- Email: [email protected]
Excess molar volumes and excess partial molar volumes of {xC6H5CH3+ (1−x)H(CH2)v(OCH2CH2)3OH} (v= 1,2, and 4) at the temperature 298.15 K
J. Chem. Thermodynamics 1996, 28, 717–722
Excess molar volumes and excess partial molar volumes of {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} (n=1, 2, and 4) at the temperature 298.15 K A. Pal a and W. Singh Department of Chemistry, Kurukshetra University, Kurukshetra-132 119 , India The excess molar volumes VmE for binary liquid mixtures of {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} for n = 1, 2, and 4 have been measured using a continuous-dilution dilatometer over the entire mole fraction x range at T = 298.15 K. The excess volume curves for these three mixtures are sigmoid shaped with a maximum in the toluene-rich region. The measured excess molar volume decreases as the alkyl chain length of the alkoxyethanol increases. The results have been used to estimate the excess partial molar volumes of the components. 7 1996 Academic Press Limited
1. Introduction In recent years, much effort has been made with the measurement, analysis, and interpretation of the excess thermodynamic functions of some mixtures of an alkoxyethanol with an organic solvent.(1–3) In a continuation of these investigations,(4–6) we report here the excess molar volumes VmE for binary mixtures of {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} for n = 1, 2, and 4 at T = 298.15 K. As far as we know, the only previous VmE measurements related to our work are those of Casanova et al.(7) on {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )2OH} for n=1, 2, and 4 at T=298.15 K. Therefore, we thought it worthwhile to undertake the present study in order to determine the effect of the enlargement of the polar head group by the addition of an –O(CH2CH2 )– unit, with a common alkyl chain; and the variation of the alkyl chain length with a common polar head group for the two homologous series.
2. Experimental Toluene (S.D. Fine Chemicals, HPLC grade, mole fraction: q0.997) was purified as described by Rastogi et al.(8) The purity of the final sample was checked by measuring the density with a bicapillary pycnometer(9) at T = 298.15 K; density was reproducible to within 23·10−4 g·cm−3. The density of the purified sample of toluene at T = 298.15 K was 0.8624 g·cm−3, in good agreement with literature values.(10–12) The compounds: 2-[2-(2-Methoxyethoxy)ethoxy]ethanol, a
To whom correspondence should be addressed.
0021–9614/96/070717+06 $18.00/0
7 1996 Academic Press Limited
718 TABLE
x
A. Pal and W. Singh
1. Excess molar volumes VmE and partial molar volumes Vm,1 and Vm,2 {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} for n=1, 2, and 4 at T=298.15 K VmE cm3·mol−1
0.0368 0.1027 0.1584 0.2111 0.2751 0.3173
−0.020 −0.050 −0.072 −0.090 −0.111 −0.120
0.5933 0.6403 0.6702 0.7090 0.7404 0.7711 0.8032
−0.088 −0.067 −0.055 −0.037 −0.021 −0.005 0.014
Vm,1 cm3·mol−1
Vm,2 cm3·mol−1
x
VmE cm3·mol−1
Vm,1 cm3·mol−1
Vm,2 cm3·mol−1
106.726 106.795 106.851 106.900 106.916
157.116 157.153 157.200 157.276 157.317
106.961 106.946 106.929 106.908 106.895 106.868 106.849
157.710 157.861 158.009 158.194 158.323 158.632 158.950
−0.148 −0.149 −0.146 −0.140 −0.129 −0.104
106.665 106.726 106.767 106.796 106.821 106.864
175.182 175.191 175.199 175.208 175.219 175.239
0.015 0.022 0.030 0.033 0.027 0.016
106.903 106.892 106.877 106.867 106.854 106.844
175.642 175.746 175.889 176.019 176.194 176.429
{xC6 H5CH3+(1−x)CH3 (OCH2CH2 )3OH} Run I 106.340 156.908 0.4066 −0.130 106.468 156.647 0.4551 −0.128 106.459 156.723 0.5065 −0.118 106.460 156.850 0.5771 −0.098 106.514 156.980 0.6133 −0.080 106.576 157.038 Run II 106.907 157.294 0.8381 0.031 106.927 157.348 0.8700 0.047 106.937 157.382 0.8932 0.056 106.950 157.429 0.9161 0.061 106.959 157.471 0.9296 0.062 106.966 157.523 0.9562 0.056 106.967 157.596 0.9786 0.029 {xC6 H5CH3+(1−x)H(CH2 )2 (OCH2CH2 )3OH} Run I
0.0467 0.0920 0.1342 0.2308 0.2802 0.3750
−0.026 −0.048 −0.066 −0.106 −0.123 −0.144
106.348 106.413 106.418 106.436 106.481 106.610
0.6610 0.7130 0.7524 0.7965 0.8255 0.8513 0.8788
−0.106 −0.082 −0.065 −0.038 −0.023 −0.009 0.008
106.861 106.889 106.907 106.922 106.926 106.924 106.915
174.923 174.780 174.828 175.029 175.096 175.172
0.4150 0.4667 0.5110 0.5485 0.5893 0.6656 Run II 175.237 0.9007 175.252 0.9174 175.271 0.9363 175.313 0.9510 175.363 0.9680 175.430 0.9873 175.532
{xC6 H5CH3+(1−x)H(CH2 )4 (OCH2CH2 )3OH} Run I 0.0270 0.1000 0.1628 0.2133 0.2683 0.3208 0.3836
−0.019 −0.064 −0.096 −0.120 −0.147 −0.159 −0.180
106.129 106.325 106.339 106.349 106.387 106.443 106.517
208.729 208.556 208.717 208.860 208.960 208.992 208.971
0.6733 0.7318 0.7554 0.8029 0.8376 0.8754
−0.180 −0.160 −0.149 −0.119 −0.097 −0.062
106.746 106.800 106.823 106.863 106.883 106.892
208.677 208.608 208.584 208.555 208.566 208.628
for
0.4304 0.4767 0.5288 0.5794 0.6491 0.6933
−0.194 −0.197 −0.202 −0.196 −0.186 −0.175
106.568 106.608 106.645 106.677 106.726 106.764
208.932 208.886 208.833 208.781 208.705 208.653
Run II 0.9035 0.9289 0.9493 0.9667 0.9791 0.9984
−0.036 −0.016 −0.003 0.004 0.008 0.003
106.887 106.876 106.864 106.854 106.847 106.842
208.723 208.856 209.001 209.155 209.287 209.543
VmE of {xC6 H5 CH3+(1−x)H(CH2 )n (OCH2 CH2 )3 OH}
719
FIGURE 1. Excess molar volume VmE for {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} at T=298.15 K: w, n=1; r, n=2; q, n=4.
CH3(OCH2CH2)3OH, 2-[2-(2-ethoxyethoxy)ethoxy]ethanol, H(CH2)2(OCH2CH2)3OH, and 2-[2-(2-butoxyethoxy)ethoxy]ethanol, H(CH2 )4 (OCH2CH2 )3OH, were the same as those used in the work.(13) Densities of the three alkoxyethanols were taken from our previous paper.(13) Prior to the measurements, all liquids were kept on 0.4 nm molecular sieves to reduce water content, and were partially degassed under vacuum. The measurements of VmE were carried out in a continuous-dilution dilatometer similar to that described by Dickinson et al.(14) Calibration and operational procedures have been described elsewhere.(9,15) The measured VmE s were accurate to 20.003 cm3·mol−1. All the measurements were made in a thermostatically controlled, well stirred water bath, whose temperature was controlled to 20.01 K. The composition of each mixture was obtained from the measured apparent masses of the components with an accuracy of 10−4·x. All masses were calculated from apparent masses. Each run covered just over half of the range of x so as to give an overlap between two runs.
3. Results and discussion The experimental results of VmE {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} for n=1, 2, and 4 at T=298.15 K are reported in table 1 and plotted as a function
720
A. Pal and W. Singh
TABLE 2. Parameters Ai and standard deviations s for least-squares representations by equation (1) of VmE for studied mixtures at T=298.15 K xC6 H5CH3+
A0
(1−x)CH3 (OCH2CH2 )3OH (1−x)H(CH2 )2 (OCH2CH2 )3OH (1−x)H(CH2 )4 (OCH2CH2 )3OH
A1
A2
A3
A4
A5
s
−0.4719 0.4824 0.4734 −0.3713 0.5489 1.2186 0.0022 −0.5837 0.2469 0.2983 −0.2492 0.5181 0.9689 0.0023 −0.7908 −0.0746 −0.0797 −0.3267 0.6598 1.1139 0.0026
of x in figure 1. For each mixture, the excess quantities were fitted with an empirical equation of the form: n
VmE /(cm3·mol−1 )=x(1−x) s Ai (2x−1)i.
(1)
i=0
The values of the coefficients Ai of equation (1), obtained by the method of least squares with all points weighted equally, are given in table 2 along with standard deviations s. E We have also calculated excess partial molar volumes Vm,1 =(Vm,1−V* m,1 ) and E E Vm,2 =(Vm,2−V* ) from V where V* and V* represent the molar volumes m,2 m,1 m,2 m of the pure components. The partial molar volumes Vm,1 and Vm,2 are given in E E table 1, while figure 3 shows the excess partial molar volumes Vm,1 and Vm,2 plotted against x.
FIGURE 2. Plot of VmE (x = 0.5) against n: i, {0.5C6 H5CH3+0.5H(CH2 )n (OCH2CH2 )2OH} from reference 7; W, {0.5C6 H5CH3+0.5H(CH2 )n (OCH2CH2 )3OH}.
VmE of {xC6 H5 CH3+(1−x)H(CH2 )n (OCH2 CH2 )3 OH}
E E FIGURE 3. Excess partial molar volumes Vm,1 and Vm,2 (1−x)H(CH2 )n (OCH2CH2 )3OH} at T=298.15 K: A, n=1; B, n=2; C, n=4.
721
for
{xC6 H5CH3 +
Excess volume against composition plots in figure 1 show that VmE changes sign for these three mixtures, being negative at lower values of x and positive for higher values of x. For the same value of x, the excess VmE decreases as the chain length of the alkoxyethanol increases. Alkoxyethanols self-associate, like alcohols. The presence of the etheric oxygen enhances the ability of the –OH group of the alkoxyethanols(16) to form hydrogen bonds with toluene and hence results in a contraction in volume. Again, due to the electron-donating inductive effect of the alkyl group, the strength of bonding in alkoxyethanols increases with an increase in chain length. The behaviour is similar to that with 2-(2-alkoxyethoxy)ethanols(7) and n-alkanols(17) which exhibit sigmoid and less unsymmetrical VmE s skewed towards high values of x. In figure 2 is plotted the equimolar excess molar volume, VmE (x=0.5) against n. This dependence is nearly linear with negative slope for the homologous series. Remarkably, the difference between the equimolar excess volumes of the mixtures formed with the members of each homologous series of the alkoxyethanol with the same aliphatic chain decreases due to each addition of a –OCH2CH2 – group.
722
A. Pal and W. Singh
E The composition dependence of Vm,i illustrated in figure 3 is typical of mixtures E of an organic solvent and an amphiphilic molecule. There is a sharp decrease in Vm,2 E (amphiphile) at higher x as compared with the behaviour of Vm,1 (toluene) at low x. This reflects the structural changes of toluene introduced by alkoxyethanol molecules. Such an explanation is consistent with that of the VmE in figure 1.
W. Singh is grateful to the Council of Scientific and Industrial Research, New Delhi for awarding a Senior Research Fellowship. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
Pal, A.; Singh, W. Indian J. Chem. 1995, 34A, 389–392. Pal, A.; Singh, W. J. Chem. Eng. Data 1995, 40, 1130–1133. Pal, A.; Sharma, H. K.; Singh, W. Indian J. Chem. 1995, 34A, 987–989. Pal, A.; Singh, W. J. Chem. Eng. Data 1996, 41, 181–184. Pal, A.; Singh, W. J. Chem. Thermodynamics 1996, 28, 143–151. Pal, A.; Singh, W. J. Chem. Thermodynamics 1996, 28, 337–341. Barbes, B.; Garcia, I.; Gonzalez, J. A.; Cobos, J. C.; Casanova, C. J. Chem. Thermodynamics 1994, 26, 791–795. Rastogi, R. P.; Nath, J.; Misra, R. R. J. Chem. Thermodynamics 1971, 3, 307–317. Pal, A.; Singh, Y. P. J. Chem. Thermodynamics 1994, 26, 1063–1070. Riddick, J. A., Bunger, W. B. Organic Solvents, Techniques of Organic Chemistry, Vol. II. Weissberger, A.: editor. Wiley-Interscience: New York. 1970. Nigam, R. K.; Singh, P. P. Trans. Faraday Soc. 1969, 65, 950–964. Aralaguppi, M. I.; Aminabhavi, T. M.; Balundgi, R. H. Fluid Phase Equilib. 1992, 71, 99–112. Pal, A.; Singh, Y. P. J. Chem. Thermodynamics 1995, 27, 1329–1336. Dickinson, E.; Hunt, D. C.; McLure, I. A. J. Chem. Thermodynamics 1975, 7, 731–740. Pal, A.; Singh, Y. P.; Singh, W. Indian J. Chem. 1994, 33A, 1083–1087. Buckley, P.; Brochu, M. Can. J. Chem. 1972, 50, 1149–1156. Raman, G. K.; Narayana Swamy, G.; Dharmaraju, G. Int. DATA Series, Ser. A., Selected Data on Mixtures 1988, 3, 152–159.
(Received 28 November 1995; in final form 8 February 1996)
O-614
Excess molar volumes and excess partial molar volumes of {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} (n=1, 2, and 4) at the temperature 298.15 K A. Pal a and W. Singh Department of Chemistry, Kurukshetra University, Kurukshetra-132 119 , India The excess molar volumes VmE for binary liquid mixtures of {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} for n = 1, 2, and 4 have been measured using a continuous-dilution dilatometer over the entire mole fraction x range at T = 298.15 K. The excess volume curves for these three mixtures are sigmoid shaped with a maximum in the toluene-rich region. The measured excess molar volume decreases as the alkyl chain length of the alkoxyethanol increases. The results have been used to estimate the excess partial molar volumes of the components. 7 1996 Academic Press Limited
1. Introduction In recent years, much effort has been made with the measurement, analysis, and interpretation of the excess thermodynamic functions of some mixtures of an alkoxyethanol with an organic solvent.(1–3) In a continuation of these investigations,(4–6) we report here the excess molar volumes VmE for binary mixtures of {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} for n = 1, 2, and 4 at T = 298.15 K. As far as we know, the only previous VmE measurements related to our work are those of Casanova et al.(7) on {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )2OH} for n=1, 2, and 4 at T=298.15 K. Therefore, we thought it worthwhile to undertake the present study in order to determine the effect of the enlargement of the polar head group by the addition of an –O(CH2CH2 )– unit, with a common alkyl chain; and the variation of the alkyl chain length with a common polar head group for the two homologous series.
2. Experimental Toluene (S.D. Fine Chemicals, HPLC grade, mole fraction: q0.997) was purified as described by Rastogi et al.(8) The purity of the final sample was checked by measuring the density with a bicapillary pycnometer(9) at T = 298.15 K; density was reproducible to within 23·10−4 g·cm−3. The density of the purified sample of toluene at T = 298.15 K was 0.8624 g·cm−3, in good agreement with literature values.(10–12) The compounds: 2-[2-(2-Methoxyethoxy)ethoxy]ethanol, a
To whom correspondence should be addressed.
0021–9614/96/070717+06 $18.00/0
7 1996 Academic Press Limited
718 TABLE
x
A. Pal and W. Singh
1. Excess molar volumes VmE and partial molar volumes Vm,1 and Vm,2 {xC6 H5CH3+(1−x)H(CH2 )n (OCH2CH2 )3OH} for n=1, 2, and 4 at T=298.15 K VmE cm3·mol−1
0.0368 0.1027 0.1584 0.2111 0.2751 0.3173
−0.020 −0.050 −0.072 −0.090 −0.111 −0.120
0.5933 0.6403 0.6702 0.7090 0.7404 0.7711 0.8032
−0.088 −0.067 −0.055 −0.037 −0.021 −0.005 0.014
Vm,1 cm3·mol−1
Vm,2 cm3·mol−1
x
VmE cm3·mol−1
Vm,1 cm3·mol−1
Vm,2 cm3·mol−1
106.726 106.795 106.851 106.900 106.916
157.116 157.153 157.200 157.276 157.317
106.961 106.946 106.929 106.908 106.895 106.868 106.849
157.710 157.861 158.009 158.194 158.323 158.632 158.950
−0.148 −0.149 −0.146 −0.140 −0.129 −0.104
106.665 106.726 106.767 106.796 106.821 106.864
175.182 175.191 175.199 175.208 175.219 175.239
0.015 0.022 0.030 0.033 0.027 0.016
106.903 106.892 106.877 106.867 106.854 106.844
175.642 175.746 175.889 176.019 176.194 176.429
{xC6 H5CH3+(1−x)CH3 (OCH2CH2 )3OH} Run I 106.340 156.908 0.4066 −0.130 106.468 156.647 0.4551 −0.128 106.459 156.723 0.5065 −0.118 106.460 156.850 0.5771 −0.098 106.514 156.980 0.6133 −0.080 106.576 157.038 Run II 106.907 157.294 0.8381 0.031 106.927 157.348 0.8700 0.047 106.937 157.382 0.8932 0.056 106.950 157.429 0.9161 0.061 106.959 157.471 0.9296 0.062 106.966 157.523 0.9562 0.056 106.967 157.596 0.9786 0.029 {xC6 H5CH3+(1−x)H(CH2 )2 (OCH2CH2 )3OH} Run I
0.0467 0.0920 0.1342 0.2308 0.2802 0.3750
−0.026 −0.048 −0.066 −0.106 −0.123 −0.144
106.348 106.413 106.418 106.436 106.481 106.610
0.6610 0.7130 0.7524 0.7965 0.8255 0.8513 0.8788
−0.106 −0.082 −0.065 −0.038 −0.023 −0.009 0.008
106.861 106.889 106.907 106.922 106.926 106.924 106.915
174.923 174.780 174.828 175.029 175.096 175.172
0.4150 0.4667 0.5110 0.5485 0.5893 0.6656 Run II 175.237 0.9007 175.252 0.9174 175.271 0.9363 175.313 0.9510 175.363 0.9680 175.430 0.9873 175.532
{xC6 H5CH3+(1−x)H(CH2 )4 (OCH2CH2 )3OH} Run I 0.0270 0.1000 0.1628 0.2133 0.2683 0.3208 0.3836
−0.019 −0.064 −0.096 −0.120 −0.147 −0.159 −0.180
106.129 106.325 106.339 106.349 106.387 106.443 106.517
208.729 208.556 208.717 208.860 208.960 208.992 208.971
0.6733 0.7318 0.7554 0.8029 0.8376 0.8754
−0.180 −0.160 −0.149 −0.119 −0.097 −0.062
106.746 106.800 106.823 106.863 106.883 106.892
208.677 208.608 208.584 208.555 208.566 208.628
for
0.4304 0.4767 0.5288 0.5794 0.6491 0.6933
−0.194 −0.197 −0.202 −0.196 −0.186 −0.175
106.568 106.608 106.645 106.677 106.726 106.764
208.932 208.886 208.833 208.781 208.705 208.653
Run II 0.9035 0.9289 0.9493 0.9667 0.9791 0.9984
−0.036 −0.016 −0.003 0.004 0.008 0.003
106.887 106.876 106.864 106.854 106.847 106.842
208.723 208.856 209.001 209.155 209.287 209.543
VmE of {xC6 H5 CH3+(1−x)H(CH2 )n (OCH2 CH2 )3 OH}
719
FIGURE 1. Excess molar volume VmE for {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} at T=298.15 K: w, n=1; r, n=2; q, n=4.
CH3(OCH2CH2)3OH, 2-[2-(2-ethoxyethoxy)ethoxy]ethanol, H(CH2)2(OCH2CH2)3OH, and 2-[2-(2-butoxyethoxy)ethoxy]ethanol, H(CH2 )4 (OCH2CH2 )3OH, were the same as those used in the work.(13) Densities of the three alkoxyethanols were taken from our previous paper.(13) Prior to the measurements, all liquids were kept on 0.4 nm molecular sieves to reduce water content, and were partially degassed under vacuum. The measurements of VmE were carried out in a continuous-dilution dilatometer similar to that described by Dickinson et al.(14) Calibration and operational procedures have been described elsewhere.(9,15) The measured VmE s were accurate to 20.003 cm3·mol−1. All the measurements were made in a thermostatically controlled, well stirred water bath, whose temperature was controlled to 20.01 K. The composition of each mixture was obtained from the measured apparent masses of the components with an accuracy of 10−4·x. All masses were calculated from apparent masses. Each run covered just over half of the range of x so as to give an overlap between two runs.
3. Results and discussion The experimental results of VmE {xC6 H5CH3 + (1−x)H(CH2 )n (OCH2CH2 )3OH} for n=1, 2, and 4 at T=298.15 K are reported in table 1 and plotted as a function
720
A. Pal and W. Singh
TABLE 2. Parameters Ai and standard deviations s for least-squares representations by equation (1) of VmE for studied mixtures at T=298.15 K xC6 H5CH3+
A0
(1−x)CH3 (OCH2CH2 )3OH (1−x)H(CH2 )2 (OCH2CH2 )3OH (1−x)H(CH2 )4 (OCH2CH2 )3OH
A1
A2
A3
A4
A5
s
−0.4719 0.4824 0.4734 −0.3713 0.5489 1.2186 0.0022 −0.5837 0.2469 0.2983 −0.2492 0.5181 0.9689 0.0023 −0.7908 −0.0746 −0.0797 −0.3267 0.6598 1.1139 0.0026
of x in figure 1. For each mixture, the excess quantities were fitted with an empirical equation of the form: n
VmE /(cm3·mol−1 )=x(1−x) s Ai (2x−1)i.
(1)
i=0
The values of the coefficients Ai of equation (1), obtained by the method of least squares with all points weighted equally, are given in table 2 along with standard deviations s. E We have also calculated excess partial molar volumes Vm,1 =(Vm,1−V* m,1 ) and E E Vm,2 =(Vm,2−V* ) from V where V* and V* represent the molar volumes m,2 m,1 m,2 m of the pure components. The partial molar volumes Vm,1 and Vm,2 are given in E E table 1, while figure 3 shows the excess partial molar volumes Vm,1 and Vm,2 plotted against x.
FIGURE 2. Plot of VmE (x = 0.5) against n: i, {0.5C6 H5CH3+0.5H(CH2 )n (OCH2CH2 )2OH} from reference 7; W, {0.5C6 H5CH3+0.5H(CH2 )n (OCH2CH2 )3OH}.
VmE of {xC6 H5 CH3+(1−x)H(CH2 )n (OCH2 CH2 )3 OH}
E E FIGURE 3. Excess partial molar volumes Vm,1 and Vm,2 (1−x)H(CH2 )n (OCH2CH2 )3OH} at T=298.15 K: A, n=1; B, n=2; C, n=4.
721
for
{xC6 H5CH3 +
Excess volume against composition plots in figure 1 show that VmE changes sign for these three mixtures, being negative at lower values of x and positive for higher values of x. For the same value of x, the excess VmE decreases as the chain length of the alkoxyethanol increases. Alkoxyethanols self-associate, like alcohols. The presence of the etheric oxygen enhances the ability of the –OH group of the alkoxyethanols(16) to form hydrogen bonds with toluene and hence results in a contraction in volume. Again, due to the electron-donating inductive effect of the alkyl group, the strength of bonding in alkoxyethanols increases with an increase in chain length. The behaviour is similar to that with 2-(2-alkoxyethoxy)ethanols(7) and n-alkanols(17) which exhibit sigmoid and less unsymmetrical VmE s skewed towards high values of x. In figure 2 is plotted the equimolar excess molar volume, VmE (x=0.5) against n. This dependence is nearly linear with negative slope for the homologous series. Remarkably, the difference between the equimolar excess volumes of the mixtures formed with the members of each homologous series of the alkoxyethanol with the same aliphatic chain decreases due to each addition of a –OCH2CH2 – group.
722
A. Pal and W. Singh
E The composition dependence of Vm,i illustrated in figure 3 is typical of mixtures E of an organic solvent and an amphiphilic molecule. There is a sharp decrease in Vm,2 E (amphiphile) at higher x as compared with the behaviour of Vm,1 (toluene) at low x. This reflects the structural changes of toluene introduced by alkoxyethanol molecules. Such an explanation is consistent with that of the VmE in figure 1.
W. Singh is grateful to the Council of Scientific and Industrial Research, New Delhi for awarding a Senior Research Fellowship. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
Pal, A.; Singh, W. Indian J. Chem. 1995, 34A, 389–392. Pal, A.; Singh, W. J. Chem. Eng. Data 1995, 40, 1130–1133. Pal, A.; Sharma, H. K.; Singh, W. Indian J. Chem. 1995, 34A, 987–989. Pal, A.; Singh, W. J. Chem. Eng. Data 1996, 41, 181–184. Pal, A.; Singh, W. J. Chem. Thermodynamics 1996, 28, 143–151. Pal, A.; Singh, W. J. Chem. Thermodynamics 1996, 28, 337–341. Barbes, B.; Garcia, I.; Gonzalez, J. A.; Cobos, J. C.; Casanova, C. J. Chem. Thermodynamics 1994, 26, 791–795. Rastogi, R. P.; Nath, J.; Misra, R. R. J. Chem. Thermodynamics 1971, 3, 307–317. Pal, A.; Singh, Y. P. J. Chem. Thermodynamics 1994, 26, 1063–1070. Riddick, J. A., Bunger, W. B. Organic Solvents, Techniques of Organic Chemistry, Vol. II. Weissberger, A.: editor. Wiley-Interscience: New York. 1970. Nigam, R. K.; Singh, P. P. Trans. Faraday Soc. 1969, 65, 950–964. Aralaguppi, M. I.; Aminabhavi, T. M.; Balundgi, R. H. Fluid Phase Equilib. 1992, 71, 99–112. Pal, A.; Singh, Y. P. J. Chem. Thermodynamics 1995, 27, 1329–1336. Dickinson, E.; Hunt, D. C.; McLure, I. A. J. Chem. Thermodynamics 1975, 7, 731–740. Pal, A.; Singh, Y. P.; Singh, W. Indian J. Chem. 1994, 33A, 1083–1087. Buckley, P.; Brochu, M. Can. J. Chem. 1972, 50, 1149–1156. Raman, G. K.; Narayana Swamy, G.; Dharmaraju, G. Int. DATA Series, Ser. A., Selected Data on Mixtures 1988, 3, 152–159.
(Received 28 November 1995; in final form 8 February 1996)
O-614