Determination of NiO and PbO solubilities in molten BaBr2-KBr (0.505:0.495) eutectic at 973 K (of pK(s,Nio) = 8.06 +/- 0.2 and pK(s,Pbo) = 4.04 +/- 0.2, molality scale) allowed completing systematic oxide solubility studies in molten ionic bromides. On the basis of the obtained and literature data the acidity scale for chloride and bromide melts (KX-NaX --> BaX2-KX --> KX-LiX sequences, X= Cl, Br) at 973 K was built on the basis of primary medium effects (estimated as oxobasicity indices). The oxoacidic properties of chloride and bromide melts with similar cation composition are close, although the acidity of bromide analogs is always somewhat weaker. The obtained information permits to predict e.g., limits of halide melt purification by precipitating deoxidization or carbohalogenation methods. (C) 2015 Elsevier B.V. All rights reserved.