Hydrothermal Treatment of Fluor-phlogopite.–Hydrothermal Treatment of Agglomerate Mass of Synthetic Mica Crystals to Facilitate Separation of Individual Crystals

Agglomerates of synthetic mica crystals were treated hydrothermally with alkali, acid and salt solutions in order to ease the separation of mica crystals which are bonded together by glassy substance. (1) Among treatments with sodium hydroxide solutions of the concentration from 0.5 to 2 N at 350°C for 24 hr., that with 2n sodium hydroxide facilitated greatly the separation of mica crystals. A small amount of fluor-phlogopite probably changed to hydroxyl-phlogopite and hydroxides were produced by the hydro-thermal treatment. (2) The hydration of fluor-phlogopite and the formation of hydroxide were suppressed by the addition of fluorides in the treating solution. It was found that the presence of 1.5 mol. potassium fluoride per liter of treating solution was effective for the suppression. (3) Among treatments with potassium hydroxide solution in the presence of 2 mol. potassium fluoride per liter solution at 350°C for 24 hr., that with 0.25 N or more concentrated solution of potassium hydroxide was effecti...