Thermodynamics and Ion Exchange Phenomena

in which HR represents one gram-equivalent of the initial exchanger (i. e., an amount of resin containing Avogadro's number of exchangeable hydrogen ions located at specific sites in the material), NaR represents similarly one gram-equivalent of the sodium form of the resin, and Na+ and H- represent one gram-equivalent of each of the ions in aqueous solution, presumably hydrated. For this process it is possible to determine values of the usual thermodynamic quantities such as AF?, AH, and AS. Of these, AF? is most easily evaluated from experimental measurements of the equilibrium constant, and such evaluation has been the purpose of the majority of the investigations, including that in progress at the University of Kansas. Although a number of other systems have been investigated also, the sodium-hydrogen exchange on Dowex-50 has been studied most exhaustively; data for this system will be used to illustrate the thermodynamic conclusions contained in the latter part of this report.