STUDIES ON ACTIVITY COEFFICIENTS OF o, m, p-XYLENE IN AQUEOUS SALT SOLUTIONS

The solution of o, m, p-xylene in water as well as in the aqueous salt solution was determined at 23 degrees C by spectrophotometer. The activity coefficient (f) of each of the xylenes has also been calculated. The salts used are LiCl, NaCl, KCl, SrCl2, BaCl2, LiBr, NaBr and KBr. The salt concentrations (c(2)) used are 0-1 mol L-1. When longf were ploted vs. c(2) for eight salts, the obtained results are all straight lines. On comparison of the slopes of these 24 lines, the salting-out order is BaCl2>SrCl2>NaCl>KCl>NaBr approximate to LiCl>KBr>LiBr for each of the xylenes. The salt effect constant k(s) can be expressed in terms of the sum of k. and k(=1) . The value of k(s) decreases with the increase of the dipole moment of the xylene molecule. The salting-out constants of these xylenes in eight aqueous salt solutions have been calculated respectively by the formulas of (1) Debye-McAulay, (2) Conway-Desnoyers-Smith, (3) McDevit-Long and (4) modified internal pressure theory. Some assumptions were made for the modified equation of the internal pressure theory. When the distance between ion and nonelectrolysis molecule in acqueous salt solution was calculated, Latimer's radii are used instead of the Pauling's radii of ions. For larger nonelectrolyte molecules, equation of the modified internal pressure theory (i) give results in better agreement with the experiment than those of (1), (2) and (3).