J. Chem. Thermodynamics 1996, 28, 481–490

Speeds of sound and isentropic compressibilities of

(anisole + dichloromethane, or 1,2-dichloroethane,

or trichloroethene, or tetrachloroethene, or

cyclohexane); at T = 303.15 K

Jagan Nath

Chemistry Department, Gorakhpur University, Gorakhpur 273009, India

Measurements of speeds of sound, u, have been made in binary mixtures of anisole (C6H5OCH3)with dichloromethane (CH2Cl2), 1,2-dichloroethane (CH2ClCH2Cl), trichloroethene(CHClCCl2), tetrachloroethene (CCl2CCl2), and cyclohexane (c-C6H12) at T = 303.15 K.The densities r of the present mixtures have been calculated at T = 303.15 K using theavailable data on excess molar volumes VE

m, whereas the densities r* of the purecomponent liquids have been measured at T=303.15 K with a pyknometer, and these resultsare reported. Values of u have been used to calculate the apparent excess speeds of soundDu and the isentropic compressibilities kS for these mixtures. The excess isentropiccompressibilities kE

S , have also been calculated from the values of kS. The kES has been found

to be slightly positive for {xC6H5OCH3+(1−x)CH2ClCH2Cl}, and {xC6H5OCH3+(1−x)CCl2CCl2}, and slightly negative for {xC6H5OCH3+(1−x)CHClCCl2}. The kE

S is slightlypositive at low mole fractions of C6H5OCH3, and negative at high mole fractions of C6H5OCH3,for {xC6H5OCH3+(1−x)c-C6H12}. For {xC6H5OCH3+(1−x)CH2Cl2}, kE

S is very slightlypositive at low mole fractions of C6H5OCH3, and it shows a negative trend at high molefractions of C6H5OCH3. Values of kE

S for the various mixtures are discussed in the light ofintermolecular interactions between the components. 7 1996 Academic Press Limited

1. Introduction

Binary systems of anisole (C6H5OCH3) with tetrachloroethene (CCl2CCl2),trichloroethene (CHClCCl2), 1,2-dichloroethane (CH2ClCH2Cl), dichloromethane(CH2Cl2), and cyclohexane (c-C6H12) are of considerable interest from the viewpointof specific interactions leading to the formation of intermolecular complexesbetween the components in the liquid state. The specific interactions of C6H5OCH3

with CH2Cl2, CH2ClCH2Cl, CHClCCl2, and CCl2CCl2 can be thought of as beingdue to the presence of lone-pair electrons on the oxygen atom and an aromaticp-electron system in C6H5OCH3, due to which it can act as an np-donor towardthese chloro-compounds. The CH2Cl2, CH2ClCH2Cl, and CHClCCl2 can act ass-acceptors toward, and be involved in the formation of hydrogen bonds with,C6H5OCH3. The CCl2CCl2 can act as a s-acceptor toward C6H5OCH3. The system

0021–9614/96/050481+10 $18.00/0 7 1996 Academic Press Limited

J. Nath482

{xC6H5OCH3+(1−x)c-C6H12}, in which only non-specific forces can be consideredto be present between the components, can be used as a reference system. Further,there has been interest during recent years in the study of the binary systems(1–4) ofchloroalkanes and chloroalkenes of varying molecular complexity with other n- andp-donor components from the viewpoint of the existence of donor–acceptorinteractions between the components. It is known that, in the solid state, C6H5OCH3

forms a 1:1 complex(5–7) with TiCl4, and a 1:2 complex(8) with CCl4, and the valuesof excess dielectric constants(9) indicate that there exist specific interactions betweenthe components of the systems of C6H5OCH3 with CCl2CCl2, and CCl4. Nath andSrivastava(10) have measured excess volumes for {xC6H5OCH3+(1−x)CHClCCl2}.Nevertheless extensive studies concerning interactions between the components of thesystems of C6H5OCH3 with chloroalkanes and chloroalkenes of varying molecularcomplexity have not been carried out. Only recently, Nath and Chaudhary(11) andNath et al.(12) have made measurements of excess volumes, relative permittivities,refractive indices, dynamic viscosities and total pressures for binary systems ofC6H5OCH3 with CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2, and c-C6H12, andhave discussed the results in the light of the existence of donor–acceptor interactionsbetween the components. The values of the excess isentropic compressibilities kE

S (asobtained from the speeds of sound u in binary liquid mixtures) are known(13) to shedlight on the existence of specific interactions between the components. Hence, in thisprogramme, measurements of speeds of sound u have been made in binary liquidmixtures of C6H5OCH3 with CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2, andc-C6H12, and the results obtained are interpreted in this paper.

2. Experimental

The liquid components dichloromethane, 1,2-dichloroethane, trichloroethene,tetrachloroethene, cyclohexane, and anisole were purified and their purity was

TABLE 1. Densities r*, cubic expansion coefficients a*, isobaric molar heat capacities C*p,m, speeds of sound u*,isentropic compressibilities k*S , isothermal compressibilities k*T , and molar volumes V*m of pure liquids at T=303.15 K

compound r*g·cm−3

u*m·s−1

k*sTPa−1

k*TTPa−1

V*mcm3·mol−1

obs. lit.

103·aK−1

C*p,m

J·K−1·mol−1

CH2Cl2 1.3077420.00003 1.30777 a 1.377 d 101.24 e 1050.6 692.8 1061.5 64.946CH2ClCH2Cl 1.2383020.00003 1.23831 a 1.162 d 124.12 a 1175.5 584.4 847.9 79.916CHClCCl2 1.4514420.00003 1.4514 a 1.139 d 123.84 f 1015.0 668.8 956.3 90.523CCl2CCl2 1.6063720.00003 1.60640 a 1.025 d 142.31 a 1024.2 593.5 824.5 103.235c-C6H12 0.7692020.00002 0.76918 b 1.233 b 156.61 g 1230.6 858.5 1180.5 109.415C6H5OCH3 0.9846420.00002 0.98462 c 0.960 d 208.57 f 1387.3 527.7 674.8 109.828

a Reference 14. b Reference 15. c Reference 16. d Derived from densities in references 14 and 16. e Based onextrapolation of Cp,m data in reference 16. f See text matter of this paper; C*p,m for C6H5OCH3 is at T=304.75 K. g Basedon extrapolation of Cp,m data of references 16 and 17.

u and kS of binary mixtures of C6H5OCH3 483

TABLE 2. Speeds of sound u* and isentropic compressibilities k*S for the pure liquids C6H6, CHCl3,C6H5CH3, CCl4, (CH3)2CO, n-C6H14, and n-C7H16

liquid u*m·s−1

k*STPa−1

this literature this literature

TK

work value work value

C6H6 298.15 1299.0 1299.4 a 678.3 f 677.78 a

CHCl3 303.15 967.2 967.5 b 726.9 g 727 b

C6H5CH3 298.15 1306.2 1306 c 679.7 g 679.76 c

CCl4 298.15 921.0 921.11 d 744.1 f 743.92 d

(CH3)2CO 303.15 1144.8 1146 b 979.1 g 978n-C6H14 298.15 1077.0 1076.49 e 1316.6 g 1317.62 e

nC7H16 298.15 1129.8 1130.15 e 1153.0 g 1152.19 e

a Reference 18. b Reference 19; k*S is calculated from data on u* and r* reported in reference 19.c Reference 20. d Reference 17. e Reference 21. f Densities of C6H6 and CCl4 equal to 0.87367 g·cm−3 and1.58440 g·cm−3 respectively, as reported in reference 22, were used to calculate k*S . g Densities reportedin reference 14 and 16 were used to calculate k*S .

checked as described earlier.(11,12) The densities r* of the pure liquid components weremeasured using a single-capillary pyknometer (capacity about 25 cm3) made of Pyrexglass. The capillary had a 1-mm bore, and an etched mark around it near the topend which could be closed with an outside cap. All apparent masses were measuredwith an accuracy of (21×10−5) g with a K.Roy (model no. K-15 super) balance;corrections to mass were made. The values of r* with their estimated uncertaintiesare given in table 1. The speeds of sound u in pure liquids and their binary mixtureswere measured at a frequency of 3 MHz, using a quartz-crystal ultrasonicinterferometer (supplied by Mittal Enterprises, New Delhi, India). The quartz crystalwas fixed at the bottom of the measuring cell, and was excited at its resonantfrequency to produce sound waves of frequency of 3 MHz in the liquid in the cell,using a high frequency generator. A micrometer (supplied by MitutoyoManufacturing Company Ltd., Japan), which determined distances with an accuracyof 20.0001 cm, was provided at the top of the cell. It lowered or raised the metallicreflector plate (held parallel to the quartz crystal) through a known distance in theexperimental liquid, and thus the wavelength of the sound waves was determined bynoting the distance covered by the reflector plate between its positions at the timesof occurrence of the successive maxima of the anode current as shown by the currentmeter (microammeter) on the high frequency generator. The operation of theinterferometer was tested by measuring u in pure samples of C6H6, C6H5CH3, CCl4,CHCl3, (CH3)2CO, n-C6H14, and n-C7H16 at temperatures of T=298.15 K andT=303.15 K which were controlled with an accuracy of 20.01 K. The imprecisionin u is of the order of 20.5 m·s−1. Table 2 shows that the values of u and kS for theseliquids obtained in this work are in good agreement with those reported in theliterature.

J. Nath484

TABLE 3. Speeds of sound u, densities r, isentropic compressibilities kS, and the excess isentropiccompressibilities kE

S , for the various mixtures of C6H5OCH3 at T=303.15 K

xu

m·s−1r

g·cm−3kS

TPa−1kE

S

TPa−1

{xC6H5OCH3+(1−x)CH2Cl2}0.0228 1057.2 1.29536 690.7 1.270.0488 1066.2 1.28170 686.3 0.770.0726 1074.0 1.26960 682.8 1.090.1009 1083.9 1.25571 677.8 0.730.1352 1095.0 1.23956 672.8 1.560.1682 1106.4 1.22467 667.0 1.500.1875 1113.3 1.21624 663.4 1.320.2246 1127.4 1.20061 655.3 −0.100.2579 1138.8 1.18716 649.5 +0.120.2867 1149.0 1.17596 644.1 −0.060.3210 1161.0 1.16310 637.8 −0.120.3604 1174.8 1.14896 630.6 −0.200.4056 1190.6 1.13348 622.4 −0.240.4427 1203.5 1.12135 615.7 −0.300.4905 1220.2 1.10643 607.0 −0.550.5298 1233.0 1.09472 600.9 +0.160.5781 1249.8 1.08096 592.3 −0.180.6367 1269.0 1.06516 583.0 +0.340.6892 1287.0 1.05177 574.0 −0.070.7338 1302.0 1.04091 566.7 −0.280.8143 1328.4 1.02245 554.2 −0.320.9453 1369.9 0.99514 535.5 +0.18

{xC6H5OCH3+(1−x)CH2ClCH2Cl}0.0225 1179.6 1.23017 584.2 0.590.0569 1184.4 1.21806 585.2 2.840.0833 1189.3 1.20901 584.8 3.470.1270 1197.4 1.19448 583.9 4.450.1813 1207.2 1.17717 582.9 6.000.2154 1214.5 1.16669 581.1 5.910.2343 1218.0 1.16101 580.6 6.390.2778 1227.5 1.14825 578.0 6.120.3009 1231.0 1.14165 578.0 7.400.3329 1238.6 1.13269 575.5 6.700.3848 1247.4 1.11863 574.5 8.710.4116 1253.5 1.11157 572.6 8.380.4560 1262.4 1.10018 570.4 8.850.5624 1285.2 1.07429 563.6 8.580.5952 1291.4 1.06668 562.1 9.130.6130 1297.7 1.06261 558.8 6.930.6922 1314.3 1.04511 553.9 7.000.7293 1323.6 1.03720 550.3 5.730.7795 1335.6 1.02680 546.0 4.590.8409 1350.5 1.01450 540.5 2.940.8954 1363.5 1.00396 535.8 1.650.9362 1372.2 0.99628 533.1 1.48

{xC6H5OCH3+(1−x)CHClCCl2}0.0388 1027.2 1.42972 662.9 −2.020.0968 1045.8 1.39790 654.1 −4.480.1276 1056.0 1.38130 649.2 −5.800.1505 1063.2 1.36910 646.2 −6.05

u and kS of binary mixtures of C6H5OCH3 485

TABLE 3—continued

xu

m·s−1r

g·cm−3kS

TPa−1kE

S

TPa−1

0.1871 1075.8 1.34983 640.1 −7.600.2319 1090.2 1.32662 634.2 −7.730.2696 1104.0 1.30741 627.6 −9.320.2968 1112.4 1.29372 624.7 −8.510.3359 1126.8 1.27430 618.1 −9.690.3714 1139.3 1.25691 612.9 −9.890.4141 1155.0 1.23632 606.3 −10.360.4501 1167.0 1.21921 602.3 −9.090.4727 1176.0 1.20859 598.3 −9.770.5196 1193.4 1.18684 591.6 −9.510.5692 1212.0 1.16426 584.7 −8.970.5860 1218.0 1.15670 582.8 −8.320.6349 1237.7 1.13497 575.2 −8.510.6856 1257.0 1.11286 568.7 −7.260.7058 1266.0 1.10417 565.1 −7.770.7608 1286.4 1.08083 559.1 −5.320.8150 1309.5 1.05828 551.0 −5.090.8612 1327.4 1.03942 546.0 −2.990.8723 1333.0 1.03493 543.8 −3.480.9361 1359.5 1.00951 536.0 −1.48

{xC6H5OCH3+(1−x)CCl2CCl2}0.0398 1034.4 1.57952 591.7 −0.280.0928 1047.6 1.54414 590.1 0.310.1305 1056.3 1.51920 589.9 1.820.1858 1071.6 1.48296 587.2 1.810.2626 1092.0 1.43325 585.1 3.830.2686 1094.4 1.42939 584.1 3.160.3380 1114.8 1.38508 580.9 4.030.3487 1118.7 1.37830 579.7 3.480.3952 1132.8 1.34894 577.7 4.380.4398 1147.8 1.32099 574.6 4.170.4870 1163.4 1.29161 572.0 4.740.5528 1186.8 1.25099 567.5 4.810.6698 1231.5 1.17971 558.9 4.770.7699 1275.0 1.11964 549.4 2.980.8277 1302.0 1.08533 543.5 1.670.8737 1323.6 1.05822 539.4 1.270.9635 1368.6 1.00577 530.8 0.06

{xC6H5OCH3+(1−x)c-C6H12}0.0756 1232.4 0.78363 840.2 1.810.1179 1235.0 0.79193 827.9 1.200.2270 1242.4 0.81396 795.9 0.790.3319 1255.3 0.83586 759.2 −3.850.4060 1265.5 0.85166 733.2 −6.230.5071 1281.5 0.87358 697.0 −9.080.6076 1299.6 0.89569 661.0 −10.690.7440 1326.0 0.92613 614.1 −9.190.7891 1335.4 0.93629 598.9 −7.990.8317 1346.0 0.94594 583.5 −7.700.8750 1355.4 0.95581 569.5 −5.590.9354 1371.0 0.96967 548.7 −3.66

J. Nath486

3. Results and discussion

The speeds of sound, u*, in pure liquids CH2Cl2, CH2ClCH2Cl, CHClCCl2,CCl2CCl2, c-C6H12, and C6H5OCH3 at T=303.15 K are given in table 1, and valuesof u for mixtures of C6H5OCH3 with CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2,and c-C6H12 at T=303.15 K are reported in table 3. The present experimental valuesof u* in CCl2CCl2, CHClCCl2, CH2ClCH2Cl, CH2Cl2, and c-C6H12 at T=303.15 Kare (1024.2, 1015.0, 1175.5, 1050.6, and 1230.6) m·s−1 respectively, which are in goodagreement with the earlier(2,3) values of (1024, 1015, 1177, 1052, and 1232) m·s−1

respectively for the above liquids at T=303.15 K. The experimental values of u forthe various mixtures have been used to calculate the apparent excess speeds of soundDu (see figure 1) from the relation:

Du=u−Sxiu*i , (1)

FIGURE 1. Apparent excess speeds of sound Du plotted against x for the various mixturesat T = 303.15 K: W, {xC6H5OCH3 + (1 − x)CH2Cl2}; w, {xC6H5OCH3 +(1−x)CH2ClCH2Cl}; T, {xC6H5OCH3+(1−x)CHClCCl2}; r, {xC6H5OCH3+(1−x)CCl2CCl2}; q,{xC6H5OCH3+(1−x)c-C6H12}.

u and kS of binary mixtures of C6H5OCH3 487

where u*i refers to the speed of sound in the pure component i, and xi is the molefraction of i in the mixture. The Du has been fitted by the method of least squaresto the equation:

Du/m·s−1=x(1−x)sn

i=1

Ai (2x−1)i−1, (2)

where x is the mole fraction of C6H5OCH3. The values of the coefficients Ai ofequation (2), and the standard deviations d(Du) for the various mixtures are givenin table 4. The values of the isentropic compressibilities kS for mixtures of C6H5OCH3

with CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2, and c-C6H12, were obtained fromthe equation

kS=(VEm+V id

m )/(u2SxiMi ), (3)

using the excess molar volumes VEm reported earlier.(11) In equation (3), V id

m=SxiV*iis the molar volume corresponding to the ideal mixture, xi is the mole fraction ofthe component i in the mixture, and Mi is the molar mass of the component i. Thevalues of V*i of the pure components given in table 1 were used to estimate V id

m foruse in equation (3) for calculating kS. The values of the isentropic compressibilitiesk*S of the pure components CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2, c-C6H12,and C6H5OCH3 obtained from equation (3), by using r* of table 1, are reported intable 1, whereas those of kS for mixtures are given in table 3. The imprecision in kS

is of the order of 20.5 TPa−1. The imprecision in r is estimated to be of the orderof 22×10−5 g·cm−3. Also given in table 1 is the isothermal compressibility k*T forthe various pure liquids, which was calculated from the cubic expansion coefficienta, and the isobaric molar heat capacity Cp,m, using the equation:

kT=kS+a2VmT/Cp,m. (4)

The values of a and Cp,m, used to calculate k*T of pure liquids from equation (4), aregiven in table 1 with references. The value of Cp,m for C6H5OCH3, as reported inreference 14, is 208.57 J·K−1·mol−1 at T=304.75 K, which is used for the presentanalysis of kS at T=303.15 K. Normally, dC/p,m/dT is small for organic liquids, andthus its use may not affect the present conclusions. The value of Cp,m available(14) forCHClCCl2 is 122.59 J·K−1·mol−1 at T=293.15 K. The value of Cp,m for CHClCCl2,

TABLE 4. Values of the coefficients Ai of equation (2), and the standard deviations d(Du) for the variousmixtures at T=303.15 K

mixture A1 A2 A3 A4d(Du)m·s−1

{xC6H5OCH3+(1−x)CH2Cl2} 18.410 6.354 −24.110 26.115 0.45−37.435 7.280 6.239 8.547 0.72{xC6H5OCH3+(1−x)CH2ClCH2Cl}

{xC6H5OCH3+(1−x)CHClCCl2} −60.071 0.145 −3.743 −5.228 0.45{xC6H5OCH3+(1−x)CCl2CCl2} −153.199 −22.353 18.662 0.56{xC6H5OCH3+(1−x)c-C6H12} −116.271 20.179 −12.056 0.55

J. Nath488

estimated from the corresponding states method,(23) using C°p,m data reported by Stullet al.,(24) the acentric factor v, and the critical temperature Tc from reference 23, is125.42 J·K−1·mol−1 at T = 293.15 K, which is higher than the experimental value by2.83 J·K−1·mol−1. The Cp,m for CHClCCl2 estimated according to this method is126.67 J·K−1·mol−1 at T=303.15 K, and assuming it is also higher than theexperimental value by 2.83 J·K−1·mol−1, the value of Cp,m used in the present analysisis 123.84 J·K−1·mol−1, which is given in table 1.

The excess isentropic compressibilities kES given in table 3, were estimated from the

isentropic compressibilities kS of the mixtures using the relation:

kES =kS−kid

S , (5)

where kidS was obtained from the expression:(25,26)

kidS =(f1k*T,1+f2k*T,2)−{T(x1V*1 +x2V*2 )(f1a*1 +f2a*2 )2/(x1C*p,1+x2C*p,2)}

=f1{k*S,1+TV*1 (a*1 )2/(C*p,1)}+f2{k*S,2+TV*2 (a*2 )2/C*p,2}

−{T(x1V*1 +x2V*2 )(f1a*1 +f2a*2 )2/(x1C*p,1+x2C*p,2)}, (6)

where

fi=xiV*i /(x1V*1 +x2V*2 )=xiV*i /V idm , (7)

and V*i , k*T,i , a*i and C*p,i are the molar volume, isothermal compressibility, cubicexpansion coefficient, and molar isobaric heat capacity of the pure component i.

The kES for the various mixtures, obtained from equation (5), has been fitted by

the method of least-squares to the following equation:

kES /TPa−1=x(1−x)s

n

i=1

Bi (2x−1)i−1. (8)

The values of the coefficients Bi of equation (8), along with the standard deviationsd(kE

S ) are given in table 5.The values of kE

Smay be visualised in terms of strength of interactions operating

between the components of any given system. The negative values of kES for a given

system can be interpreted as due to a close approach of unlike molecules, leadingto a reduction in volume and compressibility. The different types of forces thatoperate between the components of given systems are: dispersion forces which shouldproduce a positive contribution to kE

S , and charge-transfer, hydrogen bonding,dipole-induced dipole and dipole-dipole interactions which should create negativecontributions to kE

S . Dispersion forces operate in all systems, and for a system inwhich more than one type of interaction is operative between the components, thekE

S values would be the net result of the contributions from all types of interaction.Table 3 shows that throughout the entire composition range, kE

S is positive for{xC6H5OCH3 + (1 − x)CH2ClCH2Cl}, and negative for {xC6H5OCH3 +(1 − x)CHClCCl2}, and is quite small in magnitude. For {xC6H5OCH3 +(1−x)CH2Cl2}, kE

S is very slightly positive at low concentrations of C6H5OCH3, andvery slightly negative (approaching practically zero) at high mole fractions of

u and kS of binary mixtures of C6H5OCH3 489

TABLE 5. Values of the coefficients Bi of equation (8), and the standard deviations d(kES ) for the various

mixtures at T=303.15 K

mixture B1 B2 B3 B4d(kE

S )TPa−1

{xC6H5OCH3+(1−x)CH2Cl2} −2.904 9.598 20.196 −32.146 0.56{xC6H5OCH3+(1−x)CH2ClCH2Cl} 33.822 −6.323 −5.100 −6.810 0.64{xC6H5OCH3+(1−x)CHClCCl2} −38.554 10.954 −1.223 6.585 0.44{xC6H5OCH3+(1−x)CCl2CCl2} 21.080 1.881 −23.023 0.55{xC6H5OCH3+(1−x)c-C6H12} −33.866 −46.453 24.854 0.58

C6H5OCH3. The kES is also very slightly positive for {xC6H5OCH3 +

(1−x)CCl2CCl2}. For {xC6H5OCH3+(1−x)c-C6H12}, kES is very slightly positive at

low concentrations of C6H5OCH3, and slightly negative at higher concentrations. Atx=0.5, kE

S for the various systems has the sequence:

CH2ClCH2ClqCCl2CCl2qCH2Cl2qc-C6H12qCHClCCl2.

The negative values of kES , along with the negative values(11) of VE

m and low positive(12)

values of excess molar Gibbs energies GEm for {xC6H5OCH3+(1−x)CHClCCl2},

indicate that there exist specific interactions between C6H5OCH3 and CHClCCl2 inthe liquid state. The GE

m is negative(12) for {xC6H5OCH3+(1−x)CH2Cl2}, whichindicates further the existence of specific interactions between C6H5OCH3 andCH2Cl2. The slightly positive values of kE

S at low mole fractions of C6H5OCH3, andvery slightly negative kE

S at its higher mole fractions, for {xC6H5OCH3 +(1−x)CH2Cl2}, may be visualised as being due to the predominance of thecontributions to kE

S from non-specific interactions over those due to specificinteractions between the components. The high positive values(12) of GE

m for{xC6H5OCH3 + (1−x)c-C6H12} and {xC6H5OCH3 + (1−x)CCl2CCl2} do notindicate the existence of any specific interaction between the components of these twosystems. The values of kE

S are positive for {xC6H5OCH3+(1−x)CCl2CCl2} which arein accord with the GE

m results for this system, indicating the non-existence of anyspecific interaction between the components. The VE

m is highly positive(11) for{xC6H5OCH3+(1−x)c-C6H12}, which is in accord with the GE

m results(12) for thissystem. The negative values of kE

S at higher mole fractions of C6H5OCH3 in thissystem may, however, be attributed to the predominance of contributions to kE

S dueto the dipole-induction forces between the components. The values of GE

m(12) and VE

m,(11)

which are low and positive for {xC6H5OCH3+(1−x)CH2ClCH2Cl}, may though betaken to indicate the likelihood of the presence of specific interaction between thecomponents. However, the positive value of kE

S for this system do not support thisviewpoint.

The author is grateful to the Head, Chemistry Department, Gorakhpur University,Gorakhpur, for providing laboratory facilities. Thanks are also due to the Councilof Scientific and Industrial Research, New Delhi (India), for financial support.

J. Nath490

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(Received 13 September 1995; in final form 22 November 1995)

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