The change of the rate‐controlling processes with temperature in the hydration of anhydrous nedocromil sodium by water vapor

Adsorption of water by anhydrous nedocromil sodium from 20 to 40 °C

“…This suggests that the surface area is of less importance than some other feature in the mechanism, and if diffusion of water molecules into the solid is indeed dominant in controlling the rate of hydration, then the role of the crystal structure must be considered. Freer et al 9 have published the results of a single-crystal analysis of NS trihydrate, from which, in the structure features of sodium zeolites, can be seen in that sodium ions are accommodated within tunnels formed by cage like molecules. Diffusion as an activated process in such a structure is approached through a logarithmic analysis of the data.…”

“…Several possible control mechanisms are described and investigated in a theoretical paper in preparation. 9 Changing control processes are indicated as the graphs change from a sigmoidal curve, to linear, to two linear parts and back to sigmoidal curves as the sample temperature was increased. None of the graphs are included because a clearer view of changing control mechanisms is given in Figure 2, where the sample temperature is plotted against total mass gained after 4 h exposed to the constant water vapor pressure.…”