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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にがり中のカリウムイオンをラングバイナイトのような複塩の形態でなく, 濃縮して直接塩化カリウムを採取することを目的とし, 脱硫にがりにカーナライトを添加して濃縮し, 析出塩および母液の組成を調査したこ. 結査は次のとおりである.
(1) 濃縮段階の初期の母液(脱硫にがり100gにカーナライト50gの割合で加えて濃縮し, 蒸発水量が10,20,30mlまで濃縮して分離したこもの)の組成点は110℃および25℃ともにMgCl₂-NaCl-KCl-H₂O系のその温度における溶解度線によく合致した, しかし, 濃縮度の高いもの(蒸発水量が40および50mlの場合)は合致しなかつた.
(2) 析出塩中の塩化カリウムの含有量は71.6～73.1g/100gの値であつた. また, 塩化カリウムの飽和溶液で洗浄して得たこものは88.4～91.8g/100gの値であつた.

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脱硫にがりにカーナライトを加え0℃に冷却した場合の析出塩および母液を分離してその組成を調査した.結果は次のとおりである.
(1) カリウム塩は塩化カリウムおよびカーナライトとして析出し,析出率は主としてカーナライトの添加量によつて決定した.
(2) 脱硫にがりに少量のカーナライトを添加する場合はカリウム塩は塩化カリウムとして析出する。たとえば脱硫にがりに対して40%のカーナライトを添加した場合の析出塩中の塩化カリウムの含有量は91.13%であつた.
(3) 母液の組成は4成分系MgCl₂-KCl-NaCl-H₂O系の0℃の平衡図による考察結果とよく合致した.

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