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In Situ Direct Measurement of Vapor Pressures and Thermodynamic Parameters of Volatile Organic Materials in the Vapor Phase: Benzoic Acid, Ferrocene, and Naphthalene
Author(s) -
Hikal Walid M.,
Weeks Brandon L.
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300182
Subject(s) - vapor pressure , benzoic acid , sublimation (psychology) , chemistry , ferrocene , naphthalene , analytical chemistry (journal) , atmospheric temperature range , enthalpy of sublimation , thermodynamics , inorganic chemistry , organic chemistry , psychology , physics , electrode , electrochemistry , psychotherapist
We report the direct determination of vapor pressures and optical and thermodynamic parameters of powders of low‐volatile materials in their vapor phase using a commercial UV/Vis spectrometer. This methodology is based on the linear proportionality between the density of the saturated gas of the material and the absorbance of the gas at different temperatures. The vapor pressure values determined for benzoic acid and ferrocene are in good agreement with those reported in the literature with ∼2–7 % uncertainty. Thermodynamic parameters of benzoic acid, ferrocene, and naphthalene are determined in situ at temperatures below their melting points. The sublimation enthalpies of the investigated organic molecules are in excellent agreement with the ICTAC recommended values (less than 1 % difference). This method has been used to measure vapor pressures and thermodynamic parameters of organic volatile materials with vapor pressures of ∼0.5–355 Pa in the 50–100 °C temperature range.