Free-Energy Change of Exchange Reactions

The free-energy change of ion-exchange reactions in clays has been determined at different temperate ice with Padegaon and aquagel Ca-form of membranes by measuring the potential difference between two electro­lytes separated by the membrane. The temperature coefficient of E.M.F. is nearly the same for the two membranes, but varies with the activity of the cation pairs. The heat of exchange reactions, \(\Delta\)H calculated by using the Gibbs-Helmholtz equation, varies with the cation pair, but for the name pair iv remains almost constant at the different temperature and activity ranges studied. It is peculiar that .\(\Delta\)H value for K—Na pair is much higher than that of either the Mg—K and Ca—K pairs