THERMODYNAMICS OF THE CELL - ICAL-BAR-NACL(M)VERTICAL-BAR-AGCL-VERTICAL-BAR-AG) IN (METHANOL PLUS WATER) SOLVENT MIXTURES

The electromotive force E of the cell {NaxHg1-x\NaCl(m)\AgCl\Ag} has b een measured at the temperature 298.15 K as a function of the mole fra ction x of Na metal in amalgams and of the molality m of NaCl in (meth anol + water) solvent mixtures containing up to 0.8 mass fraction of m ethanol, with relative permittivities epsilon greater than or equal to 40. The respective standard electromotive forces E(m)(o) have been de termined, together with the activity coefficients gamma(+/-) of NaCl a s a function of its molality. For interpolation purposes the E(m)(o) v alues can be expressed as a function of the methanol mass fraction w(M ) by the following polynomial, valid for 0 less than or equal to w(M) less than or equal to 0.8: E(m)(o)/V = 2.18126 - 0.092727 . w(M)(1/2) + 0.103039 . w(M) - 0.24716 . w(M)(3/2). These results for standard e. m.f.s. lead to a primary hydration number n(hydr)approximate to 7 for NaCl which is in good agreement with previous results using different methods. (C) 1996 Academic Press Limited