Recently, as the producting methods of the common salt are modernized, the quality of the salt is becoming pretty well, but we cannot be satisfied with it. For trial, if we observe each crystal of salt with the microscope in detail, we can find the much mother liquor and impurities in it which disturb the transparency, and the lack of uniformity of the crystal form. For the purpose of the improvement these wrong salt crystals We concentrated the saturated brine adding 0-100 p. p. m. of Mn and 10 p. p. m. of surface active agents and crystalllized the salt and then investigated about the effects that additions act upon the transparency, purity, particle size, including amounts of Mn and colour etc. of the crystals of the salt deposited. Consequently, the next results were obtained.
1) By the laboratory test, the transparent, pure, uniform and solid salt crystals were produced by addition of 100 p. p, m. of Mn with 10 p. p. m. of surface active agents, which were bubble antiform agents of gexitan ester system (so-called B. A. F.).
2) By the practical test, we applied this method to the vacuum evaporation and auto-vapour compression system, and obtained good results by addition of 20 p. p m. of Mn and 10 p. p. m. of B. A.F.

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In the Preuious report (Vol.9. No.1), the authors have reported the results of fndamental experiments, that is, the scale can be prevented by the method of “Addition of crystal seeds”. That method was the use of suspended crystal seeds (calsium sulfate crystals) in the brine in the evaporaters. Crystal seeds act calsium sulfate depositing from the brine and make them grow on these crystal seeds rather than the tubes.
This report, basing on the principle of 1st one, is written on application to present salt evaporating appratus, that of Odawara Salt Eperiment Station and Onahama Factory, Japan Monopoly Corporation. The authors have as we expected obtained same results on applying the fundamental experiments to evaporaters. Here, we can conclude that, the method of addition of crystal seeds is possible to concentrate the brine long time continuously, without scaling in auto-vapour compression system and vacuum system (No.1 evaporater).

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