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Published on: May 11, 2017
Hydrothermal Preparation of a Gehlenite Hydrate
Abstract:
Hydrothermal treatment of synthetic gehlenite (2CaO.Al2O3.SiO2) or of various mixtures of oxides, hydrates, etc., approximating the composition of gehlenite, at 260 to 650° C, produced a hitherto unreported compound having the composition 2CaO.Al2O3.SiO2.H2O. Other phases, usually hydrogarnet, were always present in small amounts. A natural gehlenite containing Fe2O3 and MgO was partly converted to the same hydrate at 450° C. The compound 2CaO.Al2O3.SiO2.8H2O was converted to a hydrogarnet at 250 °C, but formed 2CaO.Al2O3.SiO2.H2O at 350 °C. The new compound has a body-centered cubic structure, with a0 = 8.83 Å. The index of refraction is 1.628. An x-ray diffraction pattern is given, and some similarities between CaO.Al2O3SiO2.H2O and the ternary compound 4CaO.3Al2O3.3H2O are pointed out.
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