A critical compilation of Henry's law constant temperature dependence relations for organic compounds in dilute aqueous solutions

A comprehensive compilation of published studies reporting directly measure d experimental determinations of Henry's law constant (HLC) temperature dep endence relationships for organic compounds in dilute, non-saline aqueous s olutions under ambient conditions was conducted. From this effort, 55 such studies (covering 204 organic compounds) were identified, critically review ed, summarized and discussed. Of the 204 compounds, 57 were studied in more than one investigation. For the 57 'multi-studied' compounds, relatively g ood agreement (averaging within 20-30%) was found between the results from different investigations. Given such results, a 'consensus' relationship (i .e., an average temperature dependence relation) was generated for each of the multi studied compounds. Overall, considering relations established for 197 of the 204 compounds investigated (the results for the other 7 compoun ds being excluded due to poor correlation coefficients), the average slope of the temperature dependence line was found to correspond to an increase i n HLC values by a factor of 1.88 (i.e., an 88% increase) per 10 degreesC ri se in temperature (thermodynamically equivalent to an average enthalpy of v olatilization of 47 kJ/mole). The associated range found for the temperatur e dependence slope corresponds to an increase in HLC values by a factor ran ging from 1.12 to 3.55 (i.e., a 12-255% increase) per 10 degreesC rise (equ ivalent enthalpy of volatilization range: 8-93 kJ/mole). The wide range of slope values found indicates that serious errors may result if one applies the commonly cited 'rule of thumb' that HLC values double per 10 degreesC r ise in temperature to a specific compound. In light of this finding, when f aced with a lack of data, a prudent course for practitioners to take appear s to be conducting a laboratory study to determine the exact temperature de pendence for the compound(s) of interest. (C) 2001 Elsevier Science Ltd. Al l rights reserved.