Some of the electrolytic conditions for the bittern with sodium hydroxide addition were studied, i. e. anode current density (DA) which may cause corrosion and heating of PbO₂anode, and cathode current density (DK) which may deterinine the available chlorine in magnesium bleaching powder, and temperature of electrolysis which may govern the rate of magnesium bleaching powder formation and CIO^-ion concentration.
The optimum DAof PbO₂anode was found to be less than 0.2A/cm², with which DA, no corrosion and heating of the PbO₂anode was observed. The effect of DK on the available chlorine content was remarkable, and crystalline and easily filterable magnesium bleaching powder of good quality, with about 44% available chlorine, was obtained at DKof less than 0.2A/cm².
The optimum temperature of electrolysis was found to be about 30°C. A larger scale apparatus of 20A input was constructed and comparable good results were obtained.

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In their previous paper (This Journal, 14, 227-34,(1960)), the authors computed graphically the isothermal evaporation of the natural gas brine at 25°C by means of equilibrium diagram of the five-components system: NaCl-KCl-MgCl₂-CaCl₂-H₂O. Since the natural gas brine contains much more NaCl compared with the other salts in the solution, the NaCl crystallizes out first, and comes out continuously over the whole course of evaporation. Therefore, the equilibrium diagram may be simplified by assuming the system to be always saturated with NaCl, as in the case of oceanic salts treated by van't Hoff.
In the present paper, two kinds of such simplified diagrams were drawn, one on the triangular cordinate and the other on the stereogeometric axis, and the change of liquid phase compositions were computed graphically. To draw the diagram on the tetrahedron cordinate, as previously reported, 23 points were necessary, while the present simplified diagrams need only 11 points, which are less than half of the former ones. The drawn diagrams were of course, less complicated, and the graphical computations much easier. By comparing the resultant values for 5 points computed by means of 3 different diagrams, namely one on the triangular cordinate, one on the stereogeometric axis and one on the tetrahedron cordinate, the authors found out fairly good coincidence among them. Especially, the values gained with triangular cordinate were found to coincide almost completely with the ones gained with the normal tetrahedron cordinate.
From these reults, the authors concluded that the diagram on the triangular cordinate was best suited for such calculation.

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Vol. 14 (1960) No. 5 p. 228-232

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A small quantity of boric acid is often absorbed into magnesium hydroxide crystals precipitated by the reaction between bittern and milky lime. Concerning this phenomenon, some studies have already been reported on production of magnesium hydroxide through absorption of boric acid to its crystals (Bulletin of the Society of Salt Science, Japan 14, 234, 275 (1960)).
The present authors studied on some of the effects of the boric acid as mineralizer to the thermal properties of magnesia clinker produced by firing such magnesium hydroxide.
The results were summarized as follows: boric acid easily dissolved into the crystal lattice of periclase at high temperature, as easily as silicon oxide and ferric oxide a solid solution contained boric acid was quickly formed among periclase particles at a temperature lower than the usual firing temperature of clinker, and its constructure was more stable than that of solutions of other components. By X-ray analysis, the mineralogical composition of bond part was found to be mainly Mg₃(BO₃)₂. If the absorbed amount of boric acid was increased by more than 1.0 per cent as B₂O₃, the themal properties of the clinker would deteriorate remarkably with the increasing volume of bond part.
Sea water magnesia generally contains a little of lime, silica, alumina, ferric oxide etc., as impurities. The absorbed boric acid was found to form several complex double salts with these components which in turn that phase promoted crystallization of periclase.

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(1) 各種無機塩類の単独飽和溶液の組成および蒸気圧に関する既存のデータについて調査した結果, 一般的な関係が存在することを知り, この知見に基ずいて混合飽和溶液の組成と蒸気圧に関する数ケの仮定を立てて検討した. 実験は湿度を測定する間接的な方法であり, 簡便な装置を考案して用いた. 実験誤差は全データについて±2%以内である.
(2) 各種無機塩類の単独飽和溶液における蒸気圧降下ΔPn (mmHg, 脚符号nは塩の種類を示す. 以下同様) とイオン濃度ZnCn (Cnはモル濃度mol/1,000 molH₂O, Znは1分子当りのイオン数) の間には温度をt (℃) とすると, 多少の例外はあるが次の関係がある.
ΔPn=b・10^aZ_nσ_n
a=-0.0000320t+0.00565
b=0.0130・10^0.00734t・Ps
ただし, Psはt℃における飽和蒸気圧 (mmHg) である.
(3) 無機塩類の混合飽和溶液の蒸気圧降下についてはダルトンの分圧の法則に類似した理論が成立する. すなわち, 蒸気圧降下ΔP (mmHg) は各塩の蒸気圧に関する分降下ΔP'n (mmHg) の和に等しく, 式で表わすと
ΔP=ΣΔP'n
である. ただし, 上式において
ΔP'n=C'n・ΔNn
であつて, C'nは混合飽和溶液中における各塩のモル濃度であり, ΔNnは各塩の蒸気圧に関する分子降下であつて下式により求められる.
ΔNn=ΔPn/Cn
ΔPnのtに対する変化は前述のとおりであるから, ΔNn, ΔP'n, ΔPのtに対する変化も全く同様である.
(4) 食塩その他の無機塩類の結晶において不純分がその吸放湿性におよぼす影響は, 従来定性的にばくぜんと表わされていたにすぎないが, これを各塩の蒸気圧に関する分子降下という形で定量的に表現することができた. 希薄な水溶液においては蒸気圧降下は溶質の種類に関係なく濃度により定まるが, 飽和溶液においては各塩に特有な蒸気圧降下作用, すなわち分子降下がある. これはイオンの水和現象に関する考察により解釈することができる.
(5) 食塩の表面は食塩を液底体の一部とする食塩と不純分との混合飽和溶液の薄膜で覆われていると見なされるので, 本報の理論により食塩表面の呈する蒸気圧, 吸放湿速度等は不純分組成と水分から求められ, また外囲の湿度変化に応じた食塩の溶解析出量および吸放湿量等を不純分組成から算出することもできる.
本報の理論は食塩以外の無機塩類の結晶に対しても適用できることは明らかである. 本報の理論による固結現象の定量的解析は続報において行なう予定である.

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