1) By minute micro-analysis, average content of Pb in the sea-water is found to be about 2γ/L.
2) By using ThB as radioactive indicator, the precipitation ratio of Ph salts in this analysis was determined in order to obtain accuracy of analysis value, and the salt effect on the sea-water was examined.
3) Deducing from the fact that Ph does not exist in brine, it was found that, alike Au and Ra, at the salt manufacturing process Ph is transferred into the deposited solid substance, and not into brine.
4) Under various presumption, a new method of determining the age of the ocean by the quantity of U and Pb (206) in the sea-water was proposed.
In conclusion, the writers express their hearty thanks to the Department of Education for bestowing the fund for the scientific research for a part of this research.

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Agitation, Concentration of adding NaOH solution and the velocity of adding NaOH solution are correlate to the growthing of Mg(OH)₂ crystal being the greatest the last and agitating time is no influence.
Considerable great crystal of Mg(OH)₂ is prepared.(See photograph).
Filtration is easy when the volume of the crystal of Mg(OH)₂ which is precipitated from 200c. c. sea water, is less than 16c. c. after 1 hour and the more its volume, the harder the filtration is.
Mg-salt in sea water, is completely removed at its PH 10-11 and the mixing of CaCO₃ in Mg(OH)₂ is prevented by breaking down of Ca(HCO₃)₂.

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A Latin square was used to test the efficiency of different methods of drawing the roller (125kg/m) in order to consolidate the soil foundation of the pool. The key to the treatments is given with the plan.(See Fig. 1)
A =Check.(undrew)
B=Drew once on and once back.
C=Drew twice to the same direction.
D=Drew once a direction.
E=Drew once on and once across.
The effects of roller drawing were measured by the penetration depth with Tamura's failing-type hardness-meter and tested at the 5% level of significance. From the results, it was concluded that the drawing effect was negligible, the variation being just that to be expected in sampling from a homogeneons population.

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