The present authors reported in the present paper the result of studying on the hydrothermal decomposition of solid bittern (MgCl₂·6H₂O), which is one of their studies on by-products of salt making, e. g., gypsum (CaSO₄, 2H₂O), magnesium hydy-droxide (Mg (OH)₂), magnesia (MgO), solid bittern (MgCl₂·6H₂O), etc. The main points ares ummarized as following: (1) Solid bittern w as heated in fused silica retort by heating at several temperatures, i. e., 350, 400, 450, 500, 550 and 600°C, for 60-150 minutes, during which live steam waspassed (2) Hydrochloric acid and steam vapour from the tetort were cooled and condenced to hydrochloric acid solution of nearly about 15-20% concentration (3) The decomposition percentage was chiefly dependent on heating temperature and steam blowing. The highest decomposition percentage 95-98% was obtained by heating at 600°C and 50-70 minutes steam blowing.(4) The decomposed magnesia residue was analysed and determined to be (3-8)MgO: MgCl₂:(0.3-3)MgSO₄, and then testd to be able or not to be used as magnesia cement. The residue must be mixed with light burned majnesia and magnesium chloride or bittern solution to the proper proportion (6-8) MgO: MgCl₂: (0.2-0.4) MgSO₄.(13-15) H₂O of magnesia cement of good hardening strength.(5) Much more studies must be carried out, e. g.,(a) To determine superior acid proof apparatus for industrial scale operation of hydrothermal decomposition,(b) To study the recycle mixing of some part of deocmpodnsed magnesia residue to virgin solid bittern of crushed grain to the easy, decomposion (c) To study the steam blowing to obtain good decomposition percentage and concentrated hydrochloric acid, etc.(6) The coneenced hydrochloric acid was determined to be very pure, not containing sulphuric acid radical and arsenic (As) trace, which fact shows that this hydrochloric acid is suitable to make “Shoyu” and many kinds of food materials produced by using hydrochloric acid.

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Synopsis To study sone kinds of factors seemed to determine appearent volume of basic magnesium carbonate, drying shrinkage of the cake and influence of crushing condition on the appearent uolume are exermined. Critical moisture content of the cake is about 100% and the stages of decreasing rate of drying are different from the cases of clay and etc. These phenomena are illusirated by secondary basketlike structure of crystals and itsjormation and strength seem to be decided by coucentration of HCO₃ in mother liquid when the crystals deposit. The crushing methods which breakup the structure decrease the appearent uolume.

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The remoual of sulfate ion from sea water by use of HCO_3- form, strongly basic anion exchange resin, Amberlite IRA-410, was examined withbath equilibrium and purification studies.
In the equilibrium study, it was perfomed to study on the equilibrium between HCO₃ and SO₄. The enpirical formula was obtained as follows in the case of RHCO₃+SO₄ and L, the weight ratio of water to resin,=10 log Pso₄=0.28+1.32log Phco₃ where Pso₄ was the ratio of SO₄ in resin to SO₄ in solution.
From this formula and HCO₃-Cl formula on the preuious paper (III) [T. Yamabe and U. Shimojo, Bull. Sac. Salt Science, Japan 8, No.5, 223-226 (1954)], the theoretical removal efficiency of suefate ion proved to be 6.1%, when II of artificial sea water (in conposition, Nacl 30g/l, Na₂SO₄ 4g/l) was treated with HCO_3- fonu Amberlite IRA-410, wet uolume 100cc.

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In the present paper, the results of studies on special fire-proof wall board prepared from special magnesia cement by using sea-water light burned magnesia mided with semi or incompletely calcined (under 750°C) dolomite, calocined (at 700°C) product of tailing from chrysotile asbestos plants, and saw dust were reported. The specimen of this special fire-proof wall board was tested on its fire-proofness and sound absording property, and was determ:ned to be of superior quality by using sea-water magnesia (30-50parts) with semi-calcined dolomite (20-40 parts), calcined asbestos tailing (20-40 parts), and about 50-100 parts saw dust or ood meal.

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Seawater was evaporated at boiling point and weighed. Concentration-factor n=(weight of sea water)/(that of brine + that of deposits), density of brine d, chlorinity Cl‰, and chloro sity y=C1g/l (25°C) were obtained. Mass and volume of brine; evaporate, and deposited sod him chloride were calculated.

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[in Japanese]

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[in Japanese]

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