SIGNIFICANT DISCREPANCIES BETWEEN VANT-HOFF AND CALORIMETRIC ENTHALPIES .3.

The study of a wide variety of reversible reactions in solution indica tes that the enthalpy, Delta H-vH, which controls the temperature vari ation of the equilibrium constant for a reaction, can seldom, if ever, be taken to be independent of the temperature. It is also found in mo st cases that the values for Delta H-vH, properly evaluated as varying with the temperature, differ significantly from the values for the en thalpy, Delta H-cal determined by direct calorimetry under the same ex perimental conditions. In a continuing search for reactions which show agreement between Delta H-vH and Delta H-cal, we have studied by isot hermal titration calorimetry the reactions of heptylamine with heptano ic acid in dodecane solution and of alpha-cyclodextrin with sodium hep tanoate in aqueous solution.