Chemistry of soil minerals. Part VIII. Synthesis and properties of fluorhectorites

Abstract

An investigation has been made of synthesis conditions leading to water-swelling lithium fluorhectorites. Other phases which appeared, the yields of which had to be minimised, were α-quartz, lithium metasilicate, and fluoramphibole. When made by sintering reactions at 800° the fluorhectorites had exchange capacities of ca. 90 mequiv. per 100 g.; if prepared at 850° with lithium fluoride melts as flux this capacity was ca. 150 mequiv. per 100 g. The water-swelling phases did not lose their ability to swell even after heating to 800°; at higher temperatures there was significant defluorination of the structure.

Na-, K-, Rb-, Cs-, Ca-, Sr-, and Ba-exchanged forms were prepared from the Li-fluorhectorites, and water isotherms, and swelling were measured on all forms. K-, Rb-, and Cs-modifications were essentially anhydrous; the other forms intercalated water in successive layers, the isotherms showing steps for the first and second layers. Third layers were observed only from the X-ray basal spacings of the wetted water-swelling forms. One- and two-layer complexes gave rational higher orders of the basal X-ray reflections, but not the three-layer complexes. One- and two-layer complexes corresponded with 4 or 8 water molecules per unit cell.

Swelling of the exchanged forms in glycol also occurred to give two layer complexes with Li-, Na-, Ca-, Sr-, and Ba- but not with K-, Rb-, and Cs-exchanged forms. Very clear higher orders of the basal reflection were obtained.