Modeling the solid state reaction CO2 center dot C2H2 -> CO2+C2H2

Crystalline CO2 . C2H2 is metastable with respect to solid CO2 and solid C2 H2. Infrared spectra of the bending regions of the three solids are present ed and it is shown that the solid phase decomposition of CO2 . C2H2 preserv es the integrity of the cryofilm sample. Although the plot of fractional de composition against time is sigmoidal it is not well described by the Avram i equation. It is shown that the kinetics of the transformation are well de scribed by a growth in three dimensions, unimpeded until reactant material is locally exhausted. (C) 1998 Elsevier Science B.V. All rights reserved.