Ionic interaction of potassium chloride in aqueous solutions from interferometric data

An interferometric method for the study of ionic interactions in diluted so lutions of KCl is presented and a term xi similar to the thermodynamic acti vity coefficient is defined. The ratio of these two coefficients is in a li near dependence on the initial solution concentration. For very diluted sol utions, the xi value depends on the concentration according to a relation a nalogous to the Debye-Huckel limiting law, but, at higher concentration, be tter results have been obtained using a corrected form of it, as the observ ed differences should be attributed to some terms which are function of con centration.