The measurement of fugacity and the Henry's law constant for volatile organic compounds containing chromophores

Keith B Lodge, Darlington Danso

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

A new method for the measurement of the fugacity and the Henry's law constant for volatile organic compounds containing chromophores is described; this was tested with benzene, toluene and ethylbenzene distributed between air and water. The steadily flowing vapor phase of fixed composition is prepared with a mass-flow controller and syringe pump, a method that has been used to calibrate the adsorption by fibres in solid phase micro extraction. The vapor phase flows in and out of the headspace above pure water in a 1-cm spectrophotometric cell housed in a temperature-controlled holder in a UV-vis spectrophotometer. The approach to equilibrium, as the chemical is transferred from the vapor to the stirred liquid phase, is monitored by following the absorbance of the liquid phase at a selected wavelength. Calibration leads to the following molar absorption coefficients (±standard errors, units of L mol-1 cm-1) in water at 25 °C; for benzene at 260 nm, 101 ± 1; for toluene at 261 nm, 284 ± 1; and, for ethylbenzene at 257 nm, 253 ± 3. The fugacities are linear with respect to the mole fractions in the water. The resulting Henry's law constants (±standard errors, units of 104 kPa) are comparable to published values; at 25 °C, these are for benzene, 2.22 ± 0.05; for toluene, 3.99 ± 0.04; and for ethylbenzene, 5.14 ± 0.06.

Original languageEnglish (US)
Pages (from-to)74-79
Number of pages6
JournalFluid Phase Equilibria
Volume253
Issue number1
DOIs
StatePublished - Apr 1 2007

Fingerprint

Henry law
Volatile Organic Compounds
volatile organic compounds
Chromophores
Volatile organic compounds
chromophores
Ethylbenzene
Toluene
Benzene
toluene
Water
Vapors
benzene
water
liquid phases
vapor phases
Ultraviolet spectrophotometers
syringes
Syringes
mass flow

Keywords

  • Air
  • Benzene
  • Ethylbenzene
  • Fugacity
  • Henry's law
  • Molar absorption coefficients
  • Toluene
  • VOCs
  • Water

Cite this

The measurement of fugacity and the Henry's law constant for volatile organic compounds containing chromophores. / Lodge, Keith B; Danso, Darlington.

In: Fluid Phase Equilibria, Vol. 253, No. 1, 01.04.2007, p. 74-79.

Research output: Contribution to journalArticle

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