Water transference through nickel hydroxide precipitate membrane

The transference of water that results from ion migration through the nickel hydroxide precipitate membrane was studied in chloride, perchlorate, nitrate, and sulphate solutions to estimate the transference number of water and the co-ion transport. In the systems of univalent anions, the moles of water transported per mole of electrons in 0.1 N solutions is almost identical to the hydration number of each anion. This water flow decreases gradually as the concentration of external solution increases, because of increase in the co-ion (cation) transport with increasing concentration of the solution. In the system of sulphate solutions the co-ion transport is remarkable, the transport number of Na⁺ ions being 0.03 in 0.01 N, 0.27 in 0.10 N, and 0.50 in 0.5 N Na₂SO₄ solution. This large co-ion transport in Na₂SO₄ solution is attributed to the partical replacement of hydroxyl groups on the membrane by SO^2?₄ ions, which then acts as a negative fixed charge. The order of the selectivity for co-ion transport is K⁺ > Na⁺ > Li⁺ > Ni²⁺ ? Mg²⁺ in sulphate solutions and also in chloride solutions, although the transport number of the cations is much smaller in chloride solution than in sulphate solution.