The process of sorption of transition metal ions from nitrate solutions onto chelating ion-exchange resins containing amino, phosphonic and aminophosphonic acid groups has been studied with the help of a Calvet microcalorimeter. Direct calorimetric measurements were performed at different degrees of exchange and the enthalpy variations for the system were obtained. In this work it is shown what the Irving-Williams rule holds for amino groups containing AS resin. In the case of phosphonic acid groups containing KRF resin, the Delta H of sorption of the transition metal ions depends on the Cartledge ionic potential.