Temperature dependences of limiting activity coefficients and Henry's law constants for N-methylpyrrolidone, pyridine, and piperidine in water

Limiting activity coefficients (γ1∞) of N-methylpyrrolidone (NMP), pyridine, and piperidine in water were measured at several temperatures in the range from 333 K to 373 K. Three experimental techniques, namely Rayleigh distillation, differential distillation, and the method of circulation still, were employed for the purpose. A comprehensive review is further presented of experimental data on the limiting activity coefficients γ1∞, infinite dilution partial molar excess enthalpies (H¯1E,∞), and heat capacities (C¯p,1E,∞) of these aqueous solutes. Additionally, to verify fragmentary literature information, solution heat capacity for NMP was also determined in this work using Picker flow microcalorimeter. For each solute, the compiled data were critically evaluated and together with the data measured in this work correlated with a suitable model equation providing adequate simultaneous description of the equilibrium measurements and the calorimetric information. As a result, a recommended thermodynamically consistent temperature dependence of γ1∞ was established in the range from the melting point to the normal boiling point of water. Analogous recommendations were derived also for the temperature dependence of the Henry's law constants (kH).