The following formula expressing the caking tendency of common salt under constant conditions was obtained as the result of the studies on such factors as particle size, moisture, etc. which were left behind.
y=k₂θ^1/2e ^{(k₁t+ν/d) p}-k₂'θ^-1/2e^{- (k₁'t-ν/d) p}
ν=f (σ, ψ, m, x)
y: caking strength
p: pressure
t: temperature
θ: time
d: mean particle size
σ: type of particle size distribution and its range
ψ: shape of crystal containing the meaning of courseness of the crystal surface in micro
m: moisture
x: impurities
k₁: constant, specific to the substance
k'₁, k₂, k'₂: constant

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In my Previous Papers, the results of quantitative analyses conducted on the caking tendency of common salt and the pattern of contacts among crystals were clearly illustrated.
Oh the basis of those results, the mechanism of caking under different moistures was well deduced from the course of solute diffusion by placing a reasonable assumption on the shape of equal surface in supersaturation and so forth.
On the other hand, the mechanism of caking under constant conditions was consistently explained from the change of healing area against each factor by means of the partial differentiation.
In addition, an inclusive discussion was conducted on the caking tendency of common salt.

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In the electrolytic concentration of sodium sulfate solution, when the concentration of original solution was higher than 0.1-N, the current efficiency of concentration indicated nearly 80%. A linear relationship was found between the volume of penetrating solution and the amount of concentration ion.
In the electrolytic concentration of the mixed solution of sodium sulfate and sulfuric acid, an increase in free acid concentration in the original solution caused a decrease in the current efficiency f Na⁺ and SO₄^2- and an increase in that of H⁺. The selective coefficient of concentration (P_H^Na) of Na⁺ against H⁺ was about 0.9, and this value was considerably different from that of permselective coefficient (T_H^Na) in those cation exchange membranes used in this experiment.

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The permanganate method has been used in general for determination of manganese in sea water or marine salt, but this method is not a favorable one because it is interfered by chloride. Therefore, the present study was conducted to solve this fault, and a formaldoxime method proved to be most effective. The formaldoxime method, however, revealed the defect that the quantitative value was fluctuated with the rise of temperature. This is believed to occur due to the fact that formaldoxime is decomposed in natural solution, but it was found that the reagent was stabilized by the room temperature over the pH of 10. The absorbance of manganese-formaldoxime chelate had a tendency of increasing with the increase of pH, but the addition of tartaric acid stabilized the absorbance between the pHs of 10 and 13. The common diverse ions in sea water and marine salt were masked by adding tartaric acid, EDTA and hydroxylamine. Manganese in sea water was completely collected by coprecipitation with ferric hydroxide or magnesium hydroxide, but the coprecipitation of magnesium hydroxide was considered favorable because ferric ion must be separated to prevent from its own interference. It was possible to separate a large quantity of iron with anion exchange column chromatography.
The recommended procedure of determination was as follows: Marine salt: After 5g of marine salt was dissolved in 35ml of 1N hydrochloric acid and boiled for a few minutes, it was neutralized with ammonia water and added 5ml of ammonia-ammonium chloride buffer solution (pH10.8), 2ml of 2M tartaric acid and 2ml of formaldoxime solution. It was standed for about 10 minutes, and then added 2ml of 5% EDTA and 2ml of 10% hydroxylamine and diluted to 50ml. After 10minutes, the absorbance was measured at 450mμ. Sea water: Magnesium hydroxide was prepared by adding carefully 1N sodium hydroxide to 400ml sea water and warmed for a few minutes, and then filtered. After the precipitate was dissolved in 0.5N hydrochloric acid, the same operation was conducted as in marine salt.
As compared with the permanganate method, the time required in this method was reduced to one-third, and the sensitivity was increased 4.5 times as much.

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