Synthesis of some aluminium silicates

Abstract

Studies in the system A12034Si02 under hydrothermal conditions where three different starting materials (amorphous alumina-quartz, amorphous silica-kaolinite, quartz-kaolinite) were investigated in "pinched-tube" experiments1 were followed by a redetermination in sealed-tube experiments of the synthesis fields obtained from amorphous silica-kaolinite and quartz-kaolinite.2 A synthesis diagram for the starting material amorphous alumina-quartz has now been redetermined in sealed-tube experiments. ExperimentalThe pressure equipment used is similar to that already described.2 Modifications to the equipment, in the form of stellite test-tube bombs each coupled to a Bourdon pressure gauge and controlled with an Ether transitrol temperature regulator, enabled more effective control to be attained in some of the experiments. Errors in temperature control were within &l% a t all temperatures.Quartz and amorphous (chromatographic) alumina were mixed in the molecular proportions A1203,4SiOz and Aln03,6SiOz. Samples together with water were placed in silver capsules and sealed. Runs commenced with rapid heating periods (e.g. from room temperature to 400' in 20 min) and were terminated with air quenching. Products were examined with a Philips X-ray diffractometer using filtered Cu radiation.