Indian Journal of Chemistry Vol 39A, August 2000, pp.809 - 818

Excess volumes, viscosities and compressibilities of binary mixtures consisting of alcohols with l,4-dioxane at different temperatures

T S Banipal' & Arnrit Pal Toort

Department of PharmaceuticaJ Sciences, Guru Nanak Dev University, Amritsar 143 005, India

and

V K Rattan

Department of Chemical Engineering and Technology, Panjab University, Chandigarh 160014, India

Received 15 February 1999; revised 17 December 1999

The densities , viscosities and ultrasonic velocities of binary mixtures of methanol (MeOH), butanol (BuOH) and isobutanol (iso-BuOH) with 1,4-dioxane (D) have been determined at 298.15, 303.15, 308.15 and 313.15K over the whole composition range using vibrating-tube densitymeter, Ubbelohde viscometer and ultrasonic interferometer respectively. TIlese data have been utilized to estimate the excess volume (V E), excess viscosity (TI E), excess cOrllpressibi lity (K,E), excess Gibbs free energy of activation of flow (G E) and Grunberg and Nissan parameter (d). Enthalpy (Ml*), entropy (~*) and free energy (t..G*) of activation of viscous flow have also been estimated usi ng Eyring' s equation from viscosity and density data. V E values for MeOH-D system are negative at 298.15K over the entire composition range and at higher temperature, V E plots become S shaped with VE vaJues positive at lower mole fraction of alcohol. V E values are positive for BuOH-D and iso-BuOH-D systems over the entire cOf'lposition range and for all the systems they increase with 0 increase in temperature. TI E values are negative for all the systems and magnitude of TIE decreases with increase in temperature in aJl the cases. KSE values are negative for all the systems (except for BuOH-D system at 298.15K only) over the whole composi tion range. Analysis of these results suggests the absence of any strong specific interactions.

Excess thermodynamic functions of mixtures of cyclic ethers in polar and non-polar solvents have gained considerable interest because these compounds are good solvents I - I I. From the study of excess functions for the solutions of I ,4-dioxane with various solvents it has been established l

-3,6.8 that there

exists specific interactions in 1,4-dioxane + aromatic hydrocarbon and + haloalkane mixtures. Recently Letcher et ai.8ol1 have studied excess molar enthalpies of the mixtures consisting of an alkanol + a branched chain ether and suggested a relatively strong association between alkanol and ether. Similarly they have interpreted the positive excess enthalpies for alkanol + cyclic ether in terms of strong self­association exhibited by the alkanols and the cross­association of the O---HO specific interaction. However, to the best of our knowledge data on excess viscosities, compressibi lities and volumes of such systems are not available. Therefore, we planned to study these excess functions for mixtures consisting

t present add ress: Department of Chemi cal Engineeri ng, Thapar Institute of Engineering & Technology, Pat iaJ a.

of 1,4-dioxane + alkanols which may further throw

light on the nature of heteromolecular interactions occurring in these systems. The present paper reports the densities, viSCOSIties, ultrasonic velocities, compressibilities, and excess volumes, viscosities and compressibilites of binaries of l,4-dioxane (D) with methanol (MeOH), butanol (BuOH) and isobutanol (iso-BuOH) at 298.15, 303.15, 308 .15 and 3 13.15K.

Materials and Methods Methanol (LR), 1,4-dioxane (LR) (both from

Merck) and butanol (LR) and iso-butanol (LR) (both from BDH) were purified using fractionating column 12. 13 and middle fraction s were collected and stored over molecular sieves . The purity of the samples was checked by density and viscosity measurements I3

,14.

Densities were measured using vibrating-tube digital densi ty meter (DMA 48, Anton Paar, Austria). The details of its principle and working have been described elsewhere l5

. The vibrating-tube containing sample was kept at constant temperature by in-built solid state thermostat within ± 0.01 K. Densi tymeter

810 INDIAN J CHEM, SEC. A, AUGUST 2000

has an accuracy of I x I 0-4 g em -3 for a measurement

range of 0.5 to 1.5 g cm-3. Viscosity was detennin~d

using Ubbelohde viscometer l6-18 which was

calibrated with benzene and doubly distilled water at

all four temperatures. The values are accurate to ± 0.001 cPo Velocities were determined using ultrasonic interferometer (Model M-82, Mittal Enterprises, India) working at 3 MHz. The principle used in measurement of ultrasonic velocity through medium is based on the accurate determination of wavelength of ultrasonic waves of known frequency produced by quartz crystal in measuring cell l9

. The ultrasonic interferometer has an accuracy of ± 0.5 m S- I. The temperature of the solution was controlled by circulating water through the jacket of double walled cell. Measurements were made using constant temperature bath within ± 0.0 I K. All solvents were degassed before use and mixtures were prepared on mass basis.

Results The experimental data on densities (p), viscosities

(11) and sound velocities (u) for binary mixtures of MeOH, BuOH and iso-BuOH with D at 298. I 5, 303.15,308. 15 and 313. 15K were detennined. From the measured values of density, molar volume (V rrJ was calculated using the relat ion:

... (I)

where X" X2 and M" M2 are the mole fractions and molecular weights of the components 1 and 2 respectively. The excess volumes (V E) for these binary mixtures were obtained using the relation:

... (2)

where PI and P2 are the densities of pure components 1 and 2 respectively . From densities and efflux times (t), the viscosities (11) were obtained using the relation :

11 = P (At-BIt) .. . (3)

where A and Bare viscometric constants. Excess viscosities (l1 E) were obtained as follows :

... (4)

where 111 and 112 are the viscosities of pure

components I and 2 respectively and 11 IS the viscosity of the mixture.

The parameter d, regarded as a measure of the strength of interaction between components of the binary mixtures, has been estimated using relationship proposed by Grunberg and Nissan20 as follows:

... (5)

The excess Gibbs free energy of acti vation of flow (CE) was obtained

where VI and V2 are the molar volumes of the pure components I and 2 respectively. The values of

densities (p) and ultrasonic velocities (u) were used to calculate compressibi lities (Ks) by using the relation:

... (7)

Excess compressibil ities (Ks E) were obtained using the relation:

... (8)

where Ks is the compressibi lity of the mixture and K~I and KS2 are the compressibilit ies of pure components) and 2 respectively.

The values of V E,l1E, Ks E, C E and d as a function of mole fraction are given in Tables 1-3 . Plots of V E, 11 , llE and Ks E are shown in Figs 1-4. All the excess properties were fitted by the method of least squares to Redlich-Kister type equation:

... (9)

where A E is the excess property, Aj is a polynomial coefficient and n is the polynomial degree. The values of coefficients of Eq. 9 for V E, ll E, KsE and C E along

with the values of standard deviat ion (a) are presented in Tables 4-6.

The enthalpy (fl.H* ) and entropy (M*) of activation of viscous flow of liquid mixtures are related to the corresponding viscosity by the Eyring's

. 21 equatIon :

In (v M) = [In hN - M*IR] + fl.H*IRT ... (10)

.r

)

BANIPAL et al. ; EXCESS FUNCTIONS OF BINARY MIXTURES OF ALCOHOLS & 1,4-DIOXANE 811

Table I-Excess volumes (V E), excess viscosities (r{), excess compressibilities (I(. E) and excess Gibbs free energy for activation of flow (CE) for (x) methanol + (I-x) I, 4-dioxane system at different temperatures

x VE TJE KsE 'C E d cm3 mol-I cp 10-12m2N-1 cal mol-I

298.15 K

0.1044 -<l.0796 -<l.0369 -30.335 6.55 -<l.10 0.2240 -<l.1707 -<l.0744 -74.907 7.45 -<l.15 0.3192 -<l.2264 -<l.0939 -93.886 7.16 -<l.18 0.3990 -<l.2904 -<l.0928 -114.017 13.61 -<l. 15 0.5185 -<l.3195 -<l.0887 -135.298 18.38 -<l.13 0.6073 -<l.3081 -<l.0816 -142.698 19.15 -<l.13 0.7097 -<l.3016 -<l.0669 -136.293 18.60 -<l.12 0.8002 -<l.2645 -<l.0489 -118.770 16.58 -<l.11 0.8935 -<l.1941 -<l.0313 -92.276 7.05 ' -<l.17

303.15 K

0.1044 0.0993 -<l.0399 -36.026 2.86 -<l.19 0.2240 -<l.0778 -<l.0685 -75.957 5.45 -<l.18 0.3192 -<l.1551 -<l.0832 -105.689 6.56 -<l.19 0.3990 -<l.2182 -<l.0826 -125 .024 12.53 -<l.16 0.5185 -<l.255 I -<l.0778 -141.489 18.17 -<l.13 0.6073 -<l.2890 -<l.0727 -150.156 17.53 -<l.14 0.7097 -<l.2792 -<l.0590 -143.090 17.89 -<l. 13 0.8002 -<l.2387 -<l.0470 -127.215 12.11 -<l.16 0.8935 -<l.1466 -<l.0283 -91.805 6.57 -<l.19

308.15K 0.1044 0.1361 -<l.0467 -42.074 -6.05 -<l.35 0.2240 0.0076 -<l.0649 -84.704 0.55 -<l.24 0.3192 -<l.0696 -<l.0755 -117.775 2.94 -<l.22 0.3990 -<l.1324 -<l.074 I -135.040 9.43 -<l. 19 0.5185 -<l.20 15 -<l.0713 -152.785 13.16 -<l.18 0.6073 -<l.2334 -<l.0647 -162.470 14.79 -<l.17 0.7097 -<l.2435 -<l.0540 -158.018 13 .78 -<l.17 0.8002 -<l.21 45 -<l.0445 -134.393 7.04 -<l.22 0.8935 -<l. 1260 -<l.0250 -96.214 5.82 -<l.21

313.15K

0.1044 0.2468 -<l.0419 -46.189 -7.00 -<l.38 0.2240 0.0847 -{).0629 -93 .214 -6.03 -<l.30 0.3192 0.0160 -<l.0698 -124.296 -2.13 -<l.27 0.3990 -<l.0789 -<l.0704 -140.150 1.89 -<l.24 0.51 85 -<l.1587 -<l.0676 - 159.985 5.46 -<l.23 0.6073 -<l.1827 -<l.0632 -173.249 5.48 -<l.24 0.7097 -<l.1952 -<l.0518 -163.192 6.74 -<l.23 0.8002 -<l.1737 -<l.0420 - 141.086 2.36 -<l.27 0.8935 - 0.1171 -<l.0240 -97.232 2.30 -<l.27

where M = X tMt + X2M2, h is Planck's constant, N is intercept of linear plot of In (vM) vs liT according to AvogadiO's number -and v is kinematic viscosity. above equation. Then free energy of activation of Within the temperature range of this study MI* and viscous flow (~G*) has been estimated using the Eq. M* are assumed to be constant and thus the values of (11) at different temperatures:

Ml* and M * can be determined from the slope and ~G* = MI* - T M* ... (11)

812 INDIAN J CHEM, SEC. A, AUGUST 2000

Table 2 - Excess volumes CV E), excess viscosities CO E), excess compressibilities (K,E) and excess Gibbs free energy for activation of flow (CE

) for (x) butanol + (I-x) I, 4-dioxane system at different temperatures

x V E T\E K,E C E d

0.0943 0. 1987 0.3037 0.4038 0.5944 0.6942 0.8085 0.9153

0.0943

0.1987 0.3037 0.4038 0.4911 0.5944 0.6942 0.8085 0.9153

0.0943 0.1987 0.3037 0.4098 0.4911 0.5944 0.6942 0.8085 0.9153

0.0943 0. 1987 0.3037 0.4038 0.4911 0.5944 0.6942 0.8085 0.9153

cm3mol- 1 cp 1O- 12m2N-1 cal mol- I

0.0881 0.1499 0.2019 0.2242 0.2252 0.1746 0.1217 0.0609

0.0967 0.1684 0.2159 0.2392 0.2567 0.2403 0.2192 0.1439 0.0701

0.1179 0.1 844 0.2224 0.2487 0.2633 0.2709 0.2385 0.1716 0.0965

0.1230 0.2043 0.2404 0.2747 0.2839 0.2885 0.2617 0.1 820 0.1033

298.15 K -0.1978 -0.3679 -0.4803 -0.5624 -0.6307 -0.6098 -0.5327 -0.3074

303.15 K -0.1280 -0.2488 -0.3522 -0.4253 -0.4819 -0.5107 -0.4858 -0.4644 -0.2885

308.15K -0.1180 -0.2383 -0.3157 -0.3784 -0.4197 -0.4442 -0.4316 -0.3879 -0.2553

313.15 K

2.163 4.769 7.499 9.648 7.152 4.615

-0.218 0.201

1.050 0.457

-1.311 -3 .143 -3.370 -3.099 -2.823 -2.243 -1.427

-5.961 -11.167 -12.100 - 13.724 -13.176 -11.531 -9.297 -7.743 -5.256

-0.1032 -10.590 -0.1953 -18.202

-0.2660 -19.587 -0.3335 -19.133 -0.3638 -18.559 -0.3823 -16.635 -0.3656 -13.039 -0.3459 - 10.829 -0.2125 -6.935

-73.63 -130.88 -158.22 -173.07 -169.26 -151.92 -122.83 -63.47

-50.39 -94.77

-129.51 -149.34 -163.85 -164.05 -144.71 -132.98 -75.22

-57.34 -115.12 -144.47 -165.76 -176.73 -177.05 -161.27 -135.92 -82.54

-62.48 -116.05 -153.70 -189.62 -199.22 -199.20 -178.52 -160.60 -89.23

- 1.47 -1.40 - 1.28 - 1.23 - 1.20 - 1.22 - 1.35 -1.39

- 1.00 - 1.01 - 1.03 - 1.05 - 1. 10 -1.15 - 1. 15 - 1.44 -1.62

-1.12 -1 .20 -1.13 -1.14 -1.17 -1.22 -1.26 -1.45 -1.75

-1.20 -1.19 -1.18 -1.28 -1.30 -1.34 -1.37 -1.68 -1.87

The values of I:l.G* (at 29!U5 K only), Ml* and !::.S* for various systems are given in the Table 7.

. MeOH. However, at higher temperatures i.e. at 303.15K and above the plot of V E becomes S shaped. In the lower mole fraction range (upto z 0.2) V E

values become positive having small magnitude (zO.1 cm) mol- J at 303.15K) and at higher mole fraction V E

values are still negative. With further rise in temperature magnitude of positive V E in the lower

Excess volumes (0) V E values for MeOH-D system (Fig 1) are negative

at 298.l 5K over the entire composition range and the minimum lies between 0.5 and 0.6 mole fraction of

)

BANIPAL et af.: EXCESS FUNCTIONS OF BINARY MIXTURES OF ALCOHOLS & 1,4-DIOXANE 813

Table 3-Excess volumes (V E), excess viscosities (TIE), excess compressibilites (K. E) and excess Gibbs free energy for activation of flow (G E) for (x) isobutanol + (I-x) I, 4-dioxane system at different temperatures.

x VE TIE KsE G E d

0.0643 0.1276 0.3027 0.3993 0.4932 0.5986 0.6991 0.8020 0.8980

0.0643 0.1276 0.3027 0.3993 0.4932 0.5986 0.6991 0.8020 0.8980

0.0643 0.1276 0.3027 0.3993 0.4932 0.5986 0.699 1 0.8020 0.8980

0.0643 0.1276 0.3027 0.3993 0.4932 0.5986 0.6991 0.8020 0.8980

cm3 mol-I cp 1O-12m2N- 1 cal mol-I

0.0319 0.0555 0.1400 0.1931 0.2256 0.2556 0.2191 0.1514 0.0941

0.0381 0.0657 0.1586 0.2096 0.2513 0.2707 0.2346 0.1679 0.0966

0.0394 0.0776 0.1669 0.2236 0.2624 0.2776 0.2586 0.1886 0.1071

0:0526 0.0998 0.2070 0.2504 0.2902 0.3165 0.2938 0.2180 0. 1279

298.15 K -0.1963 -1.489 -0.3779

-0.7785 -0.9471 -1.0333 -1.0261

-0.9989 -0.8873 -0.6867

-0.1834 -0.3565 -0.7258 -0.8265 -0.9139 -0.9149 -0.8832 -0.7506 -0.5076

-0.1626 -0.3184 -0.6188 -0.7185 -0.8003 -0.8195 -0.7580 -0.6386 -0.3988

-0.1439 -0.2853 -0.5330 -0.6168 -0.6499 -0.6762 -0.6265 -0.5258 -0.3344

-6.229 -12.915 -17.631 -19.204 -17.589 -14.897 -9.772 -4.058

303.15 K -3.260 -7.815

-16.251 -19.986 -19.957 -17.338 -14.574 -10.606 -4.764

308.15 K -5.432

-13.286 -21.216 -24.486 -23 .523 -22.406 -18.578 -12.958 -6.413

313 .15K -10.614 -15.876 -24.036 -27.037 -26.282 - 24.002 -20.390 - 15.837 -8.945

-56.10 -105.62 -191.96 -216.58 -211.81 -179.68 -158.66 -129.61 -96.19

-60.37 -115.95 -207.33 -205.66 -206.60 -178.20 -155.22 -118.20 -72.64

-61.44 -119.51 -195.73 -201.63 -205 .49 -185 .28 -149.13 -11 2.34 -61.29

- 67.34 -1 26.10 -193.56 -198.83 -1 82.38 -170.49 - 138.55 - 104.37 - 59.11

-1.58 -1.61 -1.55 -1.54 -1.44 -1 .28 -1 .29 -1 .39 -l.'79

-1.68 -1.74 -1.64 -1.44

-1.39 -1.25 -1.24 -1.25 -1.33

- 1.68 -1.76 -1.53 -1.39 -1.15 -1.28 -1.17 -1.17 -1.11

-1.81 -1.83 - 1.49 - 1.35 . -1. 19 -1.16 - 1.08 - 1.07 -1.05

mole fraction range increases and the magnitude of negative V E In the higher mole fraction range decreases with continaous shift of minimum towards higher mole fraction . For BuOH-D and iso-BuOH-D the V E values are posit ive over the entire composition range with the maxima slightly towards alcohol rich

region. The effect of temperature in these systems is almost same and V E values become more and more positive with the increase in temperature. However, it may be observed that the increase in V E with temperature is more in the case of MeOH-D system than in the case of BuOH and iso-BuOH systems.

~14 INDIAN J CHEM, SEC. A, AUGUST 2000

0.40..--- -----------------,- 0.4

0.35 _Scale ::':::.:::.-: - - Scale __

0.3

0.30 0.2

.; 0.25 0.1 '0 E ~

0.0 "E u

"" ~. 1 '>

"E 0.20 .~----'Ic u

~ 0.15

0.10 ~. 2

0.05 ~. 3

0.00 .f---~---.,.---..,_--_.,._--~ ~.4

0.0 0.2 0.4 0.6 0.8 1.0

Fig. I-Plot of vi' vs X for (x) alcohol - (I-x), 4-dioxane at 298.15 K (D ), 303. 15 K (X) 308. 15 K (0) and 313 .15 K (~) for methanol (- ), butanol ( -.-.-) and isobutanol (- --)

45r-----------------, 1.4

_ Scale ::.:::.-':::: --Scale __ 4.0

1.2

3.5

. 1.0 3.0

0. 8 c: u

~ 0.6

c: 2.5 u

~ 2.0

0.4

0.2 0.5

0.0 +---~--__r---,.__--~--_l. 0.0

0.0 0.2 04 0.6 0.8 1.0 x

Fig. 2-Plot of 1'] vs x for (x) alcohol - (I-x) 1,4-dioxane at 298.15 K (D ), 303 .15 K (X) 308.15 K (0) and 313.15 K (~) for meth anol (-), butanol ( -.- .-) and isobutanol (- - - ).

Absolute viscosities (1}) Viscosit ies of pure alcohols increase in the

followi ng order : MeOH < BuOH < iso-BuOH. Further viscosity of MeOH is less than the viscosity of D and although the values of viscosity of MeOH-D mixture lie in between these values, the slope is higher in D rich region (Fig. 2) . The value of TJ fo r D

is less than that of BuOH and iso-BuOH and the values of viscosities for mixtures containing BuOH and iso-BuOH are less than the values of D in the lower mole fraction region showing small minima in both the cases but the minimum in the case of BuOH­D system is slightly more prominent as compared to iso-BuOH-D system. At higher mole fraction region

0.0 ·,.-----------------., · 0.00

~.4

c: ~ -0.6 I="

-D.8

-1 .0 .

~.02

~.04

c: ~

~ ~.06

~.08

-1 .2 +----~--~--__,_--_.,.--__+ ~. 10

0.0 0.2 0.4 0.6 0.8 1.0 x

Fig. 3- Plot of T] E vs x for (x) alcoh~1 - (I-x) 1,4-dioxane at 298. 15 K (D ), 303 .15 K (X) 308.15 K (0) and 313.15 K (~) for methanol (- ), butanol ( -.- .-) and isobutanol (- - - ).

15.0 .. ~--------------_.. 0 --Scale __

10.0

5.0

0.0

'z E -5.0

. 0 §, -10.0

-L -15.0

-20.0

-25.0

-20

-40

· -60

-80 Z "e

-100 ~o

-120~ lr::

· -140

-1 60

-1 80

-30.0 -'--______________ ......1. -200

0.0 0.2 0.4 0.6 0.8 1.0

Fig. 4-Plot of K ssE vs x for (x) alcohol - ( I-x) 1,4-dioxane at 298.15 K (D ), 303. 15 K (X) 308.15 K (0) and 313. 15 K (~) for methanol (-), butanol (-.-.-) and isobutano,1 (- - -) .

the increase In the value of TJ for these mixtures IS much faster.

Excess viscosities (1}E)

From the plots of TJE vs x (Fig. 3) it may be seen that the values of TJ E are negative for all the three systems at all the four temperatures over the whole composition range. TJ E values decrease with increase in temperature in all the cases. Maximum magnitude of TJE values for mixtures containing various alcohols decreases in the order: iso-BuOH>BuOH>MeOH. Similar type of behaviour has also been reported by Sastry and Raj 22 for alcohols + methyl acrylate i.e. the negative magni tude of excess viscosities at equimolar

)

BANIPAL el at.: EXCESS FUNCTIONS OF BINARY MIXTURES OF ALCOHOLS & 1,4-DlOXANE 815

Table 4-Y aJues of the coefficients of Eq. 9 and standard deviation (0 ) for the (x) methanol-(l-x) I A-dioxane system

Temp A., A, A2 A3 0

IK, VE

293.15 -1.2311 -D.3520 -0.2428 -D.6622 0.0105

303. 15 - 1.1005 -D.5126 0.9457 -1.7174 0.0272

308. 15 -D.8290 -D.8837 1.0589 -1.3631 0.0224

313 .15 -D.638 I -D.8746 1. 7155 -2.3321 0.0290

TIE 298.15 - 0.3682 0.1550 -D.0036 -0.1702 0.0024

303. 15 -D.32 17 0.1224 -D.0720 -D.0714 0.0016

308.15 - 0.2858 0.0860 -0. 1425 0.0787 0.0020

313. 15 -0.2733 0.0754 -0.1224 0.0715 0.0009

KsE x 1012

298.15 -524.43 -236.16 - 167.18 -218.92 4.4379

303. 15 -560.72 -233.04 -159.80 -211.80 1.8590

308.15 -609.95 -258.8 1 - 174.91 -144.60 2.4694

313. 15 -640.13 -279.69 - 199.00 -55.367 2.5826

C E

298. 15 125 .642 -706.56 1741.90 - 11 33.0 1.5659

303 .15 45.5657 -231.37 855.255 -638.04 1.2790

308.15 -1 30.78 753.358 -983.90 420.142 1.7901

313.15 -126.60 546.609 -620.35 21 5.865 1.0020

Table 5-Yalues of the coefficients of Eq. 9 and standard deviation (0 ) for the (x) butanol- (I-x) I A-dioxane system

Temp A., A, A2 A3 0

K I

VE 298. 15 0.9379 -D.11I2 -D.1512 - 0.0651 0.0081

303. 15 1.0117 -D.0273 -0.0056 -D.2783 0.0047

308.15 1.0553 0.1598 0.2841 -0.4361 0.0067

313. 15 1.1458 0.1413 0.2884 -D.4216 0.0072

TIE 298.15 -2.4406 -D. 7268 -1 .0557 -0.4217 0.0061

303. 15 -1. 8980 -D.7568 -0.9448 -D.9192 0.0130

308. 15 -1.6666 -D.5793 -D.878 1 -D.7596 0.0079

3 13.15 -1.4413 -D.5245 -D.7055 -D.6507 0.0099

KsE x 10'2

298. 15 38.2043 - 24.780 -53.165 11.5022 1.0822

303.15 29.5728 - 199.75 311.838 -1 64.26 0.2940

308. 15 -50.566 24.6778 -22.41 2 - 29.924 0.6231

313 .15 -71.014 35.9858 - 61.075 3.9721 9 0.7534

C E

298.15 -945 .93 864.1 99 -739.18 -7 1.785 2.6 188

303 .15 -551.20 -468.09 1284.16 -1 398.9 5.2564

308.15 -625.36 - 752.59 -230 1.55 -2183 .9 3.448 1

3 13 .15 -699.61 -336.58 95 1.83 -1253.4 6.4470

816 INDIAN J CHEM, SEC. A, AUGUST 2000

Table 6-Values of the coefficients of Eq. 9 and standard deviation (0) for the (x)isobutanol-(I-x) I A-dioxane system

Temp Ao AI A2 A3 0

K

VE

298.15 0.9245 0.5541 --D.3631 --D.455 I 0.0093

303.15 1.0049 0.5516 --D.3624 --D.4960 0.0064

313.15 1.1834 0.6199 --D.083 I --D. 5 I 85 0.0050

llE

298.15 -2.6502 -9.4013 24.7111 -22.353 0.0326

303 .15 -2.8352 -3.8828 9.2147 -9.1685 0.0087

308.15 -2.6993 --D.7579 0.5034 -1.9292 0.0087

313.15 -2.5089 --D.1 219 0.9098 -2.4561 0.0067

K SEXlO12

298.15 -75.406 -9.1549

303.15 -78.943 16.0193

308.15 -96.395 17.4133

313.15 -103.66 20.1039

298. 15 -822.32 -1813.12

303.15 -986.36 -693.94

308. 15 -1076.9 322.836

313.15 -1210.9 930.034

compositions increase in the order : I-butanol > 1-propanol> methanol. From the plots it may also be observed that the minimum TI E values lie in the alcohol rich region for BuOH and iso-BuOH whereas in case of MeOH it lies in the D rich region and thus the minimum TI E values continuously shift towards alcohol rich region from MeOH to iso-BuOH.

Excess isentropic compressibilities (K/) From the plots of KSE vs x (Fig. 4) it may be seen

that the excess isentropic compressibilities are negative at all four temperatures for MeOH-D and iso-BuOH-D systems over the entire composition range, whereas for BuOH-D system the Ks E values are positive up to 0 .75 mole fraction and at higher mole fraction the values become almost zero at 298.1 5K. However, wi th increase in temperature Ks E values for this system al so become more and more negative and, at 308.15K and above the Ks E values are negative over the ent ire composi tion range having appreciable magnitude.

Enthalpy (MI *), entrophy (!!.S *) and free energy

(tl.G*j of activation oj viscous j7ow MI* values (Table 7) are positive for all the three

CE

48.4349 12.9530 0.7772

28.9318 -18.617 0.6183

7.79139 9.84470 0.9047

-32.237 23.5017 0.7675

6110.08 -4843.9 6.3642

3407.15 -2679.8 4.9286

'163.529 -701.64 4.6396

356.541 -785.87 4.6061

systems and M* values for the system containing MeOH and BuOH are positive but the magnitude is very small in the case of MeOH whereas both small

positive and negative values have been obtained for the iso-BuOH system. tl.G* values are positive for all the systems and the positive magnitude increases in the order : MeOH < BuOH < iso-BuOH.

Discussion To analyse the present results, excess enthalpy

(H E) values for methanol-I A-dioxane and ethanol-1 A-dioxane at 298. 15K have also been taken into accounts. Letcher and Govenders by comparing H E (x

= 0.5) values for alkanol + cyclohexane and . I h 6 23.24 cycloether + heptane WIth alkanol + cyc oet er . ,

have found that H E values fo r alkanol + cycloether are less endothermic than the sum of the H E values for the above corresponding systems. From this they concluded8 that three effects are contributi ng to the H E values of these mixtures : (i ) Positive contribution from the disruption of alcohol agglomerates, (ii ) Positive contribut ion from the disruption of ether­ether interaction, (i ii) Negative contribut ion from the ether-alcohol interaction.

In view of the above, first two steps will contribute

BANIPAL et at.: EXCESS FUNCTIONS OF BINARY MIXTURES OF ALCOHOLS & 1,4-DIOXANE 817

Table 7-Values of Mi* , M* a12ng with the values of t!.G* at 298.15K

XI Mi* M* t!.G* cal mol-I cal mol-I cal mOrl

Methanol-I, 4-Dioxane

0.0000 3916.66 2.09 3293.46

0.1044 4045.20 2.82 3203.69

0.2240 3821 .28 2.43 3096.61

0.31 92 3583.05 1.92 3009.48

0.3990 3496.29 1.85 2943 .36

0.5185 3334.82 1.66 2839.51

0.6073 3188.03 1.44 2758.91

0.7097 2995 .79 1.11 2664.92

0.8002 2889.69 1.04 2578.78

0.8935 2527,74 1.45 2484.55

1.0000 2257.86 -0.41 2379.77

Butanol-I A-Dioxane

0.0000 3916.66 2.09 3292.46

0.0943 3945.52 2.24 3276.57

0.1987 4194.14 3.07 3278.19

0.3037 4611.47 4.38 3304.67

0.4038 5258.16 6.42 3343 .63

0.4911 5564.55 7.32 3381.i7

0.5944 6015 .59 8.63 3441.10

0.6942 6272.48 9.26 3510.60

0.8085 6711.23 10.55 3594.56

0.9153 6911.97 10.75 3706.28

1.0000 6705.20 9.69 3815.41

Isobutanol -1 A-Dioxane

0.0000 3916.66 2.09 3292.46

0.0643 4088.99 2.70 3284.41

0.1276 4241.19 3.22 3280.82

0.3027 3791.43 1.58 3320.85

0.3993 3497.31 0.40 3376.71

0.4932 3350.92 -0.32 3446.54

0.5986 3828.80 0.91 3558.77

0.6991 3609.55 -0.1 5 3655.03

0.8020 3581.36 -0.61 3763.81

0.8980 3402.95 -0.16 3873.14 1.0000 42.67.83 0.76 4040.3 1

positively whereas the third will contribute negatively to the observed yE behaviour of these systems. In the case of MeOH-D system at 298.15K, the negative yE values may be attributed to the predominance of the third factor over the first two. Occurrence of positive yE in the D rich region indicates that D is more effective in breaking alcohol agglomerates 16,25.26

which suggests the predominance of first factor in

this region. Similarly in case of BuOH and iso-BuOH systems the positive V E values over the whole mole fraction range suggest that the positive contributions from the breaking up of alcohol agglomerates and ether-ether interactions are dominating over the negative contribution resulting from heteromolecular association8

. This may be attributed to the large size of BuOH and iso-BuOH than MeOH which will provide steric hindrance to heteromolecular association 16. This is further evident from large value of V E in the case of iso-BuOH than in the case of BuOH. V E values become more and more positive with increase in temperature in these two systems as in the case of MeOH-D system, but as ment ioned earlier the increase is less in the case of BuOH and iso-BuOH than in the case of MeOH, which suggests that the MeOH-D interactions are highly thermolabi Ie.

Mixtures with strong interactions between the molecules of the components show a maxima in the

viscosity as a function of composition and pOSitive value for the excess functions of viscosity, molar Gibbs free energy for activation of flow and the Grunberg and Nissan parameter25

,27.30. For the present studied systems (Fig. 2) there is smooth non-linear variation of the viscosity with the composition for MeOH-D system whereas in other cases small minima have been observed which suggests that no complex formation takes place or complexes of low stability are formed . This minimum can also be explained that D being spatial molecules hl:ive large volume31

, so at lower concentrations of BuOH and iso-BuOH, the alcohol molecules may find accommodation into the available spaces of D structure resulting in lower viscosity than the expected values. Similarly in the case of MeOH-D system higher slope observed in the D rich region can also be explained by the above reasoning. Comparing the behaviour of these systems it appears that the dispersion forces are dominating in BuOH and iso­BuOH than in the case of MeOH and this is in line with that observed from excess volume results. Further negative 11E values for all the systems are again indicati ve of the predominance of dispersion f 1612 d h' . . d f E f orces ' , an t e IncreasIng magllltu e 0 11 rom MeOH to BuOH to iso-BuOH suggests increase in dispersion forces in the same order.

CE values are positive with very smail magnitude for MeOH-D system and become negati ve in the case of BuOH and iso-BuOH and these results again

818 INDIAN J CHEM, SEC. A, AUGUST 2000

suggest that the complex with low stability may be fonned in the case of MeOH but dispersion forces are dominating in the case of BuOH and iso-BuOH. Negative d (Grunberg and Nissan parameter) values for all the systems, the magnitude of which increases from MeOH to iso-BuOH also indicate decrease in the strength of interactions from MeOH to iso-BuOH.

Negative Ks E values are generally observed when strong specific interactions among the components in the mixture are presentl. Therefore to explain negative KsE values for these systems except for BuOH system at 298.15K, other properties like HE, V E, llE discussed above should also be taken into account which have indicated the absence of any strong specific interactions . It has been reported33

•34

that in general V E and KSE have the same sign but observation contrary to this have also been made, e.g. in the case of n-hexane + 1 ,4-dioxane and chlorofonn + I ,4-dioxane systems. In the case of same sign of V E and KSE lack of proportionality between these

indicares that different types of interactions are operating in the mixtures l. Thus it appears from the present data that accommodation of one component in the environment of other is also playing a proininent role. Further it is known that values of V E and Ks E in binary mixtures are composed of three contributory tenns : (i) interactional, (ii) free volume and (iii) internal pressure I. For the systems studied presently it appears that both V E and Ks E are being affected by all these factors but to different extents. Comparison of Ks E values for these three systems suggest that interactions are stronger in the case of MeOH than BuOH and iso-BuOH. Differences in the values of Mi* and 6.5* (Table 7) are indicative of dominance of the dispersion forces 34 in system containing BuOH which may also be responsible for the positive and small negative values of KSE. !1G* values suggest that intennolecular interactions operating in these systems are decreasing from MeOH to BuOH to iso-BuOH. It may thus be concluded that these systems are being dominated by weaker interactions and dispers ion forces with the absence of any strong specific intennolecular interactions .

References I Oswal S L & Phalak R p. J sol Chern, 22 (1993) 43.

2 Deshpande D D & Oswal S L, J chern Soc. Faraday I , 68 (1972) 1059.

3 Oswal S L & Deshpande D D, Int data ser Sel data Sel' A, I (1988) 7.

4 Sharma S C, Lakhanpal M L & Rampaul M L. Indian J Chern, 21A (1982) 67.

5 Jain D V S, Wadi R K & Saini S B. J chern Thermodyn , 13 (1981) 903.

6 Inglese A, Wilhelm E, Grolier J -P E & Kehiaian H V, J chern Thermodyn, 12 (1980) 217.

7 GroJier 1 -P E. Inglese A & Wilhelm E, J chern Thermodyn , 16 (1984) 67.

8 Letcher T M & Govender U P, J chern eng Data, 40 (1995 ) J097.

9 Letcher T M & Domanska U, J chern ThemlOdyn, 26 (1994) 553.

10 Letcher T M, Domanska U & Govender U P, J chern Thermodyn, 26 (1994) 68 I.

I I Letcher T M, Domansk.'l U & Govender U P, J chern Thermodyn, 26 (1994) 1019.

12 Vogel A I, Textbook of practical organic chemistry, 3rd Ed (Longmans, London) 1957.

13 Riddick 1 A & Toops E E, Jr. , Organic solvents, (Interscience, New York) 1967.

14 Rattan V K, Singh S & Sethi BPS, Acustica, 64 (1987) 163 . 15 Picker P, Tremblay E & 1olicoeur C, J so! Chern, 3 (1974)

377. 16 Rattan V K. Sethi BPS, Singh S, Kaur H & Syngal M,

Acoust Lett, I I (1987) I In. 17 Rattan V K, Singh S, Sethi BPS & Wanchoo R K, Acoust

Lett. 10 (1986) 9. 18 Rattan V K, Singh S, Sethi BPS & Raju K S N, J chern

Thermodyn, 19 (1987) 35 . 19 Banipal T S & Sehgal G, Thermochim Acta, 262 (1995) 175. 20 Grunberg L & Nissan A H, Nature, 164 (1949) 799. 2 I Erdey-Gruz T, Transport phenomena in aqueous solutions,

(Adam Hilger, London), (1974). 22 Sastry N V & Raj M M, lndian J Chern A, 35 (1996) 49. 23 Nagata I & Kazuma K. J chern eng Data, 22 (1977)_79. 24 Dai M, Chao 1 P, Fluid Phase Equil, 23 (1985) 3 I 5. 25 Rattan V K, Sethi BPS, Singh S & Kaur H, Z Physik Chern

Neue Folge, 162 (1989) 47. 26 Blanco S T, Munoz Embid 1 & Otin S, J chern Thermodyn,

26 (1994) 23. 27 Fort R 1 & Moore W R, Trans Faraday Soc, 62 (1966) I I 12. 28 Rattan V K, Singh S, Sethi BPS & Bagga 0 p, Acustica, 64

(1987) 223 . 29 Assennor P & EIrich E R, J phys Chern, 72 (1968) 2910. 30 Solimo H N, RiggIo R, Derollo F & Katz M, Can J Chern, 53

( 1975) 1258. 31 Bilkis A B, Biswas S K & Al amgir M, Indian J Chern, 35A

(1996) 127. 32 Rattan V K, Singh S & Rajini M C, Indian J Techno!, 3 I

(1993)37 . 33 Poupko 1 P, Bull class Sci Acad Roy Beig , 4 1 (1955) 1009. 34 Reddy K C, Subrahmanyam S V & Bhimasenachar 1, J phys

Soc Japan, 19559.