Mean activity coefficients of sodium chloride in water-ethanol mixtures were determined from potentiometric data, at 25 °C, using the classic Pitzer model, based on molalities, and the Pitzer-Simonson model, based on molar fractions. The molalities of NaCl-varied from 0.1 mol kg" 1 to near saturation, in mixed solvents with compositions of 5, 10, 15 and 20% (w/w) ethanol. The results obtained from the two models were compared. INTRODUCTIONSince the beginning of the 20 th century, the study of the mean activity coefficients of electrolytes in water-alcohol mixtures has received considerable attention in the literature [l, 2].Most of the work deals with potentiometric data, using methanol and ethanol as second solvents.Nevertheless, for the ternary system sodium chloride+water+ethanol, the reports found in the literature comprise only a few studies [3,4,5 ].In this work, mean activity coefficients were determined from potentiometric data for NaCl in aqueous-alcoholic solvents, with 5, 10, 15 and 20% (w/w) of ethanol. The sodium chloride concentrations varied from 0.1 mol kg" 1 to near saturation and data were collected at 25 °C. For each ethanol content in the solvent, a function describing the variation of the mean activity coefficient with salt molality was obtained using the Pitzer model [6]. A more complex model, based on molar fractions and devised by Pitzer and Simonson [7], was also applied, and both results were compared for this ternary system. EXPERIMENTALThe materials used were analytical grade sodium chloride, Merck, 99.5 %+, dried in an oven for 12 hours, at 110 °C, and ethanol, Pronalab R, 99.8 %+. All solutions were prepared by weight,
They were studied in this work, the properties spectrochemicals of the chlorides hydrated of the samarium and dysprosium and hers complexes with ethyl acetate in solution. They were evaluated the coefficients of the absorption integrated, transition baricenters, bond parameters and oscillator strength, obtained with the aid of a program SIMP2FOSC. The phenomena intrinsic of the no-hypersensitivity it has been evidencing in these systems.
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