In the present work we used Isothermal Titration Calorimetry (ITC) to investigate the thermodynamics of the process of complexation of 1,10-diaza-4,7,13,16,21,24 hexaoxabycyclo[8.8.8]hexacosane (cryptand [2.2.2]) by potassium ions in aqueous solution. By changing the pH of the solution it has been possible to trigger the reversible complexation/decomplexation of the cryptand with consecutive in situ experiments, assessing for the first time the use of ITC to monitor the thermodynamics of a bistable system.