Activity coefficients of NaCl in trehalose-water and maltose-water mixtures at 298.15 K

The ionic mean activity coefficients of NaCl in trehalose-water and maltose-water mixtures have been experimentally determined at 298.15 K from emf measurements by electrochemical cell containing ion selective electrodes (ISE): Na-ISE\NaCl (m), sugar (Y%), H2O (100 - Y%)\Cl-ISE The electrolyte molality (m) ranged between 0.01 and 3 mol kg(-1), approximately, and the weight percent (Y%) of sugar in the mixture of solvents between 0, 10, 20, 30 and 40%. The system is considered as an electrolyte in a mixture of solvents and the data have been analysed by using the Debye-Huckel and Pitzer equations. The results obtained with both equations are in quite agreement with each other. The variation of the tit parameter from both equations were studied relative to the change in the dielectric properties of the mixture of solvents. Standard free energy of transference were comparatively discussed in terms of ion-solvent, ion-ion interactions and the hydration of both the electrolyte and the sugar. (C) 2003 Elsevier Science Ltd. All rights reserved.