Thermodynamic properties of binary alkali borate systems Me2O-B2O3 have been studied in the framework of sub-regular solution theory approximation. The oscillation method of phase analysis was used to obtain precise data for solid-liquid equilibria. A nonmonotonic correlation function for these properties (the melting temperature and entropy of melting, the exchange energy for infinitely dilute solution of a metal oxide in the melt of boron oxide) and the alkali ionic radii of borate compounds nMe(2)O center dot mB(2)O(3) is suggested. It is found as a first approximation that a melt supercooling grows when a compound dissociation degree rises. (C) 2007 Elsevier B.V. All rights reserved.