The distribution ratios of copper (II) ion between an aqueous solution containing mixtures of Cu (NO3)(2)-HNO3-KNO3 at various pH and the organic phase containing bathocuproine (L) in 1, 2-dichloroethane were KNO3 measured. From the variation in the absorption spectra, it was found that the ligand is distributed between both phases by forming HL(+) in the aqueous phase and HLX in the organic phase, respectively, in the range of pH from about 1 to 5.5. The extractability of copper (II)-complex, CuL(2) (NO3)(2), decreases rapidly with the decrease in pH value of the aqueous solution. As a result, it became clear that the effect of hydrogen ion on the distribution ratio can be utilized for the concentration and separation of copper (II) ion through a liquid membrane between both aqueous phases of Cu (NO3)(2) at different pH.