- Email: [email protected]
Isopiestic studies on (methanol + sodium bromide + ammonium bromide) at the temperature 298.15 K: comparison with the partial ideal solution model
J. Chem. Thermodynamics 1998, 30, 709]712 Article No. ct970335
Isopiestic studies on ( methanol H sodium bromide H ammonium bromide) at the temperature 298.15 K: comparison with the partial ideal solution model Zhi-Chang Wang, a Xiu-Yan Li, and Yi-Hui Liu Department of Chemistry, Northeastern Uni¨ ersity, Shenyang 110006, Liaoning, P.R. China Isopiestic measurements have been carried out for the ternary system Žmethanol q sodium bromide q ammonium bromide. at the temperature 298.15 K. The results fit the partial ideal solution model within experimental errors. Q 1998 Academic Press KEYWORDS: isopiestic studies; Žmethanol q sodium bromide q ammonium bromide.; partial ideal solution model
1. Introduction By using the isopiestic technique, accurate activity data have been determined for hundreds of binary and ternary aqueous solutions at the temperature T s 298.15 K.Ž1. Bonner Ž2. has recently extended this technique to binary methanol solutions at T s 298.15 K. Until now, however, the same measurements have not been carried out for any ternary systems involving organic solvents. On the other hand, we have extended the isopiestic technique to binary and ternary alloys,Ž3 ] 5. molten salt mixtures Ž6,7. and slags,Ž8. as well as quaternary aqueous solutions,Ž9 ] 11. and compared the results with a partial ideal solution modelŽ12 ] 16. proposed previously. In this study, we tried to extend this technique to ternary methanol solutions, taking methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 as an example, and to compare the experimental results with the partial ideal solution model.
2. Experimental Isopiestic measurements were made by the method described previously.Ž9 ] 11. Analytical grade NaBr, NH 4 Br, and NaI . 2H 2 O were obtained from Shenyang Chemical Co. and reagent grade methanol was supplied by Tianjin Chemical Co. The reported total amount of solid impurities was mass fraction - 1 . 10y4 for each of the salts. Both NaBr and NH 4 Br were recrystallized from doubly distilled water a
To whom correspondence should be addressed.
0021]9614r98r060709 q 04 $30.00r0
Q 1998 Academic Press
710
Z.-C. Wang, X.-Y. Li, and Y.-H. Liu
and were then dried at low pressure over CaCl 2 , at T s 323 K for NH 4 Br and at T s 423 K for NaBr. The NaI . 2H 2 O was recrystallized from Žwater q acetone. and was dried at T s 333 K under reduced pressure. All the salts were then kept over P2 O5 in a vacuum desiccator before use. Methanol was further purified by repeated distillation, and the middle half of the starting material of each distillation was used. Each sample was run in duplicate and methanolŽA. q sodium iodide4 was used as the reference standard. Preliminary experiments showed that the isopiestic equilibria might be achieved within Ž3 to 5. d. Therefore, the formal equilibrium period was Ž5 to 8. d for each run. At the end of the run, after pressing a lid on to all the cups, the isopiestic apparatus was placed in a dry container where the temperature was kept near to T s 273 K. After opening the isopiestic apparatus, individual caps were immediately placed on the cups before they were weighed. The maxmium difference between duplicates was not larger than 0.5 per cent, and in most cases the difference was not larger than 0.1 per cent. The osmotic coefficient calculated according to Bonner Ž2. was uncertain by about 1 per cent.Ž2.
3. Results and conclusions If m and f denote molality and osmotic coefficient, respectively, and the superscript oo denotes the behaviour for the binary subsystem methanolŽA. q non-volatile soluteŽB.4 , or methanolŽA. q non-volatile soluteŽC.4 , isopiestic behaviour of a ternary methanol solution methanolŽA. q non-volatile soluteŽB. q non-volatile soluteŽC.4 , which obeys the partial ideal solution modelŽ12 ] 16. due to zero interchange energy between B and C, may be expressed as: oo Ž m Brmoo B . q Ž m C rm C . s 1,
Ž 1.
. at constant aA and within 0 F Ž m Crmoo C F 1. In other words, if a ternary system which follows the partial ideal solution model, and two of its binary subsystems are isotonic Žthe solvent activities of all three are equal., then this ternary system has such a composition that it can be prepared by mixing these two binary subsystems. The deviation of a real system from equation Ž1. can then be defined by: oo D s Ž m B rmoo B . q Ž m C rm C . 4 y 1,
Ž 2.
. at constant aA and within 0 F Ž m C rmoo C F 1. Table 1 shows eight sets of isopiestic results for the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system. The first column gives the molality of the reference system methanolŽA. q sodium iodide4 . The second and third columns give the molalities m B of NaBr and m C of NH 4 Br. The fourth column gives the osmotic coefficient of the solutions investigated. The fifth column gives the values of the D function defined by equation Ž2.; it can be seen that < D < F 0.003. According to Rard and Platford,Ž1. an individual isopiestic molality at equilibrium can be determined to "Ž0.0005 . m. to "Ž0.001 . m., and the molality ratio of the reference standard to the test solution determined to Ž"0.001 to "0.002. at T s 298.15 K for aqueous solutions under favorable conditions. However, the precision of the isopiestic experiments for methanol solutions at T s 298.15 K is
ŽMethanol q sodium bromide q ammonium bromide. at T s 298.15 K
711
TABLE 1. Isopiestic results for the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system at T s 298.15 K, where m ref denotes values for the reference system methanolŽA. q sodium iodide4, mo s 1 mol . kgy1 , f denotes osmotic coefficient, and D denotes the experimental deviation from equation Ž1. m refrmo
m B rmo
mC rmo
f
D
1.0002
1.0171 0 0.8336 0.6402 0.4373 0.2230
0 1.1444 0.2086 0.4264 0.6558 0.8919
0.972 0.863 0.948 0.926 0.904 0.886
0.0019 0.0020 0.0030 y0.0014
0.8935 0 0.7342 0.5627 0.3849 0.1967
0 1.0130 0.1833 0.3751 0.5776 0.7873
0.948 0.836 0.923 0.903 0.880 0.861
0.0027 0.0001 0.0010 y0.0027
0.7481 0 0.6125 0.4702 0.3218 0.1659
0 0.8493 0.1533 0.3137 0.4835 0.6620
0.912 0.803 0.891 0.871 0.847 0.824
y0.0008 y0.0021 y0.0006 0.0012
0.5724 0 0.4650 0.3610 0.2470 0.1269
0 0.6538 0.1223 0.2408 0.3707 0.5086
0.873 0.764 0.851 0.830 0.809 0.786
y0.0006 y0.0010 y0.0015 y0.0004
0.5019 0 0.4116 0.3169 0.2173 0.1118
0 0.5751 0.1029 0.2113 0.3260 0.4472
0.858 0.749 0.837 0.815 0.793 0.770
y0.0010 y0.0012 y0.0002 0.0004
0.4741 0 0.3883 0.2979 0.2035 0.1045
0 0.5360 0.0970 0.1986 0.3053 0.4181
0.866 0.766 0.846 0.827 0.807 0.786
0.0000 y0.0011 y0.0012 0.0005
0.4231 0 0.3455 0.2644 0.1798 0.0913
0 0.4682 0.0862 0.1762 0.2695 0.3670
0.880 0.796 0.863 0.845 0.829 0.813
0.0007 0.0012 0.0006 y0.0004
0.3661 0 0.2970 0.2269 0.1536 0.0782
0 0.3971 0.0745 0.1507 0.2303 0.3121
0.896 0.826 0.883 0.869 0.855 0.841
y0.0011 y0.0007 y0.0005 y0.0004
0.8816
0.7345
0.5597
0.4905
0.4697
0.4301
0.3831
712
Z.-C. Wang, X.-Y. Li, and Y.-H. Liu
limited by the relatively high solvent losses, similar to the same measurements for aqueous solutions at high temperature. Thus, the value of < D < F 0.003 would indicate that the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system follows the partial ideal solution model within our experimental errors. It has been shown that the partial ideal solution modelŽ12 ] 16. is valid for the systems solventŽA. q soluteŽB. q soluteŽC. q ??? 4 with zero solute]solute interchange energy. This argument is supported both by the literature data and by our own isopiestic measurements for alloys,Ž4. molten salt mixtures,Ž7. slags,Ž8. non-electrolyte aqueous solutions,Ž9,11. and electrolyte aqueous solutions.Ž10. This paper presents the first evidence for organic solventŽA. q soluteŽB. q soluteŽC. q ??? 4 . We will soon report the isopiestic measurements for Žwater q methanol q sodium bromide q ammonium bromide., where activities of both water and methanol are equal for the quaternary system and its two ternary subsystems Žwater q methanol q sodium bromide. and Žwater q methanol q ammonium bromide.. One of the referees suggested that equation Ž1. is indeed fulfiled quite accurately in, perhaps, up to 3 mol . kgy1 aqueous mixtures with a common ion and, for Žwater q NaCl q CaCl 2 ., it is still fulfiled reasonably well up to 6.7 mol . kgy1 NaCl reference, but a larger deviation is expected when no common ion is present, probably due to the larger interchange energy between the solutes in the latter case. Therefore, further experimental determinations will be very interesting for such organic solventŽA. q soluteŽB. q soluteŽC.4 systems without a common ion, such as methanolŽA. q sodium iodideŽB. q ammonium bromideŽC.4 , to see if a larger deviation from equation Ž1. exists. REFERENCES 1. Rard, J. A.; Platford, R. F. Acti¨ ity Coefficients in Electrolyte Solutions: 2nd edition. Pitzer, K. S.: editor. CRC Press: Boca Raton. 1991, Chap 5. 2. Bonner, O. D. J. Solution Chem. 1987, 16, 307]314. 3. Wang, Z.-C.; Zhang, X.-H.; He, Y.-Z.; Bao, Y.-H. J. Chem. Soc. Faraday Trans. I 1988, 84, 4369]4376. 4. Wang, Z.-C.; Zhang, X.-H.; He, Y.-Z.; Bao, Y.-H. J. Chem. Thermodynamics 1989, 21, 653]665. 5. Wang, Z.-C.; Zhang, X.-H.; Zhou, J.-K. Metall. Trans. B 1992, 23B, 623]629. 6. Wang, Z.-C.; Tian, Y.-W.; Yu, H.-L.; Zhou, J.-K. Metall. Trans. B 1992, 23B, 666]669. 7. Tian, Y.-W.; Yu, H.-L.; Wang, Z.-C.; Zhang, X.-H.; Zhou, J.-K. J. Chem. Thermodynamics 1993, 25, 711]717. 8. Wang, Z.-C.; Tian, Y.-W.; Yu, H.-L.; Zhang, X.-H.; Zhou, J.-K. Metall. Mater. Trans. B 1994, 25B, 103]109. 9. Wang, Z.-C.; Yu, H.-L.; Hu, Y.-F. J. Chem. Thermodynamics 1994, 26, 171]176. 10. Hu, Y.-F.; Wang, Z.-C. J. Chem. Thermodynamics 1994, 26, 429]433. 11. Hu, Y.-F.; Wang, Z.-C. J. Chem. Thermodynamics 1997, 29 879]884. 12. Wang, Z.-C. Acta Metall. Sinica 1980, 16, 195]206. 13. Wang, Z.-C. Acta Metall. Sinica 1981, 17, 168]176. 14. Wang, Z.-C. First China-USA Bilateral Metallurgical Conference. Metall. Ind. Press, The Chinese Society of Metals: Beijing. 1981, pp. 121]136. 15. Wang, Z.-C. Acta Metall. Sinica 1982, 18, 141]152. 16. Wang, Z.-C.; Luck, ¨ R.; Predel, B. J. Chem. Soc. Faraday Trans. 1990, 86, 3641]3646.
(Recei¨ ed 16 September 1997; in final form 9 December 1997)
O-701
Isopiestic studies on ( methanol H sodium bromide H ammonium bromide) at the temperature 298.15 K: comparison with the partial ideal solution model Zhi-Chang Wang, a Xiu-Yan Li, and Yi-Hui Liu Department of Chemistry, Northeastern Uni¨ ersity, Shenyang 110006, Liaoning, P.R. China Isopiestic measurements have been carried out for the ternary system Žmethanol q sodium bromide q ammonium bromide. at the temperature 298.15 K. The results fit the partial ideal solution model within experimental errors. Q 1998 Academic Press KEYWORDS: isopiestic studies; Žmethanol q sodium bromide q ammonium bromide.; partial ideal solution model
1. Introduction By using the isopiestic technique, accurate activity data have been determined for hundreds of binary and ternary aqueous solutions at the temperature T s 298.15 K.Ž1. Bonner Ž2. has recently extended this technique to binary methanol solutions at T s 298.15 K. Until now, however, the same measurements have not been carried out for any ternary systems involving organic solvents. On the other hand, we have extended the isopiestic technique to binary and ternary alloys,Ž3 ] 5. molten salt mixtures Ž6,7. and slags,Ž8. as well as quaternary aqueous solutions,Ž9 ] 11. and compared the results with a partial ideal solution modelŽ12 ] 16. proposed previously. In this study, we tried to extend this technique to ternary methanol solutions, taking methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 as an example, and to compare the experimental results with the partial ideal solution model.
2. Experimental Isopiestic measurements were made by the method described previously.Ž9 ] 11. Analytical grade NaBr, NH 4 Br, and NaI . 2H 2 O were obtained from Shenyang Chemical Co. and reagent grade methanol was supplied by Tianjin Chemical Co. The reported total amount of solid impurities was mass fraction - 1 . 10y4 for each of the salts. Both NaBr and NH 4 Br were recrystallized from doubly distilled water a
To whom correspondence should be addressed.
0021]9614r98r060709 q 04 $30.00r0
Q 1998 Academic Press
710
Z.-C. Wang, X.-Y. Li, and Y.-H. Liu
and were then dried at low pressure over CaCl 2 , at T s 323 K for NH 4 Br and at T s 423 K for NaBr. The NaI . 2H 2 O was recrystallized from Žwater q acetone. and was dried at T s 333 K under reduced pressure. All the salts were then kept over P2 O5 in a vacuum desiccator before use. Methanol was further purified by repeated distillation, and the middle half of the starting material of each distillation was used. Each sample was run in duplicate and methanolŽA. q sodium iodide4 was used as the reference standard. Preliminary experiments showed that the isopiestic equilibria might be achieved within Ž3 to 5. d. Therefore, the formal equilibrium period was Ž5 to 8. d for each run. At the end of the run, after pressing a lid on to all the cups, the isopiestic apparatus was placed in a dry container where the temperature was kept near to T s 273 K. After opening the isopiestic apparatus, individual caps were immediately placed on the cups before they were weighed. The maxmium difference between duplicates was not larger than 0.5 per cent, and in most cases the difference was not larger than 0.1 per cent. The osmotic coefficient calculated according to Bonner Ž2. was uncertain by about 1 per cent.Ž2.
3. Results and conclusions If m and f denote molality and osmotic coefficient, respectively, and the superscript oo denotes the behaviour for the binary subsystem methanolŽA. q non-volatile soluteŽB.4 , or methanolŽA. q non-volatile soluteŽC.4 , isopiestic behaviour of a ternary methanol solution methanolŽA. q non-volatile soluteŽB. q non-volatile soluteŽC.4 , which obeys the partial ideal solution modelŽ12 ] 16. due to zero interchange energy between B and C, may be expressed as: oo Ž m Brmoo B . q Ž m C rm C . s 1,
Ž 1.
. at constant aA and within 0 F Ž m Crmoo C F 1. In other words, if a ternary system which follows the partial ideal solution model, and two of its binary subsystems are isotonic Žthe solvent activities of all three are equal., then this ternary system has such a composition that it can be prepared by mixing these two binary subsystems. The deviation of a real system from equation Ž1. can then be defined by: oo D s Ž m B rmoo B . q Ž m C rm C . 4 y 1,
Ž 2.
. at constant aA and within 0 F Ž m C rmoo C F 1. Table 1 shows eight sets of isopiestic results for the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system. The first column gives the molality of the reference system methanolŽA. q sodium iodide4 . The second and third columns give the molalities m B of NaBr and m C of NH 4 Br. The fourth column gives the osmotic coefficient of the solutions investigated. The fifth column gives the values of the D function defined by equation Ž2.; it can be seen that < D < F 0.003. According to Rard and Platford,Ž1. an individual isopiestic molality at equilibrium can be determined to "Ž0.0005 . m. to "Ž0.001 . m., and the molality ratio of the reference standard to the test solution determined to Ž"0.001 to "0.002. at T s 298.15 K for aqueous solutions under favorable conditions. However, the precision of the isopiestic experiments for methanol solutions at T s 298.15 K is
ŽMethanol q sodium bromide q ammonium bromide. at T s 298.15 K
711
TABLE 1. Isopiestic results for the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system at T s 298.15 K, where m ref denotes values for the reference system methanolŽA. q sodium iodide4, mo s 1 mol . kgy1 , f denotes osmotic coefficient, and D denotes the experimental deviation from equation Ž1. m refrmo
m B rmo
mC rmo
f
D
1.0002
1.0171 0 0.8336 0.6402 0.4373 0.2230
0 1.1444 0.2086 0.4264 0.6558 0.8919
0.972 0.863 0.948 0.926 0.904 0.886
0.0019 0.0020 0.0030 y0.0014
0.8935 0 0.7342 0.5627 0.3849 0.1967
0 1.0130 0.1833 0.3751 0.5776 0.7873
0.948 0.836 0.923 0.903 0.880 0.861
0.0027 0.0001 0.0010 y0.0027
0.7481 0 0.6125 0.4702 0.3218 0.1659
0 0.8493 0.1533 0.3137 0.4835 0.6620
0.912 0.803 0.891 0.871 0.847 0.824
y0.0008 y0.0021 y0.0006 0.0012
0.5724 0 0.4650 0.3610 0.2470 0.1269
0 0.6538 0.1223 0.2408 0.3707 0.5086
0.873 0.764 0.851 0.830 0.809 0.786
y0.0006 y0.0010 y0.0015 y0.0004
0.5019 0 0.4116 0.3169 0.2173 0.1118
0 0.5751 0.1029 0.2113 0.3260 0.4472
0.858 0.749 0.837 0.815 0.793 0.770
y0.0010 y0.0012 y0.0002 0.0004
0.4741 0 0.3883 0.2979 0.2035 0.1045
0 0.5360 0.0970 0.1986 0.3053 0.4181
0.866 0.766 0.846 0.827 0.807 0.786
0.0000 y0.0011 y0.0012 0.0005
0.4231 0 0.3455 0.2644 0.1798 0.0913
0 0.4682 0.0862 0.1762 0.2695 0.3670
0.880 0.796 0.863 0.845 0.829 0.813
0.0007 0.0012 0.0006 y0.0004
0.3661 0 0.2970 0.2269 0.1536 0.0782
0 0.3971 0.0745 0.1507 0.2303 0.3121
0.896 0.826 0.883 0.869 0.855 0.841
y0.0011 y0.0007 y0.0005 y0.0004
0.8816
0.7345
0.5597
0.4905
0.4697
0.4301
0.3831
712
Z.-C. Wang, X.-Y. Li, and Y.-H. Liu
limited by the relatively high solvent losses, similar to the same measurements for aqueous solutions at high temperature. Thus, the value of < D < F 0.003 would indicate that the methanolŽA. q sodium bromideŽB. q ammonium bromideŽC.4 ternary system follows the partial ideal solution model within our experimental errors. It has been shown that the partial ideal solution modelŽ12 ] 16. is valid for the systems solventŽA. q soluteŽB. q soluteŽC. q ??? 4 with zero solute]solute interchange energy. This argument is supported both by the literature data and by our own isopiestic measurements for alloys,Ž4. molten salt mixtures,Ž7. slags,Ž8. non-electrolyte aqueous solutions,Ž9,11. and electrolyte aqueous solutions.Ž10. This paper presents the first evidence for organic solventŽA. q soluteŽB. q soluteŽC. q ??? 4 . We will soon report the isopiestic measurements for Žwater q methanol q sodium bromide q ammonium bromide., where activities of both water and methanol are equal for the quaternary system and its two ternary subsystems Žwater q methanol q sodium bromide. and Žwater q methanol q ammonium bromide.. One of the referees suggested that equation Ž1. is indeed fulfiled quite accurately in, perhaps, up to 3 mol . kgy1 aqueous mixtures with a common ion and, for Žwater q NaCl q CaCl 2 ., it is still fulfiled reasonably well up to 6.7 mol . kgy1 NaCl reference, but a larger deviation is expected when no common ion is present, probably due to the larger interchange energy between the solutes in the latter case. Therefore, further experimental determinations will be very interesting for such organic solventŽA. q soluteŽB. q soluteŽC.4 systems without a common ion, such as methanolŽA. q sodium iodideŽB. q ammonium bromideŽC.4 , to see if a larger deviation from equation Ž1. exists. REFERENCES 1. Rard, J. A.; Platford, R. F. Acti¨ ity Coefficients in Electrolyte Solutions: 2nd edition. Pitzer, K. S.: editor. CRC Press: Boca Raton. 1991, Chap 5. 2. Bonner, O. D. J. Solution Chem. 1987, 16, 307]314. 3. Wang, Z.-C.; Zhang, X.-H.; He, Y.-Z.; Bao, Y.-H. J. Chem. Soc. Faraday Trans. I 1988, 84, 4369]4376. 4. Wang, Z.-C.; Zhang, X.-H.; He, Y.-Z.; Bao, Y.-H. J. Chem. Thermodynamics 1989, 21, 653]665. 5. Wang, Z.-C.; Zhang, X.-H.; Zhou, J.-K. Metall. Trans. B 1992, 23B, 623]629. 6. Wang, Z.-C.; Tian, Y.-W.; Yu, H.-L.; Zhou, J.-K. Metall. Trans. B 1992, 23B, 666]669. 7. Tian, Y.-W.; Yu, H.-L.; Wang, Z.-C.; Zhang, X.-H.; Zhou, J.-K. J. Chem. Thermodynamics 1993, 25, 711]717. 8. Wang, Z.-C.; Tian, Y.-W.; Yu, H.-L.; Zhang, X.-H.; Zhou, J.-K. Metall. Mater. Trans. B 1994, 25B, 103]109. 9. Wang, Z.-C.; Yu, H.-L.; Hu, Y.-F. J. Chem. Thermodynamics 1994, 26, 171]176. 10. Hu, Y.-F.; Wang, Z.-C. J. Chem. Thermodynamics 1994, 26, 429]433. 11. Hu, Y.-F.; Wang, Z.-C. J. Chem. Thermodynamics 1997, 29 879]884. 12. Wang, Z.-C. Acta Metall. Sinica 1980, 16, 195]206. 13. Wang, Z.-C. Acta Metall. Sinica 1981, 17, 168]176. 14. Wang, Z.-C. First China-USA Bilateral Metallurgical Conference. Metall. Ind. Press, The Chinese Society of Metals: Beijing. 1981, pp. 121]136. 15. Wang, Z.-C. Acta Metall. Sinica 1982, 18, 141]152. 16. Wang, Z.-C.; Luck, ¨ R.; Predel, B. J. Chem. Soc. Faraday Trans. 1990, 86, 3641]3646.
(Recei¨ ed 16 September 1997; in final form 9 December 1997)
O-701