Dehydration and rehydration of magadiite and kenyaite

Dehydration and rehydration characteristics of synthetic magadiite and kenyaite were investigated in the temperature range from R.T. to 1000°C, and also under high vacuum at R.T. Magadiite and kenyaite lost interlayered water in the range of R.T.-600°C accompanied by a decrease in basal spacing. At 80°C-100°C, the 'intermediate' step of dehydration was observed for both compounds with a basal spacing of 14.1 angstrom for magadiite and 18.8 angstrom for kenyaite. Reversible rehydration took place completely after heating up to 250°C. The layered structures decomposed at 550°C for magadiite and at 600°C for kenyaite. Under high vacuum, interlayered water of both compounds was eliminated completely from the interlayer space at 10^-5 Torr for 24 h at R.T. However, reversible rehydration was observed, when the 'collapsed' products were kept in atmospheric air for 24 h.