OSMOTICCOEFFICIENT DATAFOR BENZENE-BENZOIC ACID
483
Osmotic Coefficient Data for the System Benzene-Benzoic Acid at 25"
by Kenneth R. Harris and Peter J. Dunlop Department of Physical and Inorganic Chemistry, Uniuersity of Adelaide, Adelaide, South Australia (Received April 4, 1966)
An apparatus is described for the isopiestic measurement of the osmotic coefficients of organic solutions. Data for the system benzene-benzoic acid are reported. An exact equation relating the association constant of dimerization to the osmotic coefficient and the stoichiometric molality for a binary solution is also derived.
Introduction The purpose of this note is to report osmotic coefficient data for the organic system, benzoic acid in benzene. The activity data of 0-14. H. von Gierke' for the system benzene-diphenyl mas used as an isopiestic reference. His results, expressed as osmotic coefficients (&) at the various molalities (WZR), are arranged in Table I. They were transformed12by the method of least squares, into a polynomial of the form
distinguished by subscripts. If deviations from ideality are attributed to the monomer-dimer equilibrium, a simple relation between the association constant and the experimental data may be derived. After some manipulation one obtainsg?lo
K --
(2dj -
1)2
(3)
where
6
4~
=
1
+ CAimRi 2=1
( m
