Simultaneous determination of the partial vapor pressures for a binary mixture of ferrocene and benzoic acid using UV/Vis absorbance spectroscopy

Determining the vapor pressure of the individual components within a mixture is extremely challenging. Herein, a commercial UV/Vis absorbance spectrometer is used for the direct and simultaneous determination of the vapor pressures and the enthalpies of sublimation of a binary mixture of benzoic acid and ferrocene. In accordance with the Beer–Lambert law, the total absorbance in a series of overlapping isothermal absorbance spectra, in the temperature range of 323.15–373.15 K, is related to the number of vapor molecules at each temperature relative to their predetermined absorbance cross sections. Each component is assumed to behave as an ideal gas whose partial pressure contributions are approximated from Dalton’s law of partial pressures. All results for the vapor pressures and enthalpies are in good agreement (< 5%) with their respective literature values. Furthermore, the methodology presented allows for a significant reduction in the total experimental collection times relative to other standard techniques as well as being mostly independent of errors associated with sample purity.