Abstract
The author made a study on relations between the deposition conditions of calcium carbonate and its crystal modifications thereunder. In this study, carbonate ion was introduced electrodialytically into the concentrating compartment and reacted with calcium ionin the solution of the compartment. The rate of deposition was as large as about 0.6-10g/liter·hr Al (OH) 3 was used as an intemal standard of the X-ray diffraction analysis of the crystal modification.
Results obtained were as follows:
1. The Al (OH)3 used as the internal standard for the quantitative analysis of calcite, a ragonite and vaterite proved to be satisfactory.
2. At4-10g/liter·hr in the rate of deposition, calcite was formed even in concentrated sea water or other solutions containing Mg++. The ratio of calcite in CaCO3 showed an increase at higher temperature and larger rate of deposition, and with smaller content of Mg++.
3. Calcite and vaterite were formed in those solutions containing no Mg++. The ratio of vaterite in CaCO3 increased at larger rate of deposition. Mg++ seemed to restrain the formation of vaterite.
