Henry’s law constants derived from equilibrium static cell measurements for dilute organic–water mixtures

The relationship of pressure and composition in the Henry’s law regime has been experimentally measured in an equilibrium static cell for a set of binary organic–water mixtures. The solutes range from hydrophilic materials, such as alcohol to extremely hydrophobic components, such as toluene and 1,2-dichloroethane. The goal of this study is to determine the effective concentration range over which Henry’s law reasonably approximates the gas–liquid partitioning. With the goal of obtaining accurate values of Henry’s law constant, several methodologies are critically compared for the aqueous solutes examined experimentally. The apparatus employed can determine gas–liquid partitioning coefficients through a variety of methods including direct phase concentration ratios, equilibrium partitioning in closed systems (EPICS), and application of the coexistence equation for γ∞. Results to date indicate a more complex dP/dx behavior in the dilute region than previously assumed; and Henry’s law constant may not strictly apply to hydrophobic materials until the solute concentration is so low that analytical detection is problematic.