For the purpose of examining the behavior of carbonates in the concentrating process of sea water, the author carried out experiment on the natural evaporation and the boiling-point evaporation of sea water at atmosphere. Also, he analyzed various samples of brine and scale taken from the flowing-down system salt-field, the salt making evaporator, and the flash-evaporator for desalination. The results obtained were as follows:
1. The whole content of carbon dioxide in brine during the concentration of sea water by natural evaporation was the largest in the brine density of 1.06-1.18, and the content of its CO₂was 80-85mg/1 brine.
2. The deposition ratio of carbonate in the concentrating process of sea water was 27-90% for the natural evaporation, and 49-99% for the boiling-point evaporaion at atmosphere.
3. As the result of examination of the saturation index of brines, the acid injection method proved to be the most effective one for prevention of alkaline scale than the additive treatment and seeding method.
4. The constituent of scale deposited in the flash evaporator for desalination was determined bychemical analysis, DTA, TGA, and X-ray diffractionmetry.

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With regard to the static characteristics under the partial load condition of the saline water conversion plant operated by Multi-Stage Flash (MSF) type brine recirculating evaporator, a briefanalysis was executed by utilizing computer program for general process simulation. Prior to execute the calculation, we had set equations to decide the condensing capacity of an evaporator-condenser which would give much influence to the performance of MSF evaporator. It was shown in the equations that the operating conditions of various loads should be decided by the heat and material balance under the condition exactly corresponding to thecondensing capacity. The outline of this calculation program was described in the paper. A model plant for the calculation was assumedas below:
Capacity of distillate produced: 1000 T/D (24 hrs.)
Number of stage: 10 (Heat Rec. 8, Heat Rej. 2)
The result of analysis indicated that an operating range of MSF evaporator under the partialload was limited within a short range due to the restriction of brine-flowing condition in each, inrelation to brine levels and brine orifices mounted between stages of the evaporator. The extent of the range depended on the number of stages and the configuration of the flash chamber of the evaporator. In the case of the model, for instance, the operating range of the maximum brine temperature under 80 percent of production rate was between 110.0 to 111.5°C (1.5°C difference).
The result of analysis also showed that when the maximum temperature of brine was lower than the above condition, the levels of brine were over the maximum allowable one, and to the contrary when the temperature was higher, the levels were unsealed. In either case, these phenomena proved a hindrance to the operation of the plant. In addition to the above, the following results wereobtained from the analysis of the model:
(1) With a decrease in the load (distillate), most of such operating quantities as recirculating brine, heating steam supplied, maximum brine temperature, etc., showed a decrease respectively, but the quantity of raw sea water increased.
(2) Performance ratio (i. e. distillate (kg) vs. steam (kg)), increased in proportion so a decrease in the loading.
Furthermore, changes in operating quantities obtained when the orifices of brine were adjusted while the load was changed from full to partial, were mentioned for reference

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In order to recover potassium from sea water and brine, a study was made on the effects of mixed ratios in the preparation of exchangers. Results were as follows:
(1) The degree of crystallinity varied with an increase in the mixed ratio of phosphate or polyphosphate to zirconium at the time of preparation, and it became more crystalline gel from themost a morphous gel.On the others hand, the ion selectivity changed in proportion to the variation of crystallinity.
(2) It was found that the ion exchange reaction indicated two different reaction forms accordingto the mixed ratio at the time of preparation. The first one was Na⁺>K⁺>Mg²⁺-Ca²⁺when the adsorption was evaluated by mg/g exchangers, and the second one was K⁺>Na⁺>Mg²⁺-Ca²⁺.
(3) The selective adsorption property was classified easily by apparent volume of wetexchangerjust like the results of our study reported in our previous papers.

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In order to obtain the basic data for processing the bittern produced from the brine made by evaporation with ion exchange membrane, it is necessary to examine the existence of the chemical formula of the double salt composed of potassium chloride and calcium chloride.
It has so far been reported by Lightfoot and Assarsson that only one double salt exists in the system of KCl-CaCl₂-H₂O·Lightfoot has reported of 2 KCl-CaCl₂-H₂O, while Assarsson has reported of KCl·CaCl₂·
However, after the authors examined their reports, they found the inconsistence:(1) KCl·CaCl2 has been reported to exist at 50°C and 2 KCl·CaCl₂·2 H₂O at 75°C, and (2) the both reports have mentioned the equilibrium values of the solution of each double salt at 95°C.
From the results of our residual method and X-ray diffraction, the authors reached the conclusion that only KCl·CaCl₂existed as the bouble salt of potassium and calcium chloride.

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