J. Chem. Thermodynamics 1996, 28, 167–170

Speeds of sound and isentropic compressibilities

of {xC2H5OC2H5+(1−x)C6H6} and

{xC2H5OC2H5+(1−x)CCl4} at T=298.15 K

Jagan Nath

Chemistry Department, Gorakhpur University, Gorakhpur 273009, India

Speeds of sound u of {xC2H5OC2H5+(1−x)C6H6} and {xC2H5OC2H5+(1−x)CCl4} havebeen measured at T=298.15 K. Values of u have been used to calculate the isentropiccompressibilities kS for these mixtures. The values of the excess isentropic compressibilities kE

S

have also been calculated and are found to be negative throughout the entire range of x. Thequantity Du, which refers to the deviations of the experimental values of u from those obtainedfrom a mixture law, has also been calculated. 7 1996 Academic Press Limited

1. Introduction

The excess molar volumes VEm and excess molar enthalpies HE

m of {xC2H5OC2H5+(1−x)C6H6} and {xC2H5OC2H5+(1−x)CCl4} have been reported earlier.(1)

In the present research, measurements of the speed of sound u have been made forthese mixtures at the temperature T=298.15 K, and the results are reported in thispaper. These measurements have been undertaken in order to gain insight intospecific interactions of C2H5OC2H5 (diethyl ether) with C6H6 (benzene) and CCl4(tetrachloromethane) in the liquid state.

2. Experimental

Liquid C6H6, CCl4, and C2H5OC2H5 all of AR quality, were subjected to furtherpurification by standard methods.(2) The densities r* of the pure liquids are given intable 1. The speeds of sound u were measured at T=(298.1520.01) K and at afrequency of 3 MHz, using an ultrasonic interferometer. The precision in u is of theorder of 20.5 m·s−1.

3. Results and discussion

The speeds of sound u for pure C6H6, CCl4, and C2H5OC2H5 at T=298.15 K are givenin table 1, and u for {xC2H5OC2H5+(1−x)C6H6} and {xC2H5OC2H5+(1−x)CCl4} is given in table 2. Table 2 also contains the values of the isentropic

0021–9614/96/020167+04 $18.00/0 7 1996 Academic Press Limited

J. Nath168

compressibilities kS for {xC2H5OC2H5 + (1−x)C6H6} and {xC2H5OC2H5 +(1−x)CCl4}, obtained from the equation:

kS=(VEm+V id

m)/(u2·SixiMi ), (1)

using the excess volumes VEm reported earlier.(1) In equation (1), V id

m=SixiV*m, i is themolar volume corresponding to the ideal mixture, xi is the mole fraction ofcomponent i in the mixture, and Mi is the molar mass of component i. The valuesof the molar volumes V*m of the pure components given in table 1 were used toestimate V id

m for use in equation (1) for calculating kS . The values of the isentropiccompressibilities k*S of the pure components C6H6, CCl4, and C2H5OC2H5 arereported in table 1, and kS for the mixtures are given in table 2. The precision in kS

is of the order of 20.5 TPa−1. The densities calculated from VEm measurements(1) for

the present mixtures are also given in table 2. Also given in table 1 are the isothermalcompressibilities k*T for C6H6, CCl4, and C2H5OC2H5, which were calculated from theisobaric thermal expansivities a*p and the isobaric molar heat capacities C*p, m, usingthe equation:

kT=kS+a2pVmT/Cp, m. (2)

The values of ap and Cp, m given in table 1 were used to calculate kT fromequation (2). The values of Du for {xC2H5OC2H5 + (1−x)C6H6} and{xC2H5OC2H5+(1−x)CCl4} were calculated from the speeds of sound u of themixtures, using the relation:

Du=u−Sixiu*i , (3)

where u*i refers to the speed of sound of the pure component i. The excess isentropiccompressibility kE

S given in table 2 was estimated from the isentropic compressibilitykS of the mixture using the relation:

kES =kS−kid

S , (4)

TABLE 1. Densities r*, isobaric thermal expansivities a*p , 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 component liquids at

T=298.15 K

Component r*g·cm−3

103·a*pK−1

C*pJ·K−1·mol−1

u*m·s−1

k*STPa−1

k*TTPa−1

V*mcm3·mol−1

Obs. Lit.

C6H6 0.87367 0.87365(3) 1.218(4) 135.74(3) 1299.0 678.3 969.6 89.410CCl4 1.58440 1.58435(3) 1.228(4) 131.35(3) 921.0 744.1 1076.4 97.086C2H5OC2H5 0.70764 0.70760(2) 1.617 (a) 171.61 (b) 978.6 1475.6 1951.4 104.748

a Derived from densities in reference 5.b Obtained by extrapolation of Cp, m values in reference 5.

u and ks for {xC2H5OC2H5+(1−x)C6H6 or CCl4} 169

TABLE 2. Speeds of sound u, densities r, isentropic compressibilities kS , and the excess isentropiccompressibilities kE

S at T=298.15 K

xu

m·s−1r

g·cm−3kS

TPa−1kE

S

TPa−1

{xC2H5OC2H5+(1−x)C6H6}0.0316 1287.6 0.868117 694.8 −13.370.0677 1276.2 0.861781 712.5 −29.450.0907 1268.4 0.857751 724.6 −38.620.1394 1252.2 0.849242 751.0 −56.650.1634 1244.4 0.845063 764.2 −65.000.1881 1236.0 0.840773 778.5 −72.730.2161 1227.0 0.835925 794.6 −81.290.2398 1218.6 0.831834 809.5 −87.110.2788 1206.0 0.825131 833.3 −96.950.3109 1195.8 0.819641 853.2 −104.420.3437 1185.6 0.814057 873.9 −111.310.3780 1174.2 0.808248 897.4 −116.400.3999 1167.6 0.804556 911.7 −120.060.4504 1152.0 0.796088 946.5 −126.320.4711 1144.8 0.792637 962.6 −126.790.5161 1131.0 0.785174 995.7 −129.420.5594 1117.2 0.778040 1029.8 −129.090.5912 1107.0 0.772832 1055.9 −127.420.6220 1097.4 0.767811 1081.5 −125.270.6561 1086.6 0.762278 1111.0 −121.470.6833 1077.6 0.757883 1136.3 −116.420.7323 1062.6 0.750005 1180.9 −107.930.7754 1048.8 0.743115 1223.4 −96.630.8003 1041.0 0.739149 1248.4 −89.450.8350 1030.2 0.733639 1284.3 −78.150.8807 1015.8 0.726409 1334.1 −60.290.9305 1000.2 0.718559 1391.1 −37.580.9744 986.4 0.711659 1444.2 −14.21

{xC2H5OC2H5+(1−x)CCl4}0.0309 920.8 1.556184 757.9 −10.600.0877 920.6 1.504537 784.3 −28.770.1310 920.8 1.465337 804.9 −41.870.2107 921.6 1.393540 844.9 −63.230.2390 922.2 1.368151 859.4 −70.340.2710 922.8 1.339502 876.7 −77.370.2997 923.4 1.313865 892.6 −83.180.3358 924.6 1.281690 912.7 −90.170.3640 925.2 1.256614 929.7 −94.320.3929 926.4 1.230967 946.6 −98.930.4244 927.6 1.203074 966.0 −102.880.4692 928.8 1.163517 996.3 −105.580.4920 930.0 1.143436 1011.2 −107.360.5196 931.2 1.119178 1030.4 −108.260.5686 933.6 1.076245 1066.0 −108.180.6053 936.0 1.044209 1093.1 −107.530.6411 938.4 1.013060 1121.0 −105.300.6763 940.8 0.982539 1149.9 −101.430.6996 942.6 0.962395 1169.5 −98.340.7477 946.8 0.920967 1211.3 −90.520.7825 949.8 0.891132 1243.9 −82.290.8192 954.0 0.859801 1277.9 −73.840.8413 956.4 0.841002 1299.9 −67.150.8902 962.4 0.799595 1350.3 −50.440.9535 970.8 0.746404 1421.6 −22.470.9709 973.8 0.731868 1440.9 −14.99

J. Nath170

TABLE 3. Values of parameters in equation (5)

Y A1 A2 A3 A4 d

{xC2H5OC2H5+(1−x)C6H6 }Du/(m·s−1) −10.97 7.33 −10.23 0.31kE

S /TPa−1 −515.91 −70.80 −1.53 4.37 0.51

{xC2H5OC2H5+(1−x)CCl4 }Du/(m·s−1) −77.45 −23.25 −13.64 0.18kE

S /TPa−1 −431.63 −92.36 −8.22 1.02 0.48

where kidS was obtained as outlined in references 6 and 7. Both Du and kE

S were fittedby the method of least squares to the equation:

Y=x(1−x)· sn

i=1

Ai (2x−1)i−1. (5)

where Y is Du/(m·s−1) or kES /TPa−1. The values of the coefficients Ai of equation (5)

and the standard deviations d are given in table 3.The values of kE

S can be discussed in terms of the strength of interactions betweenthe components of any given system. The negative values of kE

S of a given systemcan be interpreted as due to a closer approach of unlike molecules, leading to areduction in volume and compressibility. The present results show that kE

S is highlynegative for {xC2H5OC2H5+(1−x)C6H6} and {xC2H5OC2H5+(1−x)CCl4}, whichindicates the existence of strong intermolecular interaction between the componentsof these systems.

The author gratefully acknowledges the financial support received from the Councilof Scientific and Industrial Research, New Delhi, India.

REFERENCES

1. Rastogi, R. P.; Nath, J.; Yadava, R. B. Indian J. Chem. 1970, 8, 541–543.2. Riddick, J. A.; Bunger, W. B. Techniques of Chemistry, Vol. II. Organic Solvents; Physical Properties

and Methods of Purification, 3rd edition. Weissberger, A.: editor. Wiley: New York. 1970.3. Tamura, K.; Ohomuro, K.; Murakami, S. J. Chem. Thermodynamics 1983, 15, 859–868.4. Kiyohara, O.; Halpin, C. J.; Benson, G. C. J. Chem. Thermodynamics 1978, 10, 721–730.5. Timmermans, J. Physico-Chemical Constants of Pure Organic Compounds. Elsevier: Amsterdam. 1950.6. Benson, G. C.; Kiyohara, O. J. Chem. Thermodynamics 1979, 11, 1061–1064.7. Handa, Y. P.; Halpin, C. J.; Benson, G. C. J. Chem. Thermodynamics 1981, 13, 875–886.

(Received 25 July 1995; in final form 18 September 1995)

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