipitation. The alkaline earth carbonates were found to be appreciably soluble in the KCl-NaCl eutectic at 700 C. Their solubility products determined by SAM were equal to pP(BrCO3) =0.36+/-0.3, pP(SrCO3) =2.04+/-0.2, pP(CaCO3) =2.04+/-0.2 (in a CO2 atmosphere). Under these conditions the particle size effect was imperceptible.