Electrodialysis method with ion exchange membrane is effective for the recovery and the removal of poisonous heavy metals contained in industrial waste-water.
In this study, the concentration of 1N zinc chloride solution was conducted by using an electrodialysis cell consisting of multi-compartments, and the results were as follows:
The concentration of zinc chloride showed an increase in line with an increase in current density. At the current density over 2 A·dm^-2, however, this concentration became a constant, and its value was about 4.4N at the flowing rate of zinc chloride solution 440ml·min^-1.
In these cases, the current efficiency for the concentration of zinc chloride was also a constant and was about 88% at the current density over 2A·dm^-2.The specific electric conductivity of cation exchange membrane in zinc chloride solution was about equal to the case of magnesium chloride solution.

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The membrane resistance of cation-exchange membrane was measured in several salt solutions to examine the relationship between the mobility of ion and counter-ion.
The values of the specific electric conductivity in NaCl, NaNO₃ and Na₂SO₄ solutions indicated no difference.
As to the effects of counter-ion in various salt solutions, the membrane resistances of divalent or tri-valent metalic ions were much larger than those of univalent ions of alkaline metals. However, the membrane resistanses of hydrogen ion and ammonium ion were very small. The mobility ratio of each metalic ion to sodium ion was related to the ionic radius, and its value decreased in accordance with the decrease of the ionic radius and with the increase of the ion charge.
It was concluded that the ion potential was available for the mobility of ion in ion-exchange membrane.

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