A study was conducted on manufacturing, from magnesium hydroxide (Mg(OH)₂) suspension and ammonium bicarbonate (NH₄HCO₃) solution, magnesium carbonate (MgCO₃·3H₂O) which is raw material used for manufacturing basic magnesium carbonate as heat insulator pipes and boards. The following formula was used for this study:
Mg(OH)₂+NH₄HCO₃+2H₂O=MgCO₃·3H₂O+NH₄OH
The method adopted consists in mixing 15% Mg(OH)₂ suspension and 15% NH₄HCO₃ solution at the temperature of 40-50°C for 30 minutes. The shape of MgCO₃·3H₂O crystal prepared by the above mentioned method was of a needle type and similar to that prepared by the magnesium chloride (MgCl₂) method. The former crystal, however, was smaller and thinner than the latter.
MgCl₂+Na2CO₃+3H₂O=MgCO₃·3H₂O+2NaCl (MgCl₂ method)
According to the X-ray diffraction and chemical analyses conducted, some Mg(OH)₂ particles were found in the product obtained by this new method. The products of basic magnesium carbonate manufactured by these two methods were almost the same in physical and chemical properties, except for the results obtained from the differential thermal analysis.

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This study was conducted to obtain fundamental data to be used when adopting the gas hydrate process for the concentration of sea water or brine.
A double-walled testing vessel was first vacuum evacuated, and a given amount of sea water or brine was poured into the vessel and was cooled with liguid ammonia until its temperature reached a fixed degree. After R-12 or R-22 gas was put into the vessel to raise pressure up to a fixed degree, hydrate crystals were formed by stirring the sea water or brine. By determining the amount of Cl contained in the mother liquor, studies were conducted on the forming of hydrate and the concentration of brine. Thus, the following results were obtained:
(1) The hydrate forming lines of R-12 gas were determined with the brine ranging from 0° Bé to 9.2° Bé, and those of R-22 gas were determined with the brine of 3.1° Bé.
(2) As to the contacting time of sea water with gas and the forming of hydrate, it was found that under the conditions of 5°C, 1.6kg/cm²·G and 800rpm, hydrate began to form in about two minutes and showed a rapid increase in quantity for the first five minutes, but it gradually declined its increasing rate later.
(3) The concentration of brine showed an increase in proportion to the increase in the number of revolution in the range of 200-1,000rpm, but the increasing rate gradually declined in the case of 400rpm or over.
(4) The rate of hydrate forming reaction with greater thermal driving force was found higher in the early stage but showed a gradual decline later, On the other hand, with smaller thermal driving force, the rate of reaction was found lower at first but indicated a smooth increase later.

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This study was conducted to obtain data regarding the free-flowing quality of Kitchen Salt (salt for alimentary use) produced in various salt making plants.
First, experiments were carried out to investigate the relationship between the free-flowing quality and the physical and chemical properties of each salt, and the following results were obtained:
1) It is possible to know the degree of free-flowing of salt by measuring the angle of repose or the free-flowing volume.
2) The larger the particle size of salt becomes and the more calcium carbonate is added, the better the free-flowing quality of the salt becomes, In addition, the less the moisture content
3) It was found that there was a high degree of correlation between the angle of repose aud the apparent density (the most coarse) when the moisture content of the salt was less than 1%.
As the result of the continued investigation on the free-flowing quality and the physical and chemical properties of each salt, it was also found that the free-flowing quality was insufficient in general and showed a difference according, to the plant, However, it was found possible to evaluate the free-flowing quality of salt by measuring the apparent density as there existed correlation between the free-flowing quality and the physical and chemical properties.
In addition, it was found that free-flowing of the Kitchen Salt were improved remarkably by removing the microscopic salt up to about 150μ and by decreasing moisture content under 0.1% or by adding 0.3-0.4% of calcium carbonate to the salt.

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Various fundamental experiments were carried out to determine the most appropriate quantity of silica gel to be used for table salt as a moisture preventive agent, and the following results were obtained:
1) The limit of moisture content for the free-flowing of salt was approximately 0.4%.
2) The amount of moisture absorption or exhalation of table salt contained in a vessel without a cap was proportional to 0.79 power of the difference between the critical relative humidity of sodium chloride and the humidity of air at 20°C.
3) When the table salt was left in a vessel without a cap in the relative humidity of 84% and the temperature of 20°C, it could not be used any more after 15 days because of the increased moisture content.
4) The velocity of moisture absorption of silica gel through the layer of salt decreases to about 1/2 or 1/3 of the velocity obtained in the open state.
5) The average humidity of a kitchen of a Japanese house is higher than the humidity of outdoors, and most of the Japanese houses have the relative humidity amounting to more than 75%.
The results of the above experiments showed that it was possible to prevent the absorption of moisture by charging 3 or 4 grams of silica gel to the bottom of the vessel. Also, it was found that the results of a practical test agreed with the estimated trial values.

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[in Japanese]

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