KINETICS AND MECHANISM OF ISOTHERMAL DEHYDRATION OF LIKC4H4O6.H2O SINGLE-CRYSTALS

The kinetics of isothermal dehydration of LiKC4H4O6. H2O single-crystals was investigated in the [001] crystallographic direction under a dynamic vacuum of 6.7 × 10-5 Pa with a quartz crystal microbalance. The removal of H2O molecules may be described by a diffusion equation for a semi-infinite medium. The scanning electron microscope data provide some evidence that the dehydration is not a topochemical reaction. From the experimental data it is concluded that the anhydrous product is in the state of ″premelting″. This explains the anomalous diffusion energy ED = 37 ± 1 kcal mol-1 and preexponential factor DO = 5 × 109 cm2 s-1.