The effect of salt and temperature on the infinite dilution activity coefficients of volatile organic chemicals in water

We have measured the infinite dilution activity coefficients for five volat ile organic compounds (dichloromethane, chloroform, 1,2-dichloroethane, tri chloroethylene and benzene) in aqueous salt solutions over the temperature range of 10 degrees C to 40 degrees C, and sodium chloride concentrations f rom 0 to 2.5 M using headspace gas chromatography. These data were easily f it as a function of salt concentration using the Setschenow expression, and as a function of temperature. By taking derivatives of the fitted data as a function of temperature, one obtains estimates of the partial molar exces s enthalpy and entropy at infinite dilution of the organic chemicals as a f unction of temperature and salt concentration. (C) 1999 Elsevier Science B. V. All rights reserved.