ABSTRACT
Figure 3 shows the separation enthalpy per mole of intercalant against the interplanar distance of the graphite sheets calculated using equation (4). Each curve represents a particular gallery occupancy by guest G. Thus the lower curve represents the first stage (n = 1) C8G (x = 8), second stage (n = 2) C16G (x = 16), and so on, for all stages C8nG. The middle curve is for stages (n) of com position C12„G and the top curve for C16„G. The interplanar distance of inter calated graphite sheets of the nonplanar or nonlinear fluorometallate salts ranges between 7.5 and 8.5 A. For stages of composition C12nG, which is a common one for fluorometallate anion guests, the separation enthalpy is 30 kJ mol-1 of intercalant, but this decreases to 20 kJ mol-1 when the guest concentration rises to Q nG. Note that these enthalpy changes are insensitive to the layer separation at the values common for fluorometallate guests. Evidently for most fluorometallates the enthalpy change in process 2 is approximately constant.
