“…The vapor pressure P L of these substances is in the range of 0.02-1 Pa, and enthalpies of vaporization ∆H vap derived from the slopes m L are in the range of -68 to -82 kJ‚mol -1 . Among a class of structurally related chemicals, P L and ∆H vap decrease with the degree of chlorination, which is consistent with findings for chlorinated phenols (Stephenson and Malanowski, 1987) and chlorinated benzenes (Liu and Dickhut, 1994).…”
The vapor pressures of nine chlorinated catechols, syringols, and syringaldehydes were determined as a function of temperature with a gas chromatographic retention time technique. The vapor pressures at 298.15 K were in the range of 0.02-1 Pa, and the enthalpies of vaporization, between 68 and 82 kJ‚mol -1 . The validity of the technique was established by a calibration involving four chlorinated phenols with well-known vapor pressures. Using these data and previously reported solubility data, Henry's law constants for these substances and some chlorinated guaiacols and veratrols were estimated. The vapor pressure of these substances tends to decrease with increasing polarity and an increasing number of chlorine atoms. Henry's law constants decrease sharply with increasing polarity, suggesting that methylation can result in a significant increase in a chemical's potential for volatilization from water.
“…The vapor pressure P L of these substances is in the range of 0.02-1 Pa, and enthalpies of vaporization ∆H vap derived from the slopes m L are in the range of -68 to -82 kJ‚mol -1 . Among a class of structurally related chemicals, P L and ∆H vap decrease with the degree of chlorination, which is consistent with findings for chlorinated phenols (Stephenson and Malanowski, 1987) and chlorinated benzenes (Liu and Dickhut, 1994).…”
The vapor pressures of nine chlorinated catechols, syringols, and syringaldehydes were determined as a function of temperature with a gas chromatographic retention time technique. The vapor pressures at 298.15 K were in the range of 0.02-1 Pa, and the enthalpies of vaporization, between 68 and 82 kJ‚mol -1 . The validity of the technique was established by a calibration involving four chlorinated phenols with well-known vapor pressures. Using these data and previously reported solubility data, Henry's law constants for these substances and some chlorinated guaiacols and veratrols were estimated. The vapor pressure of these substances tends to decrease with increasing polarity and an increasing number of chlorine atoms. Henry's law constants decrease sharply with increasing polarity, suggesting that methylation can result in a significant increase in a chemical's potential for volatilization from water.
“…The quotient of K OW / K AW was corrected from 25 to 21 °C using the enthalpy of vaporization as described in ref . The enthalpies of vaporization were taken from ref for the PCBs, from ref for the PAHs, and from ref for the chlorobenzenes. 5 Plot of the average soil/air partition coefficient K SA against the quotient of the octanol/water and air/water partition coefficients.…”
Section: Results Of the Methods Validationmentioning
Soil is the primary sink of semivolatile organic compounds
(SOCs) in the terrestrial environment, while the
atmosphere is the primary vector of these substances to
humans via the agricultural food chain. Hence, the
exchange of SOCs between soil and air is of paramount
importance to their environmental fate and potential risk
to humans. In this paper, a method is developed to
determine
soil/air partition coefficients (K
SA) of SOCs.
On the basis
of the solid-phase fugacity meter developed for plants,
the
method was initially tested using a soil contaminated in
the laboratory with chlorinated benzenes, polychlorinated
biphenyls, and polycyclic aromatic hydrocarbons. A
systematic validation exercise demonstrated that the
method
is not subject to a wide range of potential artifacts.
It
was then shown that K
SA in moist soil (relative
humidity =
100%) is independent of the water content of the soil.
The method was then extended to the measurement of
K
SA
in the original soil, which contained background levels
of the SOCs. Good agreement was found between the
K
SA
values measured with the original soil and with the
labora
tory contaminated soil, confirming that the studies with
contaminated soil can be extrapolated to environmental
conditions and demonstrating that it is possible to
directly
measure K
SA at current background levels of soil
contamina
tion. The K
SA values of the compounds
studied ranged
over almost 4 orders of magnitude. There was an
excellent
linear relationship between K
SA and the quotient
of the
octanol/water and air/water partition coefficients
(K
OW/K
AW),
indicating that the Karickhoff model commonly applied
to soil/water partitioning can be extended to the soil/air
system. An equally good regression was obtained
between
K
SA and measured octanol/air partition
coefficients (K
OA).
“…Chemical vapor deposition (CVD) of graphene is carried out using benzene (C 6 H 6 ) (melting point is 278 K; 42 vapor pressure is 130 mbar at 300 K 43 ) supplied through a UHV leak valve connected to a 20 mL UHV-compatible glass tube containing 10 mL of liquid benzene (Sigma-Aldrich). Prior to the deposition, the liquid benzene is purified via the following freeze−pump−thaw cycles.…”
Using
a combination of in situ ultrahigh-vacuum
variable-temperature scanning tunneling microscopy, ex situ Raman spectroscopy, and scanning electron microscopy, we investigated
the growth of graphene using benzene on Pd(111) at temperatures up
to 1100 K. Benzene adsorbs readily on Pd(111) at room temperature
and forms an ordered superstructure upon annealing at 473 K. Exposure
to benzene at 673 K enhances Pd step motion and yields primarily amorphous
carbon upon cooling to room temperature. Monolayer graphene domains,
10–30 nm in size, appear during annealing this sample at 873
K. Dosing benzene at 1100 K results in graphene domains with varying
degrees of crystallinity, while post-deposition annealing at 1100
K for 1200 s yields monolayer graphene domains larger than 150 ×
150 nm2. Our results, which indicate that graphene growth
on Pd(111) using benzene requires deposition/annealing temperatures
higher than 673 K, are in striking contrast with the reported growth
of graphene using benzene at temperatures as low as 373 K on relatively
inert Cu surfaces.
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