We made a study regarding four different decomposing methods in order to produce potassium carbonate or sulfate.
1. When Engel's salt is agitated in hot water, it is decomposed into basic magnesium and carbonate solution as indicated in the following formula:
4 (KHCO₃·MgCO₃·4H₂O)→2K₂CO₃+3MgCO₃·Mg(OH)₂·3H₂O+CO₂+14H₂O
By concentrating this solution, crystalized potassium carbonate can be obtained. In this case, the yield of potassium amounts to approximately 95%.
2. When Engel's salt is agitated withMagnesium hydroxide in cold water, it is decomposed into magnesium carbonate and potassium carbonate solution.
2(KHCO₃·MgCO₃·4H₂O)+Mg(OH)₂→K₂CO₃+MgCO₃·3H₂O+H₂O
By this method, it requires much time to complete reaction, and in order to increase the purity of crystalized potassium carbonate, the quantity of magnesium hydroxide to be added must be equivalent to that of Engel's salt. In this case, the yield of potassium is 75%.
3. When Engel's salt is calcined, it is decomposed into magnesia and potassium carbonate.
2 (KHCO₃·MgCO₃·4H₂O)→2MgO+K₂CO₃+3CO₂+9H₂O
The solubility of this potassium carbonate against coldwater is so high that when the calcination is extracted by cold water, potassium carbonate can easilybe separated from magnesia. In this case, the yield of potassium amounts to 92%.
4. When the mixture of Engel's salt and magnesium sulfate is agitated in hot water, potassium sulfate solution and basic magnesium carbonatecan be obtained asindicated in the following formula:
8(KHCO₃·MgCO₃·4H₂O)+4MgSO₄→3 (3MgCO₃·Mg(OH)₂·3H₂O)+4K₂SO₄+4CO₂
When this solution is concentrated, crystalized potassium sulfate can be obtained. The yield of potassium in this case amounts to 92%-94%, and magnesium sulfate to be added to Engel's salt must be equivalent Engel's salt in quantity.

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When Engel's salt is heated at the temperature higher than 550°C for 30 minutes, the potassium contained in this double salt completely changes into potassium carbonate, When it is extracted by water, it can be separated from the residue as potassium carbonate solution. In addition, when this solution is concentrated, crystalized potassium carbonate can be obtained. Thls crystal contains 1.5mol of water, but scarecely contains magnesium and other impurities. The yield of potassium thus obtained amounts to 93%. The residue obtained by removing potassium carbonate solution seldom contains potassium. It is not pure magnesium oxide, but it is considered basic magnesium carbonate or a mixture of baslc magnesium carbonate and magnesium oxide.

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It was reported in the previous literatures that molybdenum, vanadium and uranium contained in sea water are concentrated in bittern. Therefore, we conducted the present study for the purpose of gathering these constituents from bittern by adsorption of ferric hydroxide. This paper gives data on adsorption curves obtained by experiments which were conducted to find the relationship between pH and adsorption ratio. Optimum pH of adsorption was 3 to 4 in molybdenum, 3 to 7 in vanadium and above 6 in uranium respectively, but only adsorption pH of uranium changed in case of co-existence with carbonate ion, and it adsorbed with pH 7 to 8 in this case.
In addition, this paper gives data on desorption curves for water extraction from adsorbent obtained by experiments which were conducted to find the relationship between pH and desorption ratio. pH of desorption was above 4 in molybdenum, above 7 in vanadium and below 6 in uranium repectively, as pH becomes the higher, desorption of molybdenum and vanadium becomes more complete. Desorption of uranium was done above pH 9 in case of Co-existence with carbonate ion, These results showed a possibility of seprating molybdenum, vanadium and uranium from each other by application of adsorption and desorption. It was also possible to separate molybdenum from vanadium by application of anion exchange column.
Moreover, the methods of determining vanadium by N-benzoyl-N-phenyl-hydroxylamine and uranium by 1, 2-pyridylazo-2-naphthol were checked and improved, and these methods were applied to bittern and others with good results.

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As reported in the previous paper of the series, it was recognized in our previous studies on the electrolytic concentration of sea water with porous ion exchange membranes, that the results of the concentration were influenced by the amount of brine to be produced.
This paper presents a study of effects of current density on the concentration of brine under the condition that the amount of brine was made constant, and the following results were obtained.
1) The concentration of brine increases in accordance with an increase of the current density.
2) Furthermore, the amount of produced salt increases as the current density increases. However, at a high current density, an anticipated yield of the salt can not be obtained, and therefore the current efficiency apparently decreases.
3) The voltage of cell increases in proportion to the current density, while the amount of electric power increases as the current density increases.
4) From the above results, it is concluded that the utilization of porous membranes for the electrolytic concentration of sea water is not suitable method from the viewpoint of industrial use, because it is difficult to produce brine of high concentration.

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We conducted studies on electrochemical properties of ion exchange membranes made from pulverized chelate resin (Dowex A-1) and polyvinylchloride.
(1) Electricresistance of the membrane was measured by mercury-electrode method, and permeability of calcium ion through the membrane against sodium ion was determined by using the electrodialystic cell with five compartments.
(2) Electric resistance of chelate membranes showed a remarkable increase in the low concentration of calcium chloride solution, and it increased in proportion to the increase of electric resistance of the solution.
(3) In the experiments of electrodialysis, each compartment alternately separated by chelate membranes and anion exchange membranes was filled with the mixed solution of sodium chloride and calcium chloride. Both ion concentrations in the central compartment which was concentrated by electrodialysis were determined, and then the permselectivity was calculated.
(4) Permselectivity of calcium ion against sodium ion was not related to the content of calcium, and its value was approximately constant (i. e. about 1.0). But cation transport number of chelate mebranes was decreased by the presence of calcium ion, and then the cation permeability was decreased.

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We tested the effect of salt on the permeability of compacted granite soil, and obtained the following results.
Soil permeability is decreased remarkably by salt. For example, when the soil is compacted at a given moisture less than optimum moisture content, the degree of its permeability becomes about 1/7 by adding 1.7% salt to dry soil.
The most effective quantity of salt for decreasing the soil permeability is the quantity required to just saturate the soil moisture.

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[in Japanese]

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