In Japan, the common salt-producing method with saline was entirely replaced by the new electrodialysis method with ion exchange membrane in 1972. This has resulted in a great change both in the chemical composition and the amount of bittern, the byproduct as well as the mother liquid of NaC1 deposits.
Bromine, potassium sulfate, calcium sulfate, potassium chloride, and various kinds of magnesium chloride are manufactured by evaporating the concentration of bittern.
The author has succeeded in obtaining potassium sulfate through the process of treating ionic bittern.
The apparatus of producing potassium sulfate was connected with a tripple-effect evaporator to form a unified system. In the process of treating decalcium bittern, we have established the processing formula of a greater effect than the sofar evaporation system.
The most important point of this report is an analysis on the preparation of potassium sulfate, K₂SO₄. The details of potassium sulfate preparation are as follows:
Because of the scarcity of natural potash resources in Japan, potassium chloride of low quality had been produced in bittern factories for use as fertilizer for sixty years. The author made a study on the preparation of potassium sulfate from bittern and succeeded fortunately in its industrialization.
The equilibrium diagram of J. H. van't Hoff or J. D'Ans for the five component system of oceanic salt, i. e., Na⁺, K⁺, Mg²⁺, Cl^-, is not suitable for the full explanation of the phase rule phenomenon on the preparation of potassium sulfate.
J. H. van'tHoff treated isothermal equilibrium diagrams of four component system of oceanic salt as the reciprocal salt pair, K₂Cl₂+MgSO₄→K₂SO₄+MgCl₂. J. D'Ans treated oceanic salt as three axies, Mg, SO₄, K₂, and recognized that NaCl saturated in all cases. This phenomenon is so greatly complex that those diagrams conceived by the authorities are not able to explain the fact satisfactorily because Na⁺ cannot change freely and perfectly in the equilibrium diagrams owing to the lack of Na₂. In order to make Na₂, K₂, Mg, SO₄, Cl₂ change freely and perfectly, the author felt it necessary to make use of the diagram of ternary prism system that was first reported by Dr. Shunpei Oka at the meeting of the Society of Salt Science held in Tokyo, Japan in May, 1959.
The author made an investigation on the graphical calculation of phase rule by using Dr. Oka's diagram, and thus devised to apply the calculations to practical use for industrialization. Those graphical calculations obtained from the author's study are shown in this report. The comparison of these graphical calculation data with the actual data of industrialization indicates that they are quite similar to each other in their tendency.
The outline of the actually-industrialized manufacturing process resembles the process employed by Stassfurt salt mine, which manufactures potassium sulfate from decomposition of kalimagnesia with potassium chloride and produces kalimagnesia by the double decomposition of magnesium sulfate with potassium chloride.
Kalimagnesia in this case, therefore, is a kind of medium double salt produced in the two-step reaction process. Magnesium sulfate, MgSO₄·7H₂0 used to be produced from bittern by cooling with refrigerator in the salt-field bittern age. Nowadays, however, as there is not a source of supply of magnesium sulfate in ion-bittern, magnesium sulfate is obtained from magnesium hydroxide by treatment with sulfuric acid. Magnesium sulfate which is now used is of the following chemical synthesis, Mg (OH) ₂+H₂SO₄=MgSO₄+2H₂O.

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The ionic state of uranium in the extraction process of uranium from seawater was estimated from the equilibrium relations. Uranium existed mainly in the cationic state such as UO₂²⁺ or UO₂Cl₂⁺ in hydrochloric acid solution and in the anionic state such as UO₂ (SO₄) ₃^4- in sulfuric acid solution. In carbonate solution or sodium chloride solution containing carbonate, uranium existed in the anionic state such as UO₂ (CO₃) ₃^4-. In the carbonate-free solution of sodium chloride, however, UO₂OH₃^- was predominant. The ionic state in the mixture of hydrochloric acid and sulfuric acid was complex. In this case, such cationic ions as UO₂²⁺ or UO₂SO₄⁰ was predominant in 0.1 N solution, and such ion as UO₂ (SO₄) ₃^4- was predominant in 1.0 N solution.

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An investigation was made on the method of preparing uranium adsorbent from titanic acid and cordierite by making the latter impregnate and support the former by the urea method. Also, the relations between the amount of uranium adsorbed in the prepared adsorbent and its property values were investigated. To prepare adsorbent having a high adsorption capacity, it was important for the mother liquid to have pH of around 8 and for the cordierite to have a specific surface area larger than about 700m²/g per titanic acid. As the result of the above investigations, such conditions as the concentration of titanium, the amount of urea to be added into the prepared solution, etc. necessary for meeting the above requirements were made clear.
The amount of uranium adsorbed in the adsorbent measured by a simple method for granular adsorbents after two-day impregnation was 40 to 50μg/g when the support had a specific area of 2m²/g and a grain size of 0.35 to 0.42mm. In case the support having a specific surface area of 8m²/g was used, the adsorbent showed the possibility of saturated adsorption up to approximately 600μg/g.
This granular adsorbent was found suitable for use in a fluidizing adsorption equipment. Therefore, a recovery plant of uranium from sea-water by the dispersion and deposition method was shown as an example of its application.

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