We studied the scale formation and its prevention in brine preheaters at the vacuum pan system salt manufacturing factory, using brine concentrated in flow-down salt field. The principal components of scale were found to be calcium carbonate and calcium sulfate, and the mechanism of scale formation, as follows:
The calcium carbonate scale was formed by break-up of the bicarbonate ion in heating and boiling the brine, and the calcium sulfate scale by decrease in solubility with increasing brine temperature. We found that addition of 5-50ppm of sodium hexametaphosphate was effective for scale prevention, which was verified in a plant test.

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The boron contents of sea water, brine and bittern were determind by mannitol method after oxidization with potassium permanganate. The results showed that boron contents in sea water, brine and bittern were from 4.2 to 4.5mg/L, from 7.4 to 39.7mg/L, and from 232 to 276mg/L respectively, which showed that the boron in sea water was concentrated in bittern remarkably. The values of B/Cl×10² in sea water and brine were from 0.022 to 0.026 while the values of B/Mg×10² in sea water, brine and bittern were from 0.30 to 0.38.
The behavior of boron during the evaporation process of sea water and bittern was studied. The results showed that there was no danger of loss of boron by volatilization.

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It has been said that the boron contained in sea water, brine and bittern is absorbed into magnesium hydroxide. So, in this paper, the absorption process was investigated to find effective factors. The experimental results were as follows:
1) The quantity of boron absorbed into magnesium hydroxide in the same addition ratio agreed with Freundlich's absorption isotherm.
2) The substance obtained by the reaction between Mg⁺⁺ and alkali absorbed boron more efficiently than magnesium hydroxide added straight to boron contained solution.
3) when natural sea water, brine and bittern were treated with milk of lime, the pH value had a remarkable effect on the absorption, while the difference in boron contents in sea water, brine and bittern had no such effect.

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With the general method of marine salt analysis, alkaline metal sulfates could not be determined, being covered with mother liquors.
When the sample was washed with ether and ethylalcohol, the sulfates remained in the residue, and could then be detemined in single form or as double salts compounded with alkaline earth metal sulfate.
Then, this method was applied to other substances separated in salt making-common salt, bittern salts, and their byproducts.

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The surface structure and texture of potassium chloride crystals containing an additive were investigated with the aid of optical or electron microscope. These crystals in shape of octahedron were obtained by cooling the supersaturated potassium chloride solution containing a mixture of (NaPO₃) n and MnCl₂ as the additive.
1. A growth pattern is found on the crystal surface, with growth layers spread irregularly. The layer develops from a closed loop originating from a pair of opposite dislocations.
2. On the growth layer, there occur small trigonal hillocks and also grain boundary where the additive is probably present.
3. The dbove-mentioned growth feature in the crystallization varies with such factors, as the supersaturation ratio, the rate of cooling the solution and the quantity of the additive in the solution.

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We have known that atmospheric conditions cause the bridging between salt particles, and that salt crystals cake together when salt is stored in bulk or bagged. The result is particles adhering firmly to each other producing the phenomenon known as caking.
Previously we reported on the conditions which influence the caking of salt such as pressure, temperature, storage condition, particle size and moisture.
In this study we expect to reduce the caking tendency by the addition of a small amount in turn of 240 substances--organic and inorganic--under a certain condition, using previously reported equipment and securing with the use of chemical agents sufficient protecting purpose. The substances used with some success were ferric ammonium citrate (brown), K₄Fe(CN)₆, cationic surface active agents, Cd salts and Pb salts. Especially ferric ammonium citrate was the best among them, having the advantage of being a permitted food additive.

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In our previous report we have recognized that salt caking was inhibited by the addition of such anti-caking agents as potassium ferrocyanide, ammonium ferrocyanide and cadmium salts.
It is necessary for practical purposes to study the general correlation between laboratory results and data under working conditions on the protecting effect of each additional agent.
Hence, specimens of salt containing various ant-caking agents were artificially produced and stored under a certain condition.
After a period of 10 months, caking tests were carried out, and it was recognized that the data corresponded almost exactly with the laboratory results.
We have devised an useful sampler for caked salt which proved to be excellent in efficiency, etc.

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