Solid solution of CaSO
4·2H
2O and CaSO
3. 1/2H
2O was prepared by the reaction between the mixed solution of Na
2SO
4+Na
2SO
3 (Na
2SO
4 is predominant) and CaCl2 solution as described in the previous paper
2). The amount of SO
32- ions incorporated into CaSO
4·2H
2O crystal ([SO
32-]
inc) was considerably affected by the pH of the reactant solution. That is, [SO
32-]
inc was very small at p1-1=4-4. 5 then steeply increased untill pH becomes 5 and showed maximum amount at pH=6. This phenomenon was similar for any reaction temperature, but the higher temperature, the smaller [SO
32-]
inc.
The metal ions such as Me
+, Sr
2+, Ba
2+ presented in the reactant solution gave no significant effect on the amount of [SO
32-] inc. On the contrary, Mn
2+ increased the amount of [SO
32-]
inc. When K-salts was used instead of Na-salts for the original reactant solution, no difference in the amount of [SO
32-]
inc was indicated. Finally, it was found that incorporation of CaSO
3·1/ 2H
2O into CaSO
4.2H
2O crystals changed the physical properties such as water requirement, setting time and strength of calcined gypsum therefrom.
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