We previously have shown that the uncertainty in the IG reaction enthalpies is very similar to that of the IG reaction free energies, for which we used the standard deviation of the absorption occurring in primary and secondary amine based solutions. The results for the carbamate reversion reaction pK R2 (the negative of the carbamate formation reaction value) for the primary and secondary amines are summarized in Table , and compared with scarcely available experimental determinations at 298.15 K. We remark that the equilibrium constant is composition-independent quantity which may be directly predicted from simulation quantities at infinite dilution. On the other hand, this quantity cannot be directly measured experimentally, but must be obtained indirectly from concentration measurements at finite compositions m * , governed by