Measurement of Aqueous Solubility of Hydrophobic Volatile Organic Compounds by Solute Vapor Absorption Technique:  Toluene, Ethylbenzene, Propylbenzene, and Butylbenzene at Temperatures from 273 K to 328 K

An apparatus and procedure are described for measuring the aqueous solubility of hydrophobic volatile compounds. The method employs the solute vapor absorption technique (SVA) for preparation of the saturated solution followed by subsequent off-line HPLC analysis of the cosolvent adjusted aqueous solution. The method circumvents several drawbacks encountered with the traditional liquid−liquid batch contacting (“shake-flask”) system and yields reproducible and precise results (3%). Correct performance of the method was demonstrated using benzene as a test solute. Using the method, aqueous solubilities of lower alkylbenzenes (toluene, ethylbenzene, propylbenzene, and butylbenzene) were determined in the temperature range from 273 K to 328 K. The results are compared with available literature information. An excellent agreement found for toluene gradually deteriorates for higher homologues, with the largest discrepancy occurring at the lowest temperatures. The lack of reliable information for a decisive conclusion at subambient temperatures appears to be rather general, calling for continued experimental effort.