O p t . , 1960
OSMOTIC -4ND -ACTIVITY COEFFICIENTS OF SULFONIC ACIDS
ture range employed, independent of surface. The reaction is believed, therefore, to proceed by a similar mechanism in all the above cases. Acknowledgment.-This research was supported by a grant from the Petroleum Research Fund, administered by the American Chemical Society.
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Grateful acknowledgment is hereby made t o the donors of said fund. The authors are also indebted to Dr. Raymond R. Sawyer, Mr. Fred Behnke and the Perkin-Elmer Corporation of n'orwalk, Connecticut for the generous loan of long path infrared cells used in the course of this work.
THE EFFECT OF STRUCTURE O S THE OSMOTIC ASD ACTIVITI? COEFFICIENTS OF SOME SULFOXIC ACIDS AKD THEIR SALTS BY 0. D. BONNER'AND 0. C. ROGERS Department of Chemistry, University of South Carolina, Columbia, South Carolina Receaued Apral 16, 1960
Osmotic and activity coefficients are reported for benzenesulfonic and mesitylenesulfonic acids and the lithium and sodium salts of benzenesulfonic, p-ethylbenzenesulfonic, 2,5-dimethylbenzenesnlfonicand mesitylenesulfonic acids a t 25'. These measurements were made by isopiestic comparison of solutions of the sulfonates with sodium chloride solutions as reference standards. The osmotic and activity coefficients of the acids and salts are observed to decrease with increasing molecular weight. The magnitude of the values of these coefficients have the order Li > Xa > H for the higher molecular weight aulfonates, thus indicating that these sulfonic acids are probably only moderatelv strong acids.
Since the introduction of sulfonic acid type of cation-exchange resins which consist of sulfonate exchange sites on polystyrene-divinylbenzene matrices, there have been many attempts to interpret the equilibrium data obtained for exchange reactions involving various pairs of ions. At least two2 of these attempts have iiivolved the use of model compounds similar in structure to the ion exchanges. This work has been handicapped by the scarcity of data for the various aromatic sulfonic acids and their salts. Robinson and Stokes3 have reported osmotic and activity coefficients for the lithium, sodium and potassium salts of p tolucnesulfonic acid while Bonner2b and coworkers have reported data for p-toluenesulfonic, p-ethylbmzenesulfonic, 2,5-dimethylbenzenesulfoiiic, 4,I'-bibenzyldisulfonic and m-benzenedisulfoiiic acids. The only compound for which osmotic and activity coefficient data are available for both the parent acid and some of its salts is therefore p-toluenesulforiic acid. Experimental The various sulfonic acids with the exception of benzenesulfonic acid were prppared by sulfonation of the corresponding purified hydrocarbons. Benzenesulfonic acid was prepared by the hrdrolysis of beiizenesiilfonyl chloride. The sulfonates were rerowred f i orn the sulfuric arid solution by neutralization with potassiiim hydroxide in the case of b m rid :tiid sodium hpdro\ide for the other solulis were then recrystallized at lcwt three times from water or wntrr-methanol solutions and dried to consLant weight. S o structural isomers are possible for any of the sulfonates except the ethylbenzenesulfonates. The purity of the various salts was checked by passing solutions of weighed quantities of each salt through an ion-exchange column in the acid (hydrogen) form and titrating the liberated acid (1) The d a m repoited in this paper are from a project supported by the Vnited States Atomic Energy Commission. (2) (a) G . E. Myera and G. E. Boyd, THISJOURNAL, 60, 521 (1956); (b) 0. D. Bonner, V. E'. Holland and Linda Lou Smith, ibid., 6 0 , 1102
