For the both purposes of improving the efficiency and preventing the deposition of scales, the ion exchange membrane used for sea water concentration undergoes in most cases a treatment which gives it permselectivity among counter-ions (the permselectivity treatment).
However, it has less effectiveness in decreasing the permeability of total carbonates (CO₂+HCO₃^-+CO₃^-) through anion exchange membranes treated under general conditions of sea water concentration. In the process of the permselectivity treatment, the permeability of sulfate ion showed a gradual decline, but the permeability of the total carbonates was kept almost unchanged. This was due to the fact that most of the total carbonates migrated through the membrane as univalent hydrogen carbonate ion under the general conditions. At higher pH, on the other hand, divalent carbonate ion became dominant form, promoting the effect of the permselectivity treatment prominently. Therefore, the effect of the permselectivity treatment was considered to depend upon the valencies of migrating ions. At pH<2, the permeability of total sulfates (HSO₄^-+SO₄^-) showed a rise because appreciable part of sulfate became hydrogen sulfate form.
Therefore, much attention is paid when acidified sea water is concentrated.

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The author made a study on relations between the deposition conditions of calcium carbonate and its crystal modifications thereunder. In this study, carbonate ion was introduced electrodialytically into the concentrating compartment and reacted with calcium ionin the solution of the compartment. The rate of deposition was as large as about 0.6-10g/liter·hr Al (OH) ₃ was used as an intemal standard of the X-ray diffraction analysis of the crystal modification.
Results obtained were as follows:
1. The Al (OH)₃ used as the internal standard for the quantitative analysis of calcite, a ragonite and vaterite proved to be satisfactory.
2. At4-10g/liter·hr in the rate of deposition, calcite was formed even in concentrated sea water or other solutions containing Mg⁺⁺. The ratio of calcite in CaCO₃ showed an increase at higher temperature and larger rate of deposition, and with smaller content of Mg⁺⁺.
3. Calcite and vaterite were formed in those solutions containing no Mg⁺⁺. The ratio of vaterite in CaCO₃ increased at larger rate of deposition. Mg⁺⁺ seemed to restrain the formation of vaterite.

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In this study atomic absorption spectrometry was employed for determination of the amount of lithium contained in sea salt brine produced by electrodialysis with ion exchange membranes and in bitten produced from the salt manufacturing process. In addition, observation was carried out on the interferences of diverse ions in the brine and the bittern, and on the effects of viscosity of the sample solution upon the determination of lithium.
After the raw sample solution was diluted. to an appropriate degree, the standard addition method was applied, and precise results were obtained without preliminary chemical separation. Lithium was found to be 0.92mg/liter in the brine, and 42.5mg/liter in the concentrated bittern, respectively.
These results indicated that the majority of lithium in sea water was concentrated into the brine and the bittern.

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In conducting the permselectivity treatment of cation exchange membrane by using ‘C-10’, which had previously been reported to be an excellent agent for the treatment, the author carried out a study on the effects of the treatment and the occurrence of water decomposition resulting from an over-treatment.
The results obtained were as follows:
1. The time required for the treatment and the effects of the treatment (expressed by the conventionalpurities of concentrated sea water) could be corelated by a single curve regardless of the conditions of the treatment.
2. The lower the concentration or the temperature of the desalting compartment solution was, the earlier the water decomposition occurred. Under such conditions, the maximum purifies of the concentrated sea water were lower, accordingly.
3. There was a linear relationship between the maximum purity and the electric conductivity of desalting compartment solutions independent of the concentration of a treating agent.

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In his previous paper, the author reported that sodium hexameta-phosphate was an effective inhibiter on the thermal decomposition of carbonates in the brine produced by the ion exchange membrane method.
In this paper, the author made a study on prevention of the scale deposition of calcium sulfate hemihydrate and sodium penta-calcium sulfate (Na₂SO₄·5CaSO4··3H₂0) during salt manufacture by the ion exchange membrane method. For scale prevention were used various additives such as ortho- (SOP), pyro- (SPP), tripoly- (STP), hexameta- (SHP), and ultra- (SUP) phosphates. These phosphates were added to the decarbonated brine together with the suspension of calcium sulfate dihydrate. The brine vessel was immersed in a shaking bath at 95°C.
The results of this study were as follows:
1. When the inhibition effect was viewed from the P205 contents of condensed sodium phosphates mentioned above, the SHP and SUP having larger contents than the others indicated a higher inhibition effect. The inhibition value of the SHP was 56 (CaSO₄ ppm/added phosphate ppm) after one hour.
2. The results of X-ray diffractometry, DTA, TGA, and chemical analysis of the deposited crystals showed that when the SHP was added more than 50 ppm, CaSO₄·2H₂0 was transformed into II·CaSO₄ and that when the other condensed sodium phosphates of 50 ppm were added, CaSO₄·2H₂0 was transformed into CaSO₄·1/2 H₂O or Na₂SO₄·5CaSO₄·3H₂0.
3. When one hour passed after the addition, the concentration of the SHP and the SUP showed a decrease of less than 20% against the initial concentration as the result of their decomposition to insoluble phosphate. The other condensed sodium phosphates, on the other hand, showed a decrease of 75-95%.
4. The above results made it obvious that the SHP had a large inhibition effect and transformationeffect from CaSO₄·2H₂0 to II·CaSO₄, and that the SHP was the most effective of all the condensed sodium phosphates.

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