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Vapour-liquid equilibrium in the butyl alcohol -n-decane system at 85, 100 and 115°C
127
Fluid Phase Equilibria, 74 (1992) 127-132 Elsevier Science Publishers B.V., Amsterdam
Vapour-liquid
equilibrium in the butyl alcohol - n-decane system at 85, 100
and 115 'C S. Bernatova,
J. Linek
and I.
Wichterle*
Institute
of Chemical Process fundamentals, Czechoslovak 162 02 Prague-Suchdol (Czechoslovakia)
Keywords
: vapour-liquid
equilibrium,
density,
butyl
Academy of Sciences,
alcohol,
decane
(Received November 18, 1991; accepted in final form Harch 23, 1992) ABSTRACT Vapour-liquid equilibrium was measured isothermally in the butyl alcohol - decane system at 85, 100, and 115 ‘C. At two lower temperatures the system exhibits azeotropic behaviour. The densities of liquid mixtures were determined at 25 ‘C. The data were correlated usinz the Marnules, Wilson, and NRTL equations within the accuracy of experimental errors.
INTRODUCTION This paper is a contribution to the IUPAC project dealing with vapourliquid equilibria in l-alkanol - n-alkane mixtures. Here the system containing butyl alcohol and decane is experimentally investigated.
EXPERIMENTAL
Materials used Butyl alcohol, puriss. p.a. (better than 99.5 %, Fluka, Switzerland) was rectified on a 30-plate column packed with glass helices. The distillate was permanently stored above molecular sieve 5A. Decane, puriss. (better than 99.5 %, Fluka, Switzerland) was only dried with molecular sieve 5A. Densitiessof pure components at 25.00 OC were determined as 0.80583 and 0.72623 g/cm for butyl alcohol and decane. respectively; for comparison the values found in literature (Riddick iy”L Buns=, 1970; Timmermans, 1950, 1965) are 0.80567-0.80600. and 0.72625 g/cm , respectively.
Vapour-liquid equilibrium determination The vapour-liquid equilibrium was measured using a recirculation still with total volume of liquid mixture of about 150 ml. The temperature was measured with a quartz thermometer, calibrated against a platinum resistance thermometer. The accuracy of temperature measurement is 20.01 K of temperature on the IPTS-90. The pressure in the system was adjusted to the boiling point of the mixture on the isotherm under study and determined indirectly from the boiling point of water in an ebulliometer connected in parallel to the equi‘to
whom correspondence
037%3812/92/$05.00
should
be addressed
0 1992 Elsevier Science Publishers B.V. All rights reserved
128
S. Bematova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
librium still. The details of the apparatus, procedure and calibration can be found elsewhere (Polednova and Wichterle, 1984). The density measurement was used as an analytical method for determination of composition. For this purpose calibrating mixtures were prepared by successive weighing Of pure Components. Then, their densities were determined at 25.00 OC using a DMA 60+602 vibrating-tube densimeter (A. Paar, Austria). The temperature of the densimeter measuring cell was controlled to to.01 K. The densimeter was tested and calibrated by measuring the density of water and cyclohexane of special purity. The accyracy of the density determination is estimated to be better than f2.10-s g/cm .
RESULTS AND DISCUSSION The densities
were
correlated
d =
+ x,M,/d;
where
x
and xn are
are theamolar is the density
the
mole
by the
+ xllxh[Ai
fractions,
masses of alcohol of the mixture.
equation + Aa(x.-x,,)
do and d;
are
+ As(x.-x,$}
the
(a) and hydrocarbon (hl, The adjustable parameters
,
densities,
(1)
M and M
h
respectively4 and d AI, Aa, and A3 were
determined estimated
by means of a maximum likelihood proc$dure with standard deviations as Q = 0.0001 and (P = 0.00001 g/cm .The experimental values and x d corresponding deviations from smoothed data, and evaluated parameters are summarized in Table 1.
TABLE 1 Density
(g/cm31
d
X
0.0 0.1481 0.2322 0.3205 0.3982 0.4754 0.5875 0.6747 0.7622 0.8148 0.8704 0.8949 0.9232 1.0
0.72623 0.73114 0.73468 0.73893 0.74319 0.74799 0.75614 0.76360 0.77234 0.77836 0.78545 0.78884 0.79300 0.80583
mean deviation
of
the
butyl
(x-xc)~105
alcohol
- decane
mixtures
at
(d-dc)x106
8 -8 -5 3 7 -3 -3 4 -3 -4 -0 6
-20 17 10 -5 -11 3 3 -4 2 3 0 -3
4
7
x is mole fraction of butyl alcohol c denotes value calculated from eqn. Aa = -0.465699, A3 = 0.480574
(1)
with
A’;
1.53451
25.00
‘C
S. Bernatova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
129
TABLE 2 Vapour-liquid equilibrium in the butyl alcohol - decane system X
Y
0.0000 0.0608 0.2928 0.4427 0.6287 0.7244 0.8209 0.8685 0.9161 0.9509 0.9706 0.9855 0.9957 1.0000
0.0000 0.6580 0.8034 0.8291 0.8546 0.8709 0.8936 0.9098 0.9542 0.9319 0.9705 0.9847 0.9964 1.0000
0.0000
0.0000
0.0956
0.6925
0.2550 0.4713 0.6163 0.7315 0.8163 0.8694 0.9144 0.9503 0.9702 0.9852 0.9958 1.0000
0.7912 0.8355 0.8571 0.8780 0.8983 0.9160 0.9361 0.9576 0.9726 0.9859 0.9961 1.0000
28.35 39.15 45.14 47.66 49.39 50.55 51.18 51.69 52.00 52.09 52.15 52.15 52.15
0.0000 0.1312 0.2181 0.4938 0.5967 0.7390 0.8106 0.8705 0.9117 0.9500 0.9695 0.9849 0.9956 1.0000
0.0000 0.7155 0.7692 0.8414 0.8576 0.8846 0.9023 0.9218 0.9397 0.9609 0.9744 0.9871 0.9965 1.0000
t = 115.00 Oc 16.89 51.76 -0.0052 62.10 0.0008 78.70 0.0007 82.26 0.0005 86.57 -0.0001 88.53 0.0000 90.12 0.0000 91.18 0.0000 91.74 0.0003 92.14 0.0002 92.34 -0.0002 92.41 -0.0003 92.48
P.kPa
Ax
t = 85.00 'C 5.09 14.08 -0.0016 22.38 0.0010 24.23 -0.0008 25.75 -0.0001 26.41 0.0001 27.02 0.0004 27.29 0.0004 27.52 -0.0094 27.60 0.0102 27.63 -0.0003 27.60 -0.0004 27.59 0.0007 27.58
t=
AY
0.0031 -0.0004 0.0009 -0.0007 -0.0010 -0.0011 -0.0007 0.0165 -0.0153 0.0003 0.0003 0.0006
AP,kPa At,'C
-0.01 0.02 0.02 -0.03 0.04 -0.03 0.02 -0.02 0.01 -0.01 -0.01 0.00 -0.02 0.01 -0.04 0.02 -0.01 0.01 -0.02 0.01 -0.02 0.01 0.00 0.00
100.00 Oc
9.56
-0.0026 0.0067 0.0008 0.0011 0.0000 -0.0001 0.0001 -0.0012 0.0000 -0.0009 0.0002 -0.0009 0.0003 -0.0006 0.0003 -0.0004 0.0001 -0.0001 0.0000 0.0001 -0.0003 0.0003 -0.0002 0.0002
0.0115 0.0041 -0.0003 -0.0015 -0.0009 -0.0007 -0.0008 -0.0006 -0.0004 -0.0002 0.0002 0.0003
-0.05
0.03 -0.04 0.02 0.00 0.00 0.02 -0.01 0.03 -0.01 0.02 -0.01 -0.02 0.01 -0.02 0.01 -0.02 0.01 -0.03 0.01 -0.01 0.00 -0.01 0.00
-0.12 -0.11 -0.11 -0.05 0.08 0.08 0.08 0.11 -0.05 0.00 0.00 -0.02
0.04 0.03 0.02 0.01 -0.01 -0.01 -0.01 -0.02 0.01 0.00 0.00 0.00
A = experimental - calculated (NRTL)
Vapour-liquid equilibria were measured under isothermal conditions over the whole mole fraction range except for lower pressures where smooth boiling of the mixture cannot be realized. The experimental data are summarited in
S. Bematova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
130
Table 2. Azeotropic points determined from the MlTL correlation are as follows: x = 0.9675. P = 27.65 kPa at 85 OC and x = 0.988, P = 52.16 kPa at 100 ‘C. The system exhibits no azeotropic behaviour at 115’C. In the data reduction a maximum likelihood procedure was used as described by Hdla et a1.(1982). A symmetrical objective function was evaluated using standard deviations estimated as Q = u = 0.001, Qp = 0.1 % of experimental value,
u = 0.02 K for phase compositions, pressure and temperature, respectit The real gas phase behaviour was taken into the account; the whole
vely.
Table 3 Calculated virial coefficients pure compounds and mixture
B (cm3/molI and molar volumes V (cm3/molI of
System butyl
85 OC alcohol
decane butyl
alcohol
100 Oc
115 Oc
B V
-1823.7 98.8
-1411.2 100.6
-1130.3 102.5
B V
-3909.2 208.6
-3423.1 212.0
-3027.1 215.5
B
-1477.4
-1324.4
-1194.8
- decane
TABLE4 Parameters of correlation - decane system
equations
D(MargulesI a(WBTLI
and mean deviations
LLx
for
the butyl
AP,kPa
At,?
equation (3rd order) 0.0049 0.0048 0.0026 0.0019 0.0018 0.0018
0.11 0.15 0.20
0.08 0.05 0.03
2.0432 1.7893 1.5325
Margules equation (4th order) 1.8563 0.9577 0.0023 0.0035 1.7369 0.7041 0.0004 0.0010 1.6025 0.4535 0.0007 0.0018
0.02 0.02 0.07
0.02 0.01 0.01
85 100 115
6236.2 5695.3 5173.6
Wilson equation* 896.62 0.0029 918.43 0.0010 916.22 0.0009
0.0035 0.0010 0.0017
0.04 0.05 0.08
0.03 0.02 0.01
85 100 115
1996.2 1905.4 1769.8
NBTLequation* 1742.4 -1.2113 1816.3 -1.1217 1927.8 -0.9618
0.0034 0.0010 0.0018
0.02 0.02 0.07
0.01 0.01 0.01
t,‘C
Aah
85 100 115
1.6927 1.5548 1.3909
Margules 1.6699 1.6087 1.5256
85 100 115
Aha
*parameters Aah, Ah are expressed
0.0021 0.0004 0.0007
AY
in J/m01
alcohol
S. Bematovd et al. /Fluid
131
Phase Equilibria 74 (1992) 127-132
correlation procedure is described elsewhere (Wolfova et al., 19901. The data for both the pure components and mixture are summarized in Table 3. The necessary vapour pressures were evaluated from the Antoine equation: the constants A[kPal, B and C were taken from literature (API. 19701 and are respectively: 6.60170, 1362.39 and 178.770 for butyl alcohol and 6.07857, 1501.268 and 194.480 for decane. However, for the data reduction, constant A for butyl alcohol was adjusted from our experimental vapour pressures of pure component, which is generally recognized and recommended for isothermal data. Adjusted values are 6.60584, 6.60439 and 6.60365 for 85, 100 and 115 'C. respectively. The activity coefficients were fitted both to classical 0largulesl and to non-classical equations (Wilson or NRTL); for their form see Wolfova et a1.(19901. The results of the correlation are summarized in Table 4. It is obvious that mean deviations agree with the estimated standard deviations used in the correlation procedure so confirming its reliability. As an example, the deviations in composition, pressure and temperature corresponding to the
I
I
1
I
P,kR
80
Fig. 1. Pressure - composition diagram for the butyl alcohol - decane system at: 1 - 85 'C; 2 - 100 OC; 3 - 115 C.
132
S. Bernatoua’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
correlation using the NRTL equation are prese ted in Table 2 along with the direct experimental data. The experimental j -y-P data are illustrated in Figure 1. The only data found in literature are those measured by Lee and Scheller (19671 at 100 ‘C. However, these data do not seem to be very good since the vapour pressures of pure butyl alcohol differ cdnsiderably from reliable values. This might be caused by low purity of compounds used for experiments; moreover the spread of data points testify on gross errors. From the correlation of presented data it is obvious that the distribution of deviations from smoothed data confirms there are no large errors. In addition, the data obeying these equations must be thermodynamically consistent.
REFERENCES
API Project 44, 1970. Selected Values of Properties of Hydrocarbons and Related Compounds. Hbla, E., Aim, K., Boublik, T., Linek, J. and Wichterle, I., 1982. Rovnovdha kapalina-para za nizkych a normalnich tlakti. (Vapour-liquid equilibrium at normal and reduced pressures). Academia. Praha. Lee, L. L. and Scheller, W. A., 1967. Isothermal vapor-liquid equilibrium data for the systems heptane-1-propanol at 75 C and decane-l-butanol at 100 C. J. Chem. Eng. Data 12:497-499. Polednova. J. and Wichterle, I., 1984. Vapour-liquid equilibrium in the acetone-water system at 101.325 kPa. Fluid Phase Equilibria 17:115-121. Riddick, J. A. and Bunger, W. B., 1970. Organic Solvents. In: Techniques of Chemistry. Vol.11, Wiley-Interscience, New York. Timmermans, J. , 1950, 1965. Physico-Chemical Constants of Pure Organic Compounds. Vol. I, II., Elsevier. Amsterdam. Wolfova, J., Linek, J. and Wichterle, I., 1990. Vapour-liquid equilibria in the heptane - 3-pentanol and heptane - 2-methyl-2-butanol systems at constant temperature. Fluid Phase Equilibria 54:69-79.
Fluid Phase Equilibria, 74 (1992) 127-132 Elsevier Science Publishers B.V., Amsterdam
Vapour-liquid
equilibrium in the butyl alcohol - n-decane system at 85, 100
and 115 'C S. Bernatova,
J. Linek
and I.
Wichterle*
Institute
of Chemical Process fundamentals, Czechoslovak 162 02 Prague-Suchdol (Czechoslovakia)
Keywords
: vapour-liquid
equilibrium,
density,
butyl
Academy of Sciences,
alcohol,
decane
(Received November 18, 1991; accepted in final form Harch 23, 1992) ABSTRACT Vapour-liquid equilibrium was measured isothermally in the butyl alcohol - decane system at 85, 100, and 115 ‘C. At two lower temperatures the system exhibits azeotropic behaviour. The densities of liquid mixtures were determined at 25 ‘C. The data were correlated usinz the Marnules, Wilson, and NRTL equations within the accuracy of experimental errors.
INTRODUCTION This paper is a contribution to the IUPAC project dealing with vapourliquid equilibria in l-alkanol - n-alkane mixtures. Here the system containing butyl alcohol and decane is experimentally investigated.
EXPERIMENTAL
Materials used Butyl alcohol, puriss. p.a. (better than 99.5 %, Fluka, Switzerland) was rectified on a 30-plate column packed with glass helices. The distillate was permanently stored above molecular sieve 5A. Decane, puriss. (better than 99.5 %, Fluka, Switzerland) was only dried with molecular sieve 5A. Densitiessof pure components at 25.00 OC were determined as 0.80583 and 0.72623 g/cm for butyl alcohol and decane. respectively; for comparison the values found in literature (Riddick iy”L Buns=, 1970; Timmermans, 1950, 1965) are 0.80567-0.80600. and 0.72625 g/cm , respectively.
Vapour-liquid equilibrium determination The vapour-liquid equilibrium was measured using a recirculation still with total volume of liquid mixture of about 150 ml. The temperature was measured with a quartz thermometer, calibrated against a platinum resistance thermometer. The accuracy of temperature measurement is 20.01 K of temperature on the IPTS-90. The pressure in the system was adjusted to the boiling point of the mixture on the isotherm under study and determined indirectly from the boiling point of water in an ebulliometer connected in parallel to the equi‘to
whom correspondence
037%3812/92/$05.00
should
be addressed
0 1992 Elsevier Science Publishers B.V. All rights reserved
128
S. Bematova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
librium still. The details of the apparatus, procedure and calibration can be found elsewhere (Polednova and Wichterle, 1984). The density measurement was used as an analytical method for determination of composition. For this purpose calibrating mixtures were prepared by successive weighing Of pure Components. Then, their densities were determined at 25.00 OC using a DMA 60+602 vibrating-tube densimeter (A. Paar, Austria). The temperature of the densimeter measuring cell was controlled to to.01 K. The densimeter was tested and calibrated by measuring the density of water and cyclohexane of special purity. The accyracy of the density determination is estimated to be better than f2.10-s g/cm .
RESULTS AND DISCUSSION The densities
were
correlated
d =
+ x,M,/d;
where
x
and xn are
are theamolar is the density
the
mole
by the
+ xllxh[Ai
fractions,
masses of alcohol of the mixture.
equation + Aa(x.-x,,)
do and d;
are
+ As(x.-x,$}
the
(a) and hydrocarbon (hl, The adjustable parameters
,
densities,
(1)
M and M
h
respectively4 and d AI, Aa, and A3 were
determined estimated
by means of a maximum likelihood proc$dure with standard deviations as Q = 0.0001 and (P = 0.00001 g/cm .The experimental values and x d corresponding deviations from smoothed data, and evaluated parameters are summarized in Table 1.
TABLE 1 Density
(g/cm31
d
X
0.0 0.1481 0.2322 0.3205 0.3982 0.4754 0.5875 0.6747 0.7622 0.8148 0.8704 0.8949 0.9232 1.0
0.72623 0.73114 0.73468 0.73893 0.74319 0.74799 0.75614 0.76360 0.77234 0.77836 0.78545 0.78884 0.79300 0.80583
mean deviation
of
the
butyl
(x-xc)~105
alcohol
- decane
mixtures
at
(d-dc)x106
8 -8 -5 3 7 -3 -3 4 -3 -4 -0 6
-20 17 10 -5 -11 3 3 -4 2 3 0 -3
4
7
x is mole fraction of butyl alcohol c denotes value calculated from eqn. Aa = -0.465699, A3 = 0.480574
(1)
with
A’;
1.53451
25.00
‘C
S. Bernatova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
129
TABLE 2 Vapour-liquid equilibrium in the butyl alcohol - decane system X
Y
0.0000 0.0608 0.2928 0.4427 0.6287 0.7244 0.8209 0.8685 0.9161 0.9509 0.9706 0.9855 0.9957 1.0000
0.0000 0.6580 0.8034 0.8291 0.8546 0.8709 0.8936 0.9098 0.9542 0.9319 0.9705 0.9847 0.9964 1.0000
0.0000
0.0000
0.0956
0.6925
0.2550 0.4713 0.6163 0.7315 0.8163 0.8694 0.9144 0.9503 0.9702 0.9852 0.9958 1.0000
0.7912 0.8355 0.8571 0.8780 0.8983 0.9160 0.9361 0.9576 0.9726 0.9859 0.9961 1.0000
28.35 39.15 45.14 47.66 49.39 50.55 51.18 51.69 52.00 52.09 52.15 52.15 52.15
0.0000 0.1312 0.2181 0.4938 0.5967 0.7390 0.8106 0.8705 0.9117 0.9500 0.9695 0.9849 0.9956 1.0000
0.0000 0.7155 0.7692 0.8414 0.8576 0.8846 0.9023 0.9218 0.9397 0.9609 0.9744 0.9871 0.9965 1.0000
t = 115.00 Oc 16.89 51.76 -0.0052 62.10 0.0008 78.70 0.0007 82.26 0.0005 86.57 -0.0001 88.53 0.0000 90.12 0.0000 91.18 0.0000 91.74 0.0003 92.14 0.0002 92.34 -0.0002 92.41 -0.0003 92.48
P.kPa
Ax
t = 85.00 'C 5.09 14.08 -0.0016 22.38 0.0010 24.23 -0.0008 25.75 -0.0001 26.41 0.0001 27.02 0.0004 27.29 0.0004 27.52 -0.0094 27.60 0.0102 27.63 -0.0003 27.60 -0.0004 27.59 0.0007 27.58
t=
AY
0.0031 -0.0004 0.0009 -0.0007 -0.0010 -0.0011 -0.0007 0.0165 -0.0153 0.0003 0.0003 0.0006
AP,kPa At,'C
-0.01 0.02 0.02 -0.03 0.04 -0.03 0.02 -0.02 0.01 -0.01 -0.01 0.00 -0.02 0.01 -0.04 0.02 -0.01 0.01 -0.02 0.01 -0.02 0.01 0.00 0.00
100.00 Oc
9.56
-0.0026 0.0067 0.0008 0.0011 0.0000 -0.0001 0.0001 -0.0012 0.0000 -0.0009 0.0002 -0.0009 0.0003 -0.0006 0.0003 -0.0004 0.0001 -0.0001 0.0000 0.0001 -0.0003 0.0003 -0.0002 0.0002
0.0115 0.0041 -0.0003 -0.0015 -0.0009 -0.0007 -0.0008 -0.0006 -0.0004 -0.0002 0.0002 0.0003
-0.05
0.03 -0.04 0.02 0.00 0.00 0.02 -0.01 0.03 -0.01 0.02 -0.01 -0.02 0.01 -0.02 0.01 -0.02 0.01 -0.03 0.01 -0.01 0.00 -0.01 0.00
-0.12 -0.11 -0.11 -0.05 0.08 0.08 0.08 0.11 -0.05 0.00 0.00 -0.02
0.04 0.03 0.02 0.01 -0.01 -0.01 -0.01 -0.02 0.01 0.00 0.00 0.00
A = experimental - calculated (NRTL)
Vapour-liquid equilibria were measured under isothermal conditions over the whole mole fraction range except for lower pressures where smooth boiling of the mixture cannot be realized. The experimental data are summarited in
S. Bematova’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
130
Table 2. Azeotropic points determined from the MlTL correlation are as follows: x = 0.9675. P = 27.65 kPa at 85 OC and x = 0.988, P = 52.16 kPa at 100 ‘C. The system exhibits no azeotropic behaviour at 115’C. In the data reduction a maximum likelihood procedure was used as described by Hdla et a1.(1982). A symmetrical objective function was evaluated using standard deviations estimated as Q = u = 0.001, Qp = 0.1 % of experimental value,
u = 0.02 K for phase compositions, pressure and temperature, respectit The real gas phase behaviour was taken into the account; the whole
vely.
Table 3 Calculated virial coefficients pure compounds and mixture
B (cm3/molI and molar volumes V (cm3/molI of
System butyl
85 OC alcohol
decane butyl
alcohol
100 Oc
115 Oc
B V
-1823.7 98.8
-1411.2 100.6
-1130.3 102.5
B V
-3909.2 208.6
-3423.1 212.0
-3027.1 215.5
B
-1477.4
-1324.4
-1194.8
- decane
TABLE4 Parameters of correlation - decane system
equations
D(MargulesI a(WBTLI
and mean deviations
LLx
for
the butyl
AP,kPa
At,?
equation (3rd order) 0.0049 0.0048 0.0026 0.0019 0.0018 0.0018
0.11 0.15 0.20
0.08 0.05 0.03
2.0432 1.7893 1.5325
Margules equation (4th order) 1.8563 0.9577 0.0023 0.0035 1.7369 0.7041 0.0004 0.0010 1.6025 0.4535 0.0007 0.0018
0.02 0.02 0.07
0.02 0.01 0.01
85 100 115
6236.2 5695.3 5173.6
Wilson equation* 896.62 0.0029 918.43 0.0010 916.22 0.0009
0.0035 0.0010 0.0017
0.04 0.05 0.08
0.03 0.02 0.01
85 100 115
1996.2 1905.4 1769.8
NBTLequation* 1742.4 -1.2113 1816.3 -1.1217 1927.8 -0.9618
0.0034 0.0010 0.0018
0.02 0.02 0.07
0.01 0.01 0.01
t,‘C
Aah
85 100 115
1.6927 1.5548 1.3909
Margules 1.6699 1.6087 1.5256
85 100 115
Aha
*parameters Aah, Ah are expressed
0.0021 0.0004 0.0007
AY
in J/m01
alcohol
S. Bematovd et al. /Fluid
131
Phase Equilibria 74 (1992) 127-132
correlation procedure is described elsewhere (Wolfova et al., 19901. The data for both the pure components and mixture are summarized in Table 3. The necessary vapour pressures were evaluated from the Antoine equation: the constants A[kPal, B and C were taken from literature (API. 19701 and are respectively: 6.60170, 1362.39 and 178.770 for butyl alcohol and 6.07857, 1501.268 and 194.480 for decane. However, for the data reduction, constant A for butyl alcohol was adjusted from our experimental vapour pressures of pure component, which is generally recognized and recommended for isothermal data. Adjusted values are 6.60584, 6.60439 and 6.60365 for 85, 100 and 115 'C. respectively. The activity coefficients were fitted both to classical 0largulesl and to non-classical equations (Wilson or NRTL); for their form see Wolfova et a1.(19901. The results of the correlation are summarized in Table 4. It is obvious that mean deviations agree with the estimated standard deviations used in the correlation procedure so confirming its reliability. As an example, the deviations in composition, pressure and temperature corresponding to the
I
I
1
I
P,kR
80
Fig. 1. Pressure - composition diagram for the butyl alcohol - decane system at: 1 - 85 'C; 2 - 100 OC; 3 - 115 C.
132
S. Bernatoua’ et al. /Fluid Phase Equilibria 74 (1992) 127-132
correlation using the NRTL equation are prese ted in Table 2 along with the direct experimental data. The experimental j -y-P data are illustrated in Figure 1. The only data found in literature are those measured by Lee and Scheller (19671 at 100 ‘C. However, these data do not seem to be very good since the vapour pressures of pure butyl alcohol differ cdnsiderably from reliable values. This might be caused by low purity of compounds used for experiments; moreover the spread of data points testify on gross errors. From the correlation of presented data it is obvious that the distribution of deviations from smoothed data confirms there are no large errors. In addition, the data obeying these equations must be thermodynamically consistent.
REFERENCES
API Project 44, 1970. Selected Values of Properties of Hydrocarbons and Related Compounds. Hbla, E., Aim, K., Boublik, T., Linek, J. and Wichterle, I., 1982. Rovnovdha kapalina-para za nizkych a normalnich tlakti. (Vapour-liquid equilibrium at normal and reduced pressures). Academia. Praha. Lee, L. L. and Scheller, W. A., 1967. Isothermal vapor-liquid equilibrium data for the systems heptane-1-propanol at 75 C and decane-l-butanol at 100 C. J. Chem. Eng. Data 12:497-499. Polednova. J. and Wichterle, I., 1984. Vapour-liquid equilibrium in the acetone-water system at 101.325 kPa. Fluid Phase Equilibria 17:115-121. Riddick, J. A. and Bunger, W. B., 1970. Organic Solvents. In: Techniques of Chemistry. Vol.11, Wiley-Interscience, New York. Timmermans, J. , 1950, 1965. Physico-Chemical Constants of Pure Organic Compounds. Vol. I, II., Elsevier. Amsterdam. Wolfova, J., Linek, J. and Wichterle, I., 1990. Vapour-liquid equilibria in the heptane - 3-pentanol and heptane - 2-methyl-2-butanol systems at constant temperature. Fluid Phase Equilibria 54:69-79.