Among various methods to increase the purity of common salt, the washing method is simple and was considered suitable to the factories in Japan, then we studied the effects of the washing method using saturated salt solution or brine, to increase the purity by the removal of impurities such as calcium or magnesium in the salt.
The following results were obtained.
(1) The magnesium is removed almost perfectly from the salt by the washing, but the calcium is removed 50-70% of total calcium.
(2) There are a proportinal relation between the magnesium contents of the washing liquid and the washed salt.
(3) The effect of the times of washing or the quantity of washing liquid is not great.
(4) The purity of the washing salt is increased on drying as comparable to the quality of “Refined Salt”.

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The scale crystallized from the salt-field brine consists of the calcium sulfate principally and sticks to every part of the bamboo twig of “Shijoka”, the thread of “Net Type” and the transport pipe of the brine.
As there were few investigations of the scale crystallized from the salt-field brine. We studied the problems of the scale sticking, the scale elements and the scale dissolution, and obtained the results as follows.
1. The annual scale thickness was about 2mm by sticking to the bamboo twig of “Shijoka” and the thread of “Net Type”.
2. The scale elements were CaSO₄ of 75%, moisture of 20% and etc.
3. When the scale was soaked in the sea-water, the weight of the dissolved scale in the sea-water was 0.067gr/cm² from the surface of the scale a day.

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1. The molybdenum content of solar salts and home product salts were determined colorimetri-cally by the thiocyanate-stannous chloride method after being collected by adsorption with ferric iron and ammonia at the pH3-4.
2. Analysis showed that the molybdenum of solar salt is distributed substantially in the insoluble matter, and that the mean content is about 0.03ppm, while, it is almost negligible in the water soluble part.
On the contrary; in home product salts, the molybdenum is contained rather in water soluble part than in insoluble part, and is slightly much as compared with solar salt, unlike the case of another metals such as titanium, cobalt, nickel, chromium or vanadium.

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The waste of saltworks is called “Scale” and known to be constituted with dihydrate, hemihydrate and anhydrite of calcium sulfate, which deposits with sodium chloride during evaporation of the brine according to its boiling point. The scale of a quadruple effect evaporator was observed by microscope, analyzed by X-ray diffractometer, and treated with sodium chloride solution in order to obtaine the crystalline gypsum (dihydrate of calcium sulfate).
Results of experiments were as follow; The scale of No.4 evaporator was considered to be constituted with dihydrate of calcium sulfate and used as seed crystal to converting the scale of No.1 evaporator into dihydrate. The scale of No.2 and 3 evaporator was considered to be in almost all hemihydrated and converted into dihydrate in sodium chloride solution readily.
The scale of No.1 evaporator was considered to be anhydrite and converted into dihydrate only with difficulty. But the conversion was proceeded easily by adding the seed crystals of dihydrate.

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In previous paper, it was stated that the scale of quadruple effect evaporator at saltworks was converted into dihydrate of calcium sulfate by treating with sodium chloride solution readily, of which that of No.1 evaporator was hydrated readily by adding seed crystal of the dihydrate ot the solution.
In this study, the growth of crystal of gypsum produced was taken into consideration at the time of treatment of the scale with salt solutions (Nacl-, HCl-solution, bittern and desulfated bittern), namely, the scale of No.2 and 3 evaporator was considered to be in almost all hemihydrate and was added successively into the salt solutions suspending the seed crystals of calcium sulfate dihydrate, which was maintained at a proper supersaturation without nucleation, and the scale of No.1 evaporator was considered to be a mixture of hemihydrate and anhydrite of calcium sulfate, of which the hemihydrate was treated as above mentioned and the anhydrite was stirred with the dihydrate produced in the solution. Addition rate of the scale and the form of gypsum produced was shown.

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As the quality of boiler water determines whether the accident such as the corrosion results or not, the treatment of boiler feed water must be performed adequately, and many investigations have been repeated about it.
Many kinds of chemical agents are tried and used, and the ion exchangers play the important role concerning the purification of water. The investigation and comparison of the properties of these ion exchangers is necessary, if a proper selection should be made, therefore many ion exchangers, both foreign and domestic, and collected and are compared in the properties, such as the ion exchanging ability, the mechanical wear and the solubility to water. Organic ion exchange resins were superior to inorganic ones in many respects.

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