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Excess enthalpies of {2-methoxyethanol+methyl 1,1-dimethylethyl ether, orn-heptane} at the temperature 298.15 K
J. Chem. Thermodynamics 1998, 30, 1141]1146 Article No. ct980380
Excess enthalpies of { 2-methoxyethanol H methyl 1,1-dimethylethyl ether, or n-heptane} at the temperature 298.15 K Ding-Yu Peng, a George C. Benson, and Benjamin C.-Y. Lu Department of Chemical Engineering, Uni¨ ersity of Ottowa, Ottawa, Ontario, Canada K1N 6N5
Excess enthalpies have been measured for Ž2-methyoxyethanol q methyl 1,1-methylethyl ether. and for Ž2-methoxyethanol q n-heptane. at the temperature 298.15 K. Smooth representations of the results are described and, in the case of the n-heptane mixture, are used to estimate the limiting mole fractions for the region of partial miscibility. q 1998 Academic Press
KEYWORDS: excess enthalpy; 2-methoxyethanol; methyl 1,1-dimethylethyl ether; n-heptane; partial miscibility
1. Introduction The thermodynamic properties of mixtures containing 2-methoxyethanol Ž2ME. are of interest in view of the wide use of that material as an industrial solvent. The present paper reports excess molar enthalpies, measured at T s 298.15 K, for binary mixtures of 2ME with methyl 1,1-dimethylethyl ether ŽMTBE., or n-heptane ŽnC7.. The measurements for Ž2ME q MTBE. are an extension of our previous studies of mixtures of MTBE with other alkanols Ž1. and ethers.Ž2 ] 6. In the case of Ž2ME q nC7., excess molar enthalpies, measured at more elevated temperatures T s Ž323.15 K, 348.15 K, and 373.15. K4 , have been reported in the literature. Ž7. Our measurements for that mixture were undertaken to study the variation of the excess molar enthalpy at a lower temperature, where partial miscibility occurs.
2. Experimental HPLC Grade 2ME and MTBE, with mole fraction purities exceeding 0.998, were obtained from Sigma-Aldrich. The nC7, pure grade material with mole fraction purity exceeding 0.990, was obtained from the Phillips Chemical Co. Apart from partial degassing, all of the components were used as received from the a Visiting Professor on sabbatical leave from the Department of Chemical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5C9.
0021]9614r98r091141 q 06 $30.00r0
q 1998 Academic Press
1142
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu TABLE 1. Experimental excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4 at the temperature 298.15 K
x 0.0499 0.1002 0.1499 0.2004
HmE a J . moly1
x
128.3 246.5 334.0 401.9
0.2499 0.3000 0.3507 0.3998
HmE a J . moly1
x
449.4 483.8 506.9 518.3
0.4503 0.4988 0.5507 0.5992
HmE a J . moly1
x
521.5 513.7 495.2 477.7
0.6500 0.7013 0.7490 0.8037
HmE a
HmE a
J . moly1
x
J . moly1
447.1 405.9 363.4 302.9
0.8500 0.9000 0.9500
246.8 172.3 90.6
a Representation of HmE by equation Ž1.: HmE rŽJ . moly1 . s x Ž1 y x .2050.45 q 447.24Ž1 y 2 x . q 515.78Ž1 y 2 x . 2 q 78.59Ž1 y 2 x . 3 y 165.83Ž1 y 2 x . 4 4, s s 2.19 J . moly1 .
manufacturers. Densities r ŽT s 298.15 K.rŽkg . my3 ., measured by means of an Anton-Paar densimeter, were 960.11, 735.54, and 679.76 for 2ME, MTBE, and nC7, respectively. These results are in reasonable agreement with values in the literature.Ž8 ] 10. An LKB flow microcalorimeter ŽModel 10700-1., thermostated at ŽT s 298.150 " 0.003. K, was used to measure the excess molar enthalpies HmE . Details of the equipment and the operating procedure have been described previously.Ž11,12. Over most of the mole fraction range, the errors of the excess molar enthalpies and the mole fractions of the mixtures are estimated to be -0.005 . < HmE < and -5 . 10y4 , respectively. However, near the ends of the mole fraction range where the magnitudes of the slopes of the HmE Ž x . curves are large, the error of the results may be ;0.05 . < HmE < .
3. Results and discussion Experimental values of the excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 34 are summarized in table 1. The smoothing function: HmE r Ž J . moly1 . s x Ž 1 y x .
m
Ý
hk Ž 1 y 2 x .
ky 1
,
Ž 1.
ks1
was fitted to these results by the method of least-squares, with all points weighted equally. Values of the coefficients h k are listed in the footnote of table 1, along with the standard deviation s of the representation. The results and their representation by equation Ž1. are plotted in figure 1. The curve is slightly skewed towards x s 0 and has a maximum value of HmE f 520 J . moly1 near x s 0.43. Generally, HmE for mixtures of MTBE with other ethers Ž2 ] 6. is more nearly symmetric about x s 0.5. The present behaviour is reminiscent of that found for MTBE with alkanols.Ž1. For comparison, the curve for ŽMTBE q ethanol. is included in figure 1. xCH 3 OŽCH 2 . 2 OH q Ž1 y The experimental values of HmE for x .CH 3 ŽCH 2 .5 CH 34 are reported in table 2 and plotted in figure 2. The close
HmE of Ž2ME q nC7, or MTBE. at T s 298.15 K
1143
FIGURE 1. Excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4 at the temperature 298.15 K: `, experimental results; }}}, calculated from the representation of the results by equation Ž1.; ] ] ] ], HmE for xCH 3 CH 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4, reference 1.
linearity of the results for mole fractions in the range 0.15 - x - 0.8 can be interpreted as an indication of phase separation. In the analysis of HmE , the results were separated into three sets: L, P, and H, as indicated by the footnotes of the table. L and H consisted of points in the regions of complete miscibility near x s 0 and x s 1, respectively. The third set, P,
1144
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu
FIGURE 2. Excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .CH 3 ŽCH 2 .5 CH 3 4 at the temperature 298.15 K: `, experimental results; I, estimated limits of partial miscibility; }}}, calculated from the representations of the results by equation Ž2..
comprised points in the central region of partial miscibility. Polynomials of the form: HmE r Ž J . moly1 . s
m
Ý
hk Ž z .
ky 1
,
Ž 2.
ks1
where z s x for sets L and P, and z s Ž1 y x . for set H, were determined to
HmE of Ž2ME q nC7, or MTBE. at T s 298.15 K
1145
TABLE 2. Experimental excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .CH 3 ŽCH 2 .5 CH 3 4 at the temperature 298.15 K x 0.0200 a 0.0400 a 0.0400 a 0.0499 a 0.0598 a 0.0598 a 0.0801a 0.0801a 0.1001a
HmE y1
J . mol
219.6 435.2 438.1 518.7 549.7 534.4 607.8 613.5 703.8
x 0.1001a 0.1101a 0.1102 a 0.1514 b 0.2003 b 0.2500 b 0.3000 b 0.3498 b 0.4001b
HmE y1
J . mol
702.2 750.7 745.0 805.9 801.5 792.4 783.1 775.1 767.1
x 0.4507 b 0.5000 b 0.5005 b 0.5502 b 0.5997 b 0.6495 b 0.6997 b 0.7501b 0.8500 c
HmE y1
J . mol
758.2 745.6 748.5 736.5 725.9 715.2 704.1 689.3 643.2
x 0.8600 c 0.8600 c 0.8800 c 0.8801c 0.9000 c 0.9000 c 0.9001c 0.9200 c 0.9200 c
HmE y1
J . mol
627.2 626.7 603.2 602.4 559.9 559.7 559.3 480.6 488.4
HmE
x
J . moly1
0.9400 c 0.9400 c 0.9500 c 0.9500 c 0.9600 c 0.9600 c 0.9800 c 0.9800 c
392.9 392.1 340.2 341.8 270.3 272.9 138.7 142.6
a Set L Žlow x .: HmE rŽJ . moly 1 . s x Ž1.562792 . 10 4 y 1.571926 . 10 5 x q 9.062379 . 10 5 x 2 y 1.937647 . 10 6 x 3 ., s s 20.6 J . moly1 . b Set P Žpartial miscibility.: HmE rŽJ . moly1 . s 841.28 y 193.48 x, s s 3.3 J . moly1 . c Set H Žhigh x .: HmE rŽJ . moly1 . s Ž1 y x .8.67899 . 10 3 y 4.042842 . 10 4 Ž1 y x . q 8.725449 . 10 4 Ž1 y x . 2 y 6.789291 . 10 4 Ž1 y x . 3 4, s s 13.0 J . moly1 .
represent the results in each set. In order to obtain a form suitable for extrapolating the values in sets L and H into the region of partial miscibility, it was necessary to draw reasonable spline fits of the results and to use these in determining the values of the coefficients in equation Ž2.. The resulting representations of HmE and the standard deviations s of the representations are given in the footnotes of the table. The HmE values calculated from equation Ž2. are represented by the solid lines shown in figure 2. The limiting points for phase separation were obtained by solving for the intersections of the pairs ŽL, P. and ŽP, H.. The resulting points x s 0.1309, HmE rŽJ . moly1 . s 816.04 and x s 0.8283, HmE rŽJ . moly1 . s 681.04 are plotted in figure 2. The range Ž0.1309 - x - 0.8283. for the partial miscibility of Ž2ME q nC7. at T s 298.15 K is smaller than the range Ž0.110 - x - 0.874. reportedŽ13. for the partial miscibility of the same mixture at T s 303.15 K. The financial support of the Natural Sciences and Engineering Research Council of Canada ŽNSERC. is gratefully asknowledged. REFERENCES Zhu, S.; Shen, S.; Benson, G. C.; Lu, B. C.-Y. Fluid Phase Equilib. 1994, 94, 217]226. Liao, D.; Tong, Z.; Benson, G. C.; Lu, B. C.-Y. Fluid Phase Equilib. 1997, 131, 133]143. Tong, Z.; Liao, D.; Benson, G. C.; Lu, B. C.-Y. Can. J. Chem. 1997, 75, 308]313. Tong, Z.; Liao, D.; Benson, G. C.; Lu, B. C.-Y. J. Chem. Thermodynamics 1997, 29, 431]439. Tong, Z.; Benson, G. C.; Wang, L. L.; Lu, B. C.-Y. J. Chem. Eng. Data 1996, 41, 865]869. Liao, D.; Tong, Z.; Benson, G. C.; Lu, B. C.-Y. J. Chem. Eng. Data 1997, 42, 531]532. Schulz, W.; Lichtenthaler, R. N. Thermochim. Acta 1989, 151, 261]281. Riddick, J. A.; Bunger, W. B.; Sakano, T. K. Techniques of Chemistry, Vol. II: 4th edition. Weissberger, A.: editor. Wiley: New York. 1986, p. 687. 9. TRC}Thermodynamic Tables}Non-Hydrocarbons. Thermodynamic Research Center: The Texas A & M University System, College Station, TX 77843-3111. 1988, Table 23-2-1-Ž1.2120.-a, dated 30 June 1963.
1. 2. 3. 4. 5. 6. 7. 8.
1146
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu
10. TRC}Thermodynamic Tables}Hydrocarbons. Thermodynamic Research Center: The Texas A & M University System, College Station TX 77843-3111. 1988, Table 23-2-Ž1.101.-a, p. 1, dated 31 October 1977. 11. Tanaka, R.; D’Arcy, P. J.; Benson, G. C. Thermochim. Acta 1975, 11, 163]175. 12. Kimura, F.; Benson, G. C.; Halpin, C. J. Fluid Phase Equilib. 1983, 11, 245]250. 13. Landauer, A.; Lichtenthaler, R. N.; Prausnitz, J. M. J. Chem. Eng. Data 1980, 25, 152]153.
(Recei¨ ed 3 April 1998; in final form 23 April 1998)
WE-122
Excess enthalpies of { 2-methoxyethanol H methyl 1,1-dimethylethyl ether, or n-heptane} at the temperature 298.15 K Ding-Yu Peng, a George C. Benson, and Benjamin C.-Y. Lu Department of Chemical Engineering, Uni¨ ersity of Ottowa, Ottawa, Ontario, Canada K1N 6N5
Excess enthalpies have been measured for Ž2-methyoxyethanol q methyl 1,1-methylethyl ether. and for Ž2-methoxyethanol q n-heptane. at the temperature 298.15 K. Smooth representations of the results are described and, in the case of the n-heptane mixture, are used to estimate the limiting mole fractions for the region of partial miscibility. q 1998 Academic Press
KEYWORDS: excess enthalpy; 2-methoxyethanol; methyl 1,1-dimethylethyl ether; n-heptane; partial miscibility
1. Introduction The thermodynamic properties of mixtures containing 2-methoxyethanol Ž2ME. are of interest in view of the wide use of that material as an industrial solvent. The present paper reports excess molar enthalpies, measured at T s 298.15 K, for binary mixtures of 2ME with methyl 1,1-dimethylethyl ether ŽMTBE., or n-heptane ŽnC7.. The measurements for Ž2ME q MTBE. are an extension of our previous studies of mixtures of MTBE with other alkanols Ž1. and ethers.Ž2 ] 6. In the case of Ž2ME q nC7., excess molar enthalpies, measured at more elevated temperatures T s Ž323.15 K, 348.15 K, and 373.15. K4 , have been reported in the literature. Ž7. Our measurements for that mixture were undertaken to study the variation of the excess molar enthalpy at a lower temperature, where partial miscibility occurs.
2. Experimental HPLC Grade 2ME and MTBE, with mole fraction purities exceeding 0.998, were obtained from Sigma-Aldrich. The nC7, pure grade material with mole fraction purity exceeding 0.990, was obtained from the Phillips Chemical Co. Apart from partial degassing, all of the components were used as received from the a Visiting Professor on sabbatical leave from the Department of Chemical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5C9.
0021]9614r98r091141 q 06 $30.00r0
q 1998 Academic Press
1142
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu TABLE 1. Experimental excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4 at the temperature 298.15 K
x 0.0499 0.1002 0.1499 0.2004
HmE a J . moly1
x
128.3 246.5 334.0 401.9
0.2499 0.3000 0.3507 0.3998
HmE a J . moly1
x
449.4 483.8 506.9 518.3
0.4503 0.4988 0.5507 0.5992
HmE a J . moly1
x
521.5 513.7 495.2 477.7
0.6500 0.7013 0.7490 0.8037
HmE a
HmE a
J . moly1
x
J . moly1
447.1 405.9 363.4 302.9
0.8500 0.9000 0.9500
246.8 172.3 90.6
a Representation of HmE by equation Ž1.: HmE rŽJ . moly1 . s x Ž1 y x .2050.45 q 447.24Ž1 y 2 x . q 515.78Ž1 y 2 x . 2 q 78.59Ž1 y 2 x . 3 y 165.83Ž1 y 2 x . 4 4, s s 2.19 J . moly1 .
manufacturers. Densities r ŽT s 298.15 K.rŽkg . my3 ., measured by means of an Anton-Paar densimeter, were 960.11, 735.54, and 679.76 for 2ME, MTBE, and nC7, respectively. These results are in reasonable agreement with values in the literature.Ž8 ] 10. An LKB flow microcalorimeter ŽModel 10700-1., thermostated at ŽT s 298.150 " 0.003. K, was used to measure the excess molar enthalpies HmE . Details of the equipment and the operating procedure have been described previously.Ž11,12. Over most of the mole fraction range, the errors of the excess molar enthalpies and the mole fractions of the mixtures are estimated to be -0.005 . < HmE < and -5 . 10y4 , respectively. However, near the ends of the mole fraction range where the magnitudes of the slopes of the HmE Ž x . curves are large, the error of the results may be ;0.05 . < HmE < .
3. Results and discussion Experimental values of the excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 34 are summarized in table 1. The smoothing function: HmE r Ž J . moly1 . s x Ž 1 y x .
m
Ý
hk Ž 1 y 2 x .
ky 1
,
Ž 1.
ks1
was fitted to these results by the method of least-squares, with all points weighted equally. Values of the coefficients h k are listed in the footnote of table 1, along with the standard deviation s of the representation. The results and their representation by equation Ž1. are plotted in figure 1. The curve is slightly skewed towards x s 0 and has a maximum value of HmE f 520 J . moly1 near x s 0.43. Generally, HmE for mixtures of MTBE with other ethers Ž2 ] 6. is more nearly symmetric about x s 0.5. The present behaviour is reminiscent of that found for MTBE with alkanols.Ž1. For comparison, the curve for ŽMTBE q ethanol. is included in figure 1. xCH 3 OŽCH 2 . 2 OH q Ž1 y The experimental values of HmE for x .CH 3 ŽCH 2 .5 CH 34 are reported in table 2 and plotted in figure 2. The close
HmE of Ž2ME q nC7, or MTBE. at T s 298.15 K
1143
FIGURE 1. Excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4 at the temperature 298.15 K: `, experimental results; }}}, calculated from the representation of the results by equation Ž1.; ] ] ] ], HmE for xCH 3 CH 2 OH q Ž1 y x .ŽCH 3 . 3 COCH 3 4, reference 1.
linearity of the results for mole fractions in the range 0.15 - x - 0.8 can be interpreted as an indication of phase separation. In the analysis of HmE , the results were separated into three sets: L, P, and H, as indicated by the footnotes of the table. L and H consisted of points in the regions of complete miscibility near x s 0 and x s 1, respectively. The third set, P,
1144
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu
FIGURE 2. Excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .CH 3 ŽCH 2 .5 CH 3 4 at the temperature 298.15 K: `, experimental results; I, estimated limits of partial miscibility; }}}, calculated from the representations of the results by equation Ž2..
comprised points in the central region of partial miscibility. Polynomials of the form: HmE r Ž J . moly1 . s
m
Ý
hk Ž z .
ky 1
,
Ž 2.
ks1
where z s x for sets L and P, and z s Ž1 y x . for set H, were determined to
HmE of Ž2ME q nC7, or MTBE. at T s 298.15 K
1145
TABLE 2. Experimental excess molar enthalpies HmE for xCH 3 OŽCH 2 . 2 OH q Ž1 y x .CH 3 ŽCH 2 .5 CH 3 4 at the temperature 298.15 K x 0.0200 a 0.0400 a 0.0400 a 0.0499 a 0.0598 a 0.0598 a 0.0801a 0.0801a 0.1001a
HmE y1
J . mol
219.6 435.2 438.1 518.7 549.7 534.4 607.8 613.5 703.8
x 0.1001a 0.1101a 0.1102 a 0.1514 b 0.2003 b 0.2500 b 0.3000 b 0.3498 b 0.4001b
HmE y1
J . mol
702.2 750.7 745.0 805.9 801.5 792.4 783.1 775.1 767.1
x 0.4507 b 0.5000 b 0.5005 b 0.5502 b 0.5997 b 0.6495 b 0.6997 b 0.7501b 0.8500 c
HmE y1
J . mol
758.2 745.6 748.5 736.5 725.9 715.2 704.1 689.3 643.2
x 0.8600 c 0.8600 c 0.8800 c 0.8801c 0.9000 c 0.9000 c 0.9001c 0.9200 c 0.9200 c
HmE y1
J . mol
627.2 626.7 603.2 602.4 559.9 559.7 559.3 480.6 488.4
HmE
x
J . moly1
0.9400 c 0.9400 c 0.9500 c 0.9500 c 0.9600 c 0.9600 c 0.9800 c 0.9800 c
392.9 392.1 340.2 341.8 270.3 272.9 138.7 142.6
a Set L Žlow x .: HmE rŽJ . moly 1 . s x Ž1.562792 . 10 4 y 1.571926 . 10 5 x q 9.062379 . 10 5 x 2 y 1.937647 . 10 6 x 3 ., s s 20.6 J . moly1 . b Set P Žpartial miscibility.: HmE rŽJ . moly1 . s 841.28 y 193.48 x, s s 3.3 J . moly1 . c Set H Žhigh x .: HmE rŽJ . moly1 . s Ž1 y x .8.67899 . 10 3 y 4.042842 . 10 4 Ž1 y x . q 8.725449 . 10 4 Ž1 y x . 2 y 6.789291 . 10 4 Ž1 y x . 3 4, s s 13.0 J . moly1 .
represent the results in each set. In order to obtain a form suitable for extrapolating the values in sets L and H into the region of partial miscibility, it was necessary to draw reasonable spline fits of the results and to use these in determining the values of the coefficients in equation Ž2.. The resulting representations of HmE and the standard deviations s of the representations are given in the footnotes of the table. The HmE values calculated from equation Ž2. are represented by the solid lines shown in figure 2. The limiting points for phase separation were obtained by solving for the intersections of the pairs ŽL, P. and ŽP, H.. The resulting points x s 0.1309, HmE rŽJ . moly1 . s 816.04 and x s 0.8283, HmE rŽJ . moly1 . s 681.04 are plotted in figure 2. The range Ž0.1309 - x - 0.8283. for the partial miscibility of Ž2ME q nC7. at T s 298.15 K is smaller than the range Ž0.110 - x - 0.874. reportedŽ13. for the partial miscibility of the same mixture at T s 303.15 K. The financial support of the Natural Sciences and Engineering Research Council of Canada ŽNSERC. is gratefully asknowledged. REFERENCES Zhu, S.; Shen, S.; Benson, G. C.; Lu, B. C.-Y. Fluid Phase Equilib. 1994, 94, 217]226. Liao, D.; Tong, Z.; Benson, G. C.; Lu, B. C.-Y. Fluid Phase Equilib. 1997, 131, 133]143. Tong, Z.; Liao, D.; Benson, G. C.; Lu, B. C.-Y. Can. J. Chem. 1997, 75, 308]313. Tong, Z.; Liao, D.; Benson, G. C.; Lu, B. C.-Y. J. Chem. Thermodynamics 1997, 29, 431]439. Tong, Z.; Benson, G. C.; Wang, L. L.; Lu, B. C.-Y. J. Chem. Eng. Data 1996, 41, 865]869. Liao, D.; Tong, Z.; Benson, G. C.; Lu, B. C.-Y. J. Chem. Eng. Data 1997, 42, 531]532. Schulz, W.; Lichtenthaler, R. N. Thermochim. Acta 1989, 151, 261]281. Riddick, J. A.; Bunger, W. B.; Sakano, T. K. Techniques of Chemistry, Vol. II: 4th edition. Weissberger, A.: editor. Wiley: New York. 1986, p. 687. 9. TRC}Thermodynamic Tables}Non-Hydrocarbons. Thermodynamic Research Center: The Texas A & M University System, College Station, TX 77843-3111. 1988, Table 23-2-1-Ž1.2120.-a, dated 30 June 1963.
1. 2. 3. 4. 5. 6. 7. 8.
1146
D.-Y. Peng, G. C. Benson, and B. C.-Y. Lu
10. TRC}Thermodynamic Tables}Hydrocarbons. Thermodynamic Research Center: The Texas A & M University System, College Station TX 77843-3111. 1988, Table 23-2-Ž1.101.-a, p. 1, dated 31 October 1977. 11. Tanaka, R.; D’Arcy, P. J.; Benson, G. C. Thermochim. Acta 1975, 11, 163]175. 12. Kimura, F.; Benson, G. C.; Halpin, C. J. Fluid Phase Equilib. 1983, 11, 245]250. 13. Landauer, A.; Lichtenthaler, R. N.; Prausnitz, J. M. J. Chem. Eng. Data 1980, 25, 152]153.
(Recei¨ ed 3 April 1998; in final form 23 April 1998)
WE-122