The molten mixtures of xNa2O-(100 - x)B2O3 and xNa2O-Re2O3-(100 - x) B2O3 (Re = Sm, Eu), where x is a mole % Na2O, were studied by electron spectroscopy. In these mixtures, as the concentration of sodium oxide increases, cyclic changes in the coordination numbers of boron atoms are found. The selected minima on the "concentration of the BO4/2-concentration of sodium oxide" groupings have a different origin. The rupture of the boron-oxygen network of the melt xNa2O-(100 - x)B2O3 occurs at x > 40, and in ternary borate mixtures at x > 30. It is assumed that the coding numbers of samarium and europium ions increase from 6 to 8 in the interval 0 < x <10 and remain constant for x > 10.