The experimental data on the metastable zone width, as determined by the maximum supercooling ΔT_max using the conventional polythermal method, of the following six compounds: keto-1,2,3,4-tetrahydro-6-methylcarbazole (KTMC), L(+)-ascorbic acid (LAA), 3-nitro-1,2,4-triazol-5-one (NTO), potassium tetraborate tetrahydrate (KTB), 1,3-dipalmitoyl-2-oleoylglycerol (POP), and tripalmitoylglycerol (PPP) published in the literature are analyzed using the relations: ln(ΔT_max/T₀) = Φ + βlnR (K. Sangwal, Cryst. Res. Technol., 2009, 44, 231) and (T₀/ΔT_max)² = F(1 − ZlnR) (K. Sangwal, Cryst. Growth Des., 2009, 9, 942). Here Φ, β, F and Z are constants, and T₀ is the saturation temperature of a solute–solvent system. It was found that: (1) for all solute–solvent systems the values of −Φ and ln(F^1/2) depend on saturation temperature T₀ by an Arrhenius-type equation with an activation energy E_sat, (2) the activation energy E_sat for different solute–solvent systems does not show any well-defined relationship with their corresponding enthalpy of dissolution ΔH_s, and (3) the parameters β and Z are relatively insensitive to changes in saturation temperature T₀. Analysis of the results suggests that: (1) the absence of intimate relationship between E_sat and ΔH_s for a system is a consequence of the nature of the processes involved; the value of ΔH_s is associated with solute–solvent interactions, whereas the value of E_sat is connected with the diffusion of species involved in the formation of three-dimensional nuclei, and (2) the values of β and Z for a solute–solvent system are determined by the nature of species diffusing in the solution during its cooling.