Ceramics-Silikáty 20, (1) 23 - 32 (1976)

The formation of magnesium hydrosilicates was studied on samples prepared from MgO and silicagel in aqueous suspension MgO : SiO₂ = 2 : 1 to 1 : 2) at room temperature and under hydrothermal conditions. At 20 °C all MgO reacts within 60 days when the starting ratio does not exceed 3/2. The initially arising globular formations of Mg(OH)₂ react in the presence of water with silicagel at the points of contact. The magnesium hydrosilicate forms pseudomorphoses after Mg(OH)₂. According to the results of X-ray analysis and thermic analysis the material resembles the natural mineral deweylite, is imperfectly crystallized and its character does not change even after seven years of reacting. When the initial mixtures are treated in the autoclave, the nature of the reaction products depends on the ratio of the starting components. Whereas at an MgO : SiO₂ ratio of 3 : 2 the reaction yields a magnesium hydrosilicate similar to clinochrysotile, a ratio of 1 : 1 produces a substance similar to deweylite. The presence of a small amount of talc is also possible.