To prevent the scale formation in the evaporation of sea water or brine, we deviced the method “the addition of crystal seeds”, using the calcium sulfate crystals as seeds.
In this paper, we studied on the identi fication of the water of crystallization of calcium sulfate. Three method were adopted, there are the method by the X-rays diffractometer, by the phase-contrast microscope, and using the heavy liquid media, respecitively.
The results are as follows: X-rays diffractometer was excellent in the point of accuracy and heavy media separation or phase-constrast microscope was simple in handling but was insufficient in the point of quantitative analysis.

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The distributions of the quantity of water falling down from the vertical flow concentrator “Shijoka” were studied. Within the range of experiments (40-240 l/hr), the distribution of falling water has nearly no connection with discharge. As the number of sheets of bamboo-branches was increased, the point of maximum concentration in the volume distribution of falling water gradually moved forward. When three or four sheets of bamboo branches (the angleof inclination 30° or 60°) were used, the maximum point arrived at the front edge of the sheet of bamboo-branches. If a piece of net (width of 10cm.) was stretched over the upper sheet of bamboo branches under the water-supplying ditch, it has an excellent influence on the distribution. Moreover, on the basis of experimental results in case of a sheet of bamboo branches, a method for the volume distribution of water was formulated.

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Because the EDTA (ethylenediamine tetraacetic acid disodium salt) methods in volumetric analysis of magnesium and calcium are apt to take large amount of error, where magnesium contents are very small, and calcium are large comparatively in samples, experiments were made to determine factors that the error was constituted, and its values, and to eliminate its effects. The factors selected in this report were the relations between calcium and magnesium concentrations, sodium chloride contents, indivisual differences and standardization of EDTA solution. For the purpose of the direct method for determining traces of magnesium, Titan Yellow method was studied.
It was found that the chief error in EDTA method depended on bias, and the precision was good, so standardization of EDTA solution should be made carefully by the both magnesium and calcium standard solutions under the proper combination with EBT and murexide, and using a same quantities of indicators in every time. When magnesium contents were below 10mg/100ml, and used EBT, the value of error for magnesium determination under the condition of titration in this report, might be estimated +2% by the contents of NaCl 2.5g/100ml owing to Na⁺-EDTA chelate formation, and more than 2% in negative by the Ca 40mg/100ml, which was caused by the less titration value of calcium than the true value, and in the case of coexisting Na⁺ and Ca⁺⁺ in above contents, the error was affected chiefly by calcium, but this error could be eliminated by the addition of Mg 20mg/100ml. In the range of magnesium contents were more than 20mg/100ml, the value of error might be estimated about ±0.5%, so it may be found EDTA method is applicable to practical use. In calcium determination by the murexide indicator, color change in end point should be judged exactly with great care, and other indicator should be studied. On the Titan Yellow method, the interference of calcium could be reduced to negligible value by measuring in addition the same amount of calcium to the samples and standard solution in excess. In the consequence, the concentration-extinction curve was linear up to 4ppm and could be used practically.

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