The authers determined the constituents of brine obtained by extraction of salt catching sand (Kansa), colected after the sand surface evaporation of sea water, with water, sea water and brine.
The extraction rates of salts were varied in the order of MgCl₂. KCl, MgSO₄, NaCl, CaSO₄, and decreased with the concentration of brine respectively.

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We are manufacturing caroallite from refrigerated de-sulphate bittern by vaccum pan concentration.
From this special carnallite, there was obtained directly potassium chloride containing 88%-90% KCl by means of extracting with steam and CaCl₂solution, without recrystallization of carnallite. The yield was comparatively good.

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In this Paper, the values, being required in the design and operations of sloping salt-field,(i. e. concentration ratio, quantities of brine and sea water, bed length etc.) are calculated, basing on the data observation at Hofu Salt Experiment Station.

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These researches were carried on to accomplish a purpose of producing Mg(OH)₂ with low contents of Ca residue (less than 2% as CaO) from bitter brine and dolomite milk and also to get about twice yield of the product more than from milk of lime by the general method.
In the previous 1 and 2 (This Journal 1954, 3, 125-429), chemical composition and optimum calcined temperature of 2 kinds of dolomite (from the famous dolomite bed at kuzuu in Tochigi pref. and from a new one at Irino in Okayama Pref.) had been compared. The results were as follows.
(1) Each of 2kinds of dolomite was calcined at diffarent temperature from 800°C to 1200°C and the degree of “temperature increase” by hydration heat was compared. Kuzuu dolomite showed the maximum “temperature increase” in case of calcination at 1100°C, but Irino dolomite at 1000°C.
(2) Slaked dolomite milk, which was obtained from the dolomite calcined at its optimum temperature, had in all cases the minimum settling velocity in water. This is also to be able to make emulsion of dolomite milk suitable as raw material for manufacturing Mg (OH)₂.
(3) As described in part 2, the eff act of preservation in air was also minimum in the case of dolomite clinker calcined at its optimum temperature.
On the other hand, this effect was eminent in the case of calcined at lower temperature(e. g. 800°C or 900°C), never the less it could be diminished by calcining at the same temperature for a longer time.
In the case of calcined at higher temperature (e. g. at 1250°C), the temperature increase by hydration heat became small and slow, which would be attributed to its inactivated result.
(4) The amount of residue seperated from slaked dolomite milk increased after the preservation in air. Now in this paper 3, the rate of filtration of Mg (OH)₂ precipitate and its settling speed in water were compared in order to best condition for manufacturing Mg (OH)₂, and the authors found that the velocity of addition of alkali solution gave an eminent influence to the rate of filtration and settling speed of the product. The experimental results were as follows.
(1) When alkali solution (e. g. NaOH in this paper) was dropped in step by step, the rate of filtration of Mg (OH)₂ and also its settling speed became very fast,then separation and washing of reaction product became very easy.
(2) This advantage of dropping method was more effective in the beginning of the reaction.
Therefore it was better to stop its dropping at about a half equivalent of alkali to Mg ion in bitter brine.
(3) As for effect of concentration of reaction material the easiness of filtration increased as it was diluted.
(4) As for effect of reaction temperature,there were optimum interval of temperature. In general dropping at room temperature was more effective than at other temperature.

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The scale prevention is one of the most impotant problems in salt-production. Nowadays, the “Bittern-Pouring method” is widely used in Japan, but this method is accmpanied by many unfavorable facts. Under these circumstances. We find out the new scale prevention method. We name this “Addition of crystal seeds”. This method can be applied not only to the vacuum evaporation system, but also to the auto-vapour compression system.
.We have obtained remarkable results by using this new prevention method, for example, concentrating brine (at about Bé 19°) 72 hours continuously, scale adhered to the heating pipe is practically zero. Nevertheless, the cost of applying the new method is negligible.
This report consists of two experiments, Experiment-1 is the small scale and Experiment-2 is the larger one. From these experiments following conclusions are known:
(1) Concerning the kind of seed crystals, nothing is more effective than calcium sulfate and its hydrates.
(2) Concerning the water of crystallization of calcium sulfate hydrate, the same hydrate as rystallized at its evaporating condition is most effective.

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