In Japan, the salt manufacturing method from sea-water was completely changed on January 26th, 1971. The traditional and time-honored salt-making fields were all abolished, and a new salt-making method by electrodialysis with ion-exchange membranes was adopted instead.
Those ionic brines obtained from the new method have special compositions. Namely, they contain little SO₄^2-, and the proportion of each ion vary from another. So, it is quite difficult to find out regular relations among them. If the small content of SO₄^2- be neglected, however, they may be treated with the five-component system Na⁺, K⁺, Mg²⁺, Ca²⁺||Cl^--H₂O.
The five-component system already reported at various temperatures, contains relative few kinds of crystals as the solid phases, and at least it does not cause serious super-saturations till the saturation of KCl.
On the other hand, the brine produced from the traditional salt-field contains almost the same proportion of salt as in the sea-water. It must be treated with the five-component system of oceanic salts; Na⁺, K⁺, Mg²⁺||Cl^-, SO₄^2--H₂O. This five-component system contains SO₄^2- which is liable to yield many hydrated salts and compound salts, often causing serious super-saturation. Therefore, it is hard to do the graphical calculations, and the results obtained often differ from the experimental results.
From the above-mentioned points, the author came to the conclusion that the electrodialysis method was most suitable for the graphical treatment with the phase diagrams. In the present paper, a study was made on the reliability of such treatments.
The evaporations of four ionic brines at the three different temperatures of 110°C, 70°C and 45°C were calculated in a graphical way. For such calculations upto the saturation of KCl, trian-gular coordinated diagrams of Jänecke type simplified to be always saturated with NaCl, were used. The concentrations of NaCl and H₂O were not shown on such diagrams. To get the concentrations of these components. therefore, an interpolation method was used by presuming that the contents of NaCl and H₂O would change linearly on the straight lines of the diagrams. For the calculation of their evaporations upto NaCl saturation, the orthogonal projection of diagrams on the tetrahedron coordinate were used. The contents of water were calculated by the interpolation method as mentioned above. Also, the calculation of the same evaporations was done by the empirical formula developed by the Japan Monopoly Corporation. The results of the above two calculations were shown in Table 3. The calculated items were as follows: Water evaporated to the saturation of NaCl:E_s, the quantity of NaCl saturated brine:W_s, water evaporated from NaCl brine to KCl brine:E_b', NaCl deposited:Sb', the quantity of KCl saturated brine:Wb', and the total water evaporated to the KCl saturation: E_s+E_b'.
The study of Table 3 showed that the graphically calculated E_s was larger than the empirical formula value by several percents. Because of this fact, the graphically calculated W_s and Eb' were several percent smaller. However, both the values of S_b' and E_s+E_b' coincided very well. Accordingly,S_b' and E_s+E_b' were considered the most important values for the salt-making factory. The fact that the results of the two methods coincided in these important values, indicated that the graphical method was as reliable as the empirical formula method authorized by the Japan Monopoly Corporation.

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昭和47年度から本格的に稼動を開始したイオン交換膜法による生産塩の不純物の量と存在形態を検討し, 塩田法当時の値と比較検討し次の結果を得た. なお粉体物性についてもあわせて測定した.
1. 最近7年間の国内産塩の分析結果から, 並塩では, 塩化ナトリウム純度が96.4%から97.4%まで順次向上し, 水分, マグネシウムおよび硫酸イオンは順次減少した. イオン交換膜法になってからはマグネシウムおよび硫酸イオンが減少し, カリウムイオンが増加した. 食塩では塩化ナトリウム純度は変化しなかった. イオン交換膜法になってからは, 硫酸イオンが減少しカリウムイオンが増加したほかは顕著な変化がなかった.
2. 結晶中の不純物については, イオン交換膜法産塩は塩田法産塩に比較して, 塩化ナトリウム以外のイオン量の総計が0.045～0.13%から0.07～0.23%と増加した. すなわちカリウムイオン, カルシウムイオンおよび硫酸イオンは多くなり, マグネシウムイオンは減少した. なお, 液泡中の水分は少なくなった.
3. Jäneckeの三角図表で原料塩および洗浄塩の不純物組成を整理すると, 原料塩の不純物組成はいわゆる塩カル系であるが, 結晶中の不純物組成はいわゆる硫マ系となる. これらの検討結果から, イオン交換膜法による結晶缶内では, 硫酸カリウムあるいは硫酸ナトリウムを含む結晶が析出し, 結晶中にはいることが推定された. またカリウムイオンがナトリウムイオンの代わりに結晶格子内にばいることも推定された.
4. イオン交換膜法産塩の25℃における臨界湿度は, 食塩では37～38%R. H., 並塩では68～73%R. H. であった. また試料10gを純水30mlに溶解した溶液のpHは, 前者では7.4～8.5, 後者では5.3～8.5であった.
5. 食塩の粉体物性は, 平均粒径; 290～390μ, 見かけ密度; 粗充填1.25～1.41, 密充填1.37～1.46g/cm³, 安息角;41～46°, 内部摩擦角; 33～40°であり, 並塩の値は, 平均粒径; 280～400μ, 見かけ密度, 粗充填0.75～0.86, 密充填1.21～1.31g/cm3, 内部摩擦角; 36～40°であった.

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蒸留法による海水淡水化プロセスでは, プラントの金属材料の腐食を防ぐため, ブライン中の溶存酸素濃度を10μg/l程度にしている. この微量溶存酸素をウィンクラー法で定量する場合, 試料溶液中の酸化還元物質による定量への影響が指摘されている. そこで鉄 (III), 鉄 (II), 銅 (II), 硝酸および亜硝酸の各イオンによる定量への影響について, まず純水を用いて実験し, そして妨害イオンには対策を講じた. 次に海水を用いた実験にこの対策を適用して良好な結果を得た. 鉄 (III) イオンにはリン酸溶液の使用, 鉄 (II) イオンには塩酸o-フェナントロリン溶液の添加および亜硝酸イオンにはアジ化ナトリウムの添加により, 定量への影響を除いた. 銅 (II) イオンと硝酸イオンによる影響はほとんどなかった.
なお実験に必要な微量溶存酸素溶液は試作した装置で簡便に調製した.

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This study was conducted to examine the validity of phase diagrammatical method on the separation and utilization of oceanic salts in sea water.
There are various methods for the separation and utilization of oceanic salts which are complicated salt solutions. However, it must be considered that the multiphase equilibria in salts and water systems such as mixed salt solution treatments are accompanied by phase transition.
Therefore, the author devised the method of surmising various qualitative and quantitative relations in the case of solution treatment, under a phase rule analysis by drawing the equilibrium diagrams of the five-component system in oceanic salts and by making graphical calculations including the samples and conditions. The validity of this graphical method was confirmed by experiments.
The drawing of the equilibrium diagrams, the graphical calculations and the experiments were carried out on the preparation of potassium chloride from carnallite and on the preparation of potassium sulphate from bitter, especially for the purpose of recovering potassium salts.
As the result of the study, the author found theoretical relations on the optimum conditions, yields, etc., which have not been made clear yet by the oceanic salt industry depending on just experiences.
The results of the author's diagram-drawing, graphical calculations and phase rule analysis coincided fairly well with the values actually determined. Thus, the method proposed by the author was proved to be valid and useful.
The conclusion of the author was that the method was fairly reliable and could be used for making judgements, estimations and fundamental operation in the case of planning of factory manipulation, investigation, etc.

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