6.3
6.4
Antoine equation GudangMovies21 Rebahinxxi LK21
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation. The equation was presented in 1888 by the French engineer Louis Charles Antoine (1825–1897).
The Antoine equation is
log
10
p
=
A
−
B
C
+
T
.
{\displaystyle \log _{10}p=A-{\frac {B}{C+T}}.}
where p is the vapor pressure, T is temperature (in °C or in K according to the value of C) and A, B and C are component-specific constants.
The simplified form with C set to zero:
log
10
p
=
A
−
B
T
{\displaystyle \log _{10}p=A-{\frac {B}{T}}}
is the August equation, after the German physicist Ernst Ferdinand August (1795–1870). The August equation describes a linear relation between the logarithm of the pressure and the reciprocal temp. This assumes a temperature-independent heat of vaporization. The Antoine equation allows an improved, but still inexact description of the change of the heat of vaporization with the temperature.
The Antoine equation can also be transformed in a temperature-explicit form with simple algebraic manipulations:
T
=
B
A
−
log
10
p
−
C
{\displaystyle T={\frac {B}{A-\log _{10}\,p}}-C}
Validity range
Usually, the Antoine equation cannot be used to describe the entire saturated vapour pressure curve from the triple point to the critical point, because it is not flexible enough. Therefore, multiple parameter sets for a single component are commonly used. A low-pressure parameter set is used to describe the vapour pressure curve up to the normal boiling point and the second set of parameters is used for the range from the normal boiling point to the critical point.
Typical deviations of a parameter fit over the entire range (experimental data for Benzene)
Example parameters
= Example calculation
=
The normal boiling point of ethanol is TB = 78.32 °C.
P
=
10
(
8.20417
−
1642.89
78.32
+
230.300
)
=
760.0
mmHg
P
=
10
(
7.68117
−
1332.04
78.32
+
199.200
)
=
761.0
mmHg
{\displaystyle {\begin{aligned}P&=10^{\left(8.20417-{\frac {1642.89}{78.32+230.300}}\right)}=760.0\ {\text{mmHg}}\\P&=10^{\left(7.68117-{\frac {1332.04}{78.32+199.200}}\right)}=761.0\ {\text{mmHg}}\end{aligned}}}
(760 mmHg = 101.325 kPa = 1.000 atm = normal pressure)
This example shows a severe problem caused by using two different sets of coefficients. The described vapor pressure is not continuous—at the normal boiling point the two sets give different results. This causes severe problems for computational techniques which rely on a continuous vapor pressure curve.
Two solutions are possible: The first approach uses a single Antoine parameter set over a larger temperature range and accepts the increased deviation between calculated and real vapor pressures. A variant of this single set approach is using a special parameter set fitted for the examined temperature range. The second solution is switching to another vapor pressure equation with more than three parameters. Commonly used are simple extensions of the Antoine equation (see below) and the equations of DIPPR or Wagner.
Units
The coefficients of Antoine's equation are normally given in mmHg—even today where the SI is recommended and pascals are preferred. The usage of the pre-SI units has only historic reasons and originates directly from Antoine's original publication.
It is however easy to convert the parameters to different pressure and temperature units. For switching from degrees Celsius to kelvin it is sufficient to subtract 273.15 from the C parameter. For switching from millimeters of mercury to pascals it is sufficient to add the common logarithm of the factor between both units to the A parameter:
A
P
a
=
A
m
m
H
g
+
log
10
101325
760
=
A
m
m
H
g
+
2.124903.
{\displaystyle A_{\mathrm {Pa} }=A_{\mathrm {mmHg} }+\log _{10}{\frac {101325}{760}}=A_{\mathrm {mmHg} }+2.124903.}
The parameters for °C and mmHg for ethanol
A, 8.20417
B, 1642.89
C, 230.300
are converted for K and Pa to
A, 10.32907
B, 1642.89
C, −42.85
The first example calculation with TB = 351.47 K becomes
log
10
(
P
)
=
10
.
3291
−
1642
.
89
351
.
47
−
42
.
85
=
5
.
005727378
=
log
10
(
101328
P
a
)
.
{\displaystyle \log _{10}(P)=10{.}3291-{\frac {1642{.}89}{351{.}47-42{.}85}}=5{.}005727378=\log _{10}(101328\ \mathrm {Pa} ).}
A similarly simple transformation can be used if the common logarithm should be exchanged by the natural logarithm. It is sufficient to multiply the A and B parameters by ln(10) = 2.302585.
The example calculation with the converted parameters (for K and Pa):
A, 23.7836
B, 3782.89
C, −42.85
becomes
ln
P
=
23
.
7836
−
3782
.
89
351
.
47
−
42
.
85
=
11
.
52616367
=
ln
(
101332
P
a
)
.
{\displaystyle \ln P=23{.}7836-{\frac {3782{.}89}{351{.}47-42{.}85}}=11{.}52616367=\ln(101332\,\mathrm {Pa} ).}
(The small differences in the results are only caused by the used limited precision of the coefficients).
Extension of the Antoine equations
To overcome the limits of the Antoine equation some simple extension by additional terms are used:
P
=
exp
(
A
+
B
C
+
T
+
D
⋅
T
+
E
⋅
T
2
+
F
⋅
ln
(
T
)
)
P
=
exp
(
A
+
B
C
+
T
+
D
⋅
ln
(
T
)
+
E
⋅
T
F
)
.
{\displaystyle {\begin{aligned}P&=\exp {\left(A+{\frac {B}{C+T}}+D\cdot T+E\cdot T^{2}+F\cdot \ln \left(T\right)\right)}\\P&=\exp \left(A+{\frac {B}{C+T}}+D\cdot \ln \left(T\right)+E\cdot T^{F}\right).\end{aligned}}}
The additional parameters increase the flexibility of the equation and allow the description of the entire vapor pressure curve. The extended equation forms can be reduced to the original form by setting the additional parameters D, E and F to 0.
A further difference is that the extended equations use the e as base for the exponential function and the natural logarithm. This doesn't affect the equation form.
Generalized Antoine Equation with Acentric Factor
Lee developed a modified form of the Antoine equation that allows for calculating vapor pressure across the entire temperature range using the acentric factor (𝜔) of a substance. The fundamental structure of the equation is based on the van der Waals equation and builds upon the findings of Wall and Gutmann et al., who reformulated it into the Antoine equation. The proposed equation demonstrates improved accuracy compared to the Lee–Kesler method.
ln
p
v
,
r
=
ln
27
−
27
/
8
A
(
ω
)
T
r
9.5663
+
B
(
ω
)
T
r
2.0074
+
C
(
ω
)
T
r
1.1206
{\displaystyle \ln p_{v,r}=\ln 27-{\frac {27/8}{A(\omega )T_{r}^{9.5663}+B(\omega )T_{r}^{2.0074}+C(\omega )T_{r}^{1.1206}}}}
where A, B, C are as follows
A
(
ω
)
=
−
0.0966
ω
3
+
0.1717
ω
2
+
0.0280
ω
+
0.0498
B
(
ω
)
=
0.6093
ω
3
−
1.2620
ω
2
+
1.3025
ω
+
0.2817
C
(
ω
)
=
−
0.5127
ω
3
+
1.0903
ω
2
−
1.3305
ω
+
0.6925
{\displaystyle {\begin{aligned}A(\omega )&=-0.0966\omega ^{3}+0.1717\omega ^{2}+0.0280\omega +0.0498\\B(\omega )&=0.6093\omega ^{3}-1.2620\omega ^{2}+1.3025\omega +0.2817\\C(\omega )&=-0.5127\omega ^{3}+1.0903\omega ^{2}-1.3305\omega +0.6925\end{aligned}}}
where ln𝑝ᵥ,ᵣ is the natural logarithm of the reduced vapor pressure, 𝑇ᵣ is the reduced temperature, and 𝜔 is the acentric factor.
NIST Chemistry WebBook
Dortmund Data Bank
Directory of reference books and data banks containing Antoine constants
Several reference books and publications, e. g.
Lange's Handbook of Chemistry, McGraw-Hill Professional
Wichterle I., Linek J., "Antoine Vapor Pressure Constants of Pure Compounds"
Yaws C. L., Yang H.-C., "To Estimate Vapor Pressure Easily. Antoine Coefficients Relate Vapor Pressure to Temperature for Almost 700 Major Organic Compounds", Hydrocarbon Processing, 68(10), Pages 65–68, 1989
See also
Vapour pressure of water
Arden Buck equation
Lee–Kesler method
Goff–Gratch equation
Raoult's law
Thermodynamic activity
References
External links
Gallica, scanned original paper
NIST Chemistry Web Book
Calculation of vapor pressures with the Antoine equation
Kata Kunci Pencarian:
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Antoine equation - Wikipedia
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation .
Antoine Equation - vCalc
Aug 23, 2021 · The Antoine Equation calculator computes the apparent vapor pressure of pure substances based on temperature and coefficients for the substance.
Antoine Equation Coefficient for pure substances - My …
Data table of Antoine constants for calculation of saturation pressure of common pure substances
Antoine Equation Coefficient and Calculator - Engineers Edge
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation.
Antoine Equation - SpringerLink
Dec 26, 2015 · The Antoine equation, which solves this problem for pure components, is due to a French engineer (Louis Charles Antoine, 1825–1897) and was first published in “Annales de Physique et de Chimie” in 1891 (Antoine 1891). Antoine introduced an equation able to predict the vapor pressure of pure liquids (vaporization) and solids (sublimation).
3.7: Estimating Vapour Pressure - Engineering LibreTexts
May 22, 2024 · Estimate the vapour pressure of pure compounds at a given temperature using Antoine’s equation
Antoine Equation Calculator for Vapour Pressure versus …
Jun 26, 2024 · This vapor pressure calculator uses the Antoine equation to calculate the vapor pressure of various chemicals (given in dropdown menu) with predefined Antoine coefficients (A, B, C) and temperature (in degrees Celsius), the calculator displays the vapor pressure in mmHg.
Antoine equation - Knowino - TAU
Jan 13, 2011 · The Antoine equation is a mathematical expression (derived from the Clausius-Clapeyron relation) of the relation between the vapor pressure and the temperature of pure substances. The equation was first proposed by Ch. Antoine, a French researcher, in 1888. The basic form of the equation is:
Antoine equation - Citizendium
Jul 11, 2024 · The Antoine equation is a mathematical expression (derived from the Clausius-Clapeyron equation) of the relation between the vapor pressure and the temperature of pure substances. The equation was first proposed by Ch. Antoine, a French researcher, in 1888. [3]
The constants Antoine are three parameters that appear on an empirical relationship between saturation vapor pressure and temperature for pure substances. They depend on each substance and are assumed to be constant in a certain range of temperatures.
