The results of theoretical and experimental studies on the acidity of donor-acceptor complexes of boric acid with polyols – glycerin and sorbitol – in oil-displacing compositions are presented. A model of donor-acceptor acid-base equilibria in coordinating polyol solvents has been created, due to which the constants of poly-selectoric acids formation and ionization were determined by pH-meter and electrical conductivity methods. The obtained constant values  were used to calculate the compositions buffer capacity. Due to the using a mixture of poly-selectoric acids in the compositions at various ratios it was possible to regulate the range of the buffer action.