Boric acid was adsorbed by ferric hydroxide precipitated by the reaction of ferric chloride with sodium hydroxide. The pH of the solution showed a remarkable effect upon the adsorption, and the optimum range of the pH was 7 to 9. The amount of the boron which was adsorbed by the precipitation showed an increase in proportion to the decrease in temperature and the increase in the amount of the precipitation.
Then, the adsorption of boron in artificial or natural bittern was investigated, and the following results were obtained.
(1) The optimum range of pH was 6 to 7. The amount and the rate of the boron adsorbed were less than those of the boric acid solution. When the mol ratio of the amount of ferric hydroxide to the amount of boron in bittern was approximately 13 at pH 6 and 20°C, the adsorption ratio of boron ranged from 55% to 65%. The relation between the amount of the adsorbed boron and the concentration of the boron agreed with Freundlich's adsorption isotherm.
(2) Some amount of elements contained in bittern was adsorbed or co-precipitated with ferric hydroxide. Magnesium and sulphate ions were somewhat strongly adsorbed and seemed to have formed some complex compounds with ferric hydroxide. Therefore, the bittern from which sulphate is removed can utilized for recovering boron.
The method of adsorption with the use of ferric hydroxide is applicable to the collection of boron from bittern.

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A cell consisting of three chambers was used for conducting this experiment, and each chamber was separated from the others with cation exchange membranes. The solution of calcium chloride was circulated in the chambers on both sides of the cell, while the solution of sodium chloride was filled in the central chamber. After a fixed time, measurement was conducted on the quantity of the calcium ions that transferred from the both-side chambers to the central one through the cation exchange membranes.
As a result, it was recognized that the increase in the concentration of the calcium chloride solution in the both-side chambers or the increase in the sodium chloride solution in the central chamber promoted the transferring rate of calcium ions through the cation exchange membranes. However, the rate was more remarkably affected by the concentration of sodium chloride solution than that of the calcium chloride solution, and it decreased when sodium chloride was added into the solution of calcium chloride.
In addition to the above, the effect of temperature on the transferring rate of calcium ions was also measured.

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The addition of salt generally decreased cohesion as in the case of the addition of water, but remarkably increased the connective force, when the soil was dry. This action of sodium chloride was more prominent than that of any other salts.
When the sample was compressed, sodium chloride considerably decreased not only cohesion but also the angle of internal friction, and in dry state, it remarkably increased the both factors.
In general, moisture content at the maxium bearing point was lower than the optimum moisture content in wet state, and it was higher than the optimum moisture content in dry state. These causes were explained by the characters of cohesion and of the angle of internal friction.
The relation between stress and strain was found similar to that of the test of unconfined compressive strength.

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The quantitative analysis of exchangeable Na⁺ by Puri method was examined. The proposed method was as follow:
Portions of air-dired fine soil weighing 4g. are mixed with 30cc of N-(NH₄)₂CO₃, and is centrifuged after 40min. The supernatant solution is gathered four times, and s evaporated to dryness. The residue, after being dissolved, is titrated with standard acid. This titration value gives the amount of exchageable Na⁺ and K⁺(n).
The soil residue in the centrifugal cylinder is mixed with 30cc of N-KCL, and is centrifuged after 1 hr. The supernatant solution is discarded two times. The residue is again mixed with 30cc of N-(NH₄)₂CO₃. The supernatant solution is gathered and evaporated as described in the foregoing. This titration value gives exchangeable capacity (N). Degree of alkalization is calculated by the following formula:
D. A.=100 n/N
This n value contains a few exchangeable K, but for the purpose of the present investigation it was not considered necessary to determine K⁺ separately.
Some salt treated soils were chosen to measure the D. A. values. The results showed a clear difference in the D. A. values between the treated soils (25-42%) and the untreated soils (3-6%).

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