List of symbolsmole fraction the partial molar enthalpy the relative partial molar enthalpy (eqs 2, 6 and 9) the relative enthalpy of solution (eq. 3) the relative molar enthalpy of solution (eqs. 3 and 4) the relative molar enthalpy of mixing polynomial of the fourth degree parabola directional vector directional vector directional derivative Subscripts 1 = H20 = water 2 = NaC 8 = sodium n-octanoate = sodium caprylate 3 = C10OH = n-decanol k = constant molar ratio of water to sodium octanoate