As a fundamental item for the method “addition of crystal seeds”, having studied the change of Ca concentration during transition of calcium sulfate in the brine, we calculated the velocities of dissolution and crystallisation during transition, moreover researched certain factors which effected to the velocities. Following conclusions were obtained.
(1) With increase of calcium sulfate suspended in the brine, velocity of dissolution has increased, but that of crystallisation has been unchanged. There may be, however, a constant value which does not increase the velocity by more addition.
(2) Concentration of the brine has greatly effected to both velocities by the change of Ca concentration and velocity constant K.
(3) The smaller is particle size, the more rapidly reaction goes, but we can not gain the definite connections between them.
(4) With elevation of temperature, reaction velocity should be increased, but when saturation degree of Ca decreases, velocity has a max. value at a temperature, and decrease at higher or lower temperature than the point.
(5) With increase of stirring velocity, the thickness of diffusion layer δ decreases, therefore K increases, but the latest may not increase more than a constant value.

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(1) The chlorine content and the percentage volume after concentrating have been calculated from the specific gravity of the water at various degree of concentration by the following formulas.
For the 1st part
S₁=0.997968+0.012794.Cl₁...(1)
For the 2nd part
S₂=1.002943+0.011830.Cl₂...(2)
For the 3rd part
S₃=1.011613+0.010865.Cl₃...(3)
For the 1st part
C₁=172.21/(78.16041.S₁-78.00159)...(4)
For the 2nd part
C₂=172.21/(84.53013.S₂-84.77891)...(5)
For the 3rd part
C₃=172.21/(92.03611.Sa-93.10493)...(6)
where S_n=Ihe specific gravity of water
Cl_a=The chlorine content in grams per 100cc of water
C_l=100 Cl_o/Cl_n=The percentage volume after concentrating
Cl_o=The chlorine content of sea water=1.7221g/100cc in table 2.
Estimation has been made within the limits of concentration from the sea water to the water concentrated up to saturation with NaCl. Tabulation is as table 1 and 2.
(2) dC/dS has been calculated from the above formulas (4),(5) and (6), and tabulated in table 3 (Fig. 1). From these results the relation between the specific gravity and the percentage volume after concentrating may be observed.
(3) The point at which sea water becomes saturate with NaCl by concentrating has been estimated as follows S=1.2159, Cl=18.804.

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Ordinary products of basic magnesium carbonate were analysed by X-ray diffractometer and the date on Hanawalt's table was supplied. The crystalline composition of them was always the same one and the lattice constants of this crystal were determined (ortho-rhombic, a=8. 34°,b=8.92A, c=I8.42°). It was found that not only the size of crystallite and the rate of crystallization increased, but also the lattice constant c decreased to 18.42° from I8.68° owing to aging of this micro crystal. And with this result, it is illustrated that the optical indexes of these products were different slightly but the chemical composition was the same.

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