A study was conducted on the determination of a small amount of ferrocyanide in sodium chloride by spectrophotometric method in which ferric chloride and citric acid were used, The results obtained from this study were as follows:
1. The optimum condition of measurement was at 710mμ. with 50mm cells.
2. The maximum absorption was obtained at temperatures below 20°C after standing over 22-25hours.
3. Little influence of sodium chloride was observed on final color formation.
4. Potassium ferrocyanide over 1 ppm in 20% sodium chloride solution was determined with errors within 20%.
5. Heavy metals, chiefly Zn²⁺ and Cu²⁺, in domestic salt hindered the solution from color for-mation. These metals were removed by treating with ion-exchange resin in ammoniac solution.

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A study was conducted on the behavior of phosphate in the concentrating process of sea water. The behavior of phosphate was traced by using radioactive isotope, ³²P. Phosphate in sea water was spectrophotometrically determined by phosphomolybdate method after it was separated from other elements by coprecipitation with ferric hydroxide.
When the evaporating temperature was kept below 80°C, the loss of phosphate from the sample solution was negligible in the early stage of concentration. On the other hand, the phosphate transferred rapidly into the deposit, when more than 70% (in volume) of sea water was evaporated.
In the case of evaporation at temperatures more than 90°C, phosphate started to deposit in the early stage, but the precipitation rate was not so high as in the case mentioned above.
The depositing tendency of phosphate was more remarkable than that of strontium or calcium.

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This paper describes the behavior of strontium in bittern shown when the strontium is precipitated as carbonate, oxalate, and phosphate. In this study, sodium carbonate, sodium oxalate, sodium phosphate or sodium hydroxide was used as precipitant. The behavior of strontium was traced by using radioactive isotope ⁸⁹Sr, while calcium and magnesium were determined by EDTA titration.
When sodium carbonate and sodium oxalate were used as a precipitation agent, the behavior of strontium and calcium were almost the same. When sodium oxalate was used, the precipitation ratio of strontium was the most remarkable. In the case of adding sodium oxalate of 0.6 times as much to the equivalent quantity of calcium and strontium in brine, approximately 60% of them were deposited, but the precipitation ratio of magnesium was extremely small. When using sodium phosphate, on the other hand, the precipitation ratio of strontium was higher than those of calcium and magnesium. When sodium hydroxide was added to brine, a portion of strontium was considered to coprecipitate with magnesium hydroxide. After the deposition of magnesium in brine reached more than 90%, the deposition of calcium became rapid, and the precipitation ratio of strontium was about 56%.

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In the previous paper [Sci. Papers Centr. Res. Inst., Japan Monop. Corp., Nos. 105,229 (1963)], the Compostion of salts deposited by the concentration of raw bittern was studied by chemical analysis and X-ray diffraction.
In the present paper, the author conducted an experimental study on the concentration of desulfurized bittern by adding carnallite for the purpose of extracting potassium chloride from bittern. The results thus obtained were as follows:
(1) In the early stage of evaporation, the compositions of the mother liquor well coincided with the equilibrium diagram of the four-component system, MgCl₂-NaCl-KCl-H₂O, but the coincidence became worse toward the end of evaporation.
(2) The content of potassium chloride ranged from 71.6 to 73.1g per 100g of the salt deposited by concentration and from 88.4 to 91.8g per 100g of the salt washed with saturated potassium chloride solution.

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The previous paper [This Journal 18,276 (1965)] reported that the composition of salts deposited as the result of this concentration of desulfurized bittern mixed with carnallite was studied and that the potassium salt was found to be deposited as potassium chloride.
The present paper gives a description on the study that was conducted by chemical analysis on the composition of mother liquor and of those salts deposited by the cooling of desulfurized bittern mixed with carnallite at 0°C. The results obtained were as follows:
(1) Potassium salt deposited was found as potassium and/or carnallite, and the ratio of the potassium salt was decided by the amount of carnallite added.
(2) When a small amount of carnallite was added to desulfurized bittern, potassium salt was deposited as potassium chloride. For example, when 40% carnallite was added to desulfurized bittern, the potassium chloride content of the deposited salt was 91.13%.
(3) The compostion of the mother liquor coincided with the result of D'Ans's equilibrium diagram of the four component system, MgCl₂-KCl-NaCl-H₂O at 0°C.

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