Refractive indices and isentropic compressibilities of glycylglycine- FeCl2 in aqueous ethanol mixtures

Abstract

The density and refractive index studies have been carried out for glycylglycine-FeCl<inf>2</inf> in aqueous ethanol mixtures at four different temperatures in the range T = (288.15 to 318.15) K. A comparative study of the refractive indices obtained experimentally and those calculated by means of Gladstone-Dale and Lorentz-Lorenz relation has been made. Among them, the Gladstone-Dale equation afforded similar values to those obtained experimentally. Isentropic compressibilities, -<inf>S</inf>, and excess molar isentropic compressibilities, KS,m<inf>E</inf>, were estimated using the Kirkwood model. Using the Redlich-Kister type equations, excess partial molar isentropic compressibilities, KS,i<inf>E</inf>, were also obtained. The observed negative values of KS,2<inf>E</inf> in the water-rich region are due to the structural disorderliness. As infinitely dilute water is hydrogen-bonded to ethanol and glycylglycine, the variation of strength of interaction is not sensed by KS,1<inf>E,?</inf>. © 2010 American Chemical Society.