856 J . Chem. Eng.

Data 1995,40, 856-861

Density, Viscosity, Refractive Index, and Speed of Sound in Aqueous

Mixtures of NJV-Dimethylformamide,Dimethyl Sulfoxide,
NJV-Dimethylacetamide,Acetonitrile, Ethylene Glycol, Diethylene
Glycol, 1,4-Dioxane,Tetrahydrofuran, 2-Methoxyethanol,and
2-Ethoxyethanol at 298.15 K
Tejraj M. Aminabhavi* and Bindu Gopalakrishna
Department of Chemistry, Karnatak University, Dhanvad 580 003, India

The density, viscosity, refractive index for the sodium D-line, and speed of sound in binary mixtures of
water with N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, acetonitrile, ethylene
glycol, diethylene glycol, 1,Cdioxane, tetrahydrofuran, 2-methoxyethanol, and 2-ethoxyethanol have been
determined at 298.15 K over the whole range of mixture compositions. From these results, the excess
molar volume, deviations in viscosity, speed of sound, molar refractivity, and isentropic compressibility
have been calculated. The computed results are fitted to the Redlich-Kister polynomial equation to
estimate the adjustable parameters and standard deviations. The observed negative VE values are
compared with the available literature results.

Introduction (all HPLC grade solvents from S. D. Fine Chemicals Ltd.),

and N,N-dimethylformamide and dimethyl sulfoxide (both
Liquid water is a unique solvent with its small size,
from Sisco Research Laboratories, Bombay) were used
quadrupole moment, and proton donor to acceptor ratio of
without further purification. A comparison of density and
1 and its ability to support extensive hydrogen-bonding
refractive index values of these liquids with the literature
networks. Innumerable studies have been made on aspects
findings, along with some important physical properties
of molecular interactions between water and polar organic
and mole percent purities of the solvents are given in Table
liquids (1-24). Such mixtures oRen show strong deviations
1
from ideality as regards density, viscosity, refractive index,
and speed of sound. Moreover, aqueous-organic mixtures Double-distilled deionized and degassed water with a
are encountered in a variety of areas, and a detailed specific conductance of 1 x Sam was used for the
understanding about their mixing behaviors is important measurements. The purity of the organic solvents was
from both practical and fundamental viewpoints. tested by GLC analyses using a flame ionization detector
Over the past decade, our group has been studying the (Nucon series, model 570015765, with fused silica columns)
thermodynamic and transport properties of binary organic having a sensitivity better than g of fatty acidlpL of
mixtures. Such data have applications in several design solvent.
and engineering processes. The present study is an exten- Binary mixtures were prepared by mixing appropriate
sion of our ongoing research program and presents experi- volumes of the liquid components in specially designed
mental values of density e, viscosity q, refractive index nD, ground glass air tight bottles and weighed in a single-pan
and speed of sound u for the binary mixtures of water with Mettler balance (Switzerland, model AE-240) to an ac-
N,N-dimethylformamide(DMF'),dimethyl sulfoxide (DMSO), curacy of fO.01 mg. The accuracy in mole fraction is
N,N-dimethylacetamide (DMAc),acetonitrile (AN),ethyl- +0.0001.
ene glycol (EG), diethylene glycol (DEG), 1,4-dioxane, Measurements. Densities of pure liquids and their
tetrahydrofuran (THF), 2-methoxyethanol (ME), and binary mixtures were measured using a pycnometer (Lur-
2-ethoxyethanol (EE) at 298.15 K over the whole range of ex, NJ) having a bulb volume of 10 cm3 and a capillary
mixture compositions. Such a comprehensive data ac- with an internal diameter of 1mm. An average of triplicate
cumulation of various properties on these mixtures is not measurements was considered, and these are accurate to
available in the earlier literature. From the basic physical i~O.0002g ~ m - ~ .
properties, excess molar volume VE, deviations in viscosity Viscosities were measured with a Cannon Fenske vis-
Aq, molar refractivity AR, speed of sound Au, and isen- cometer (size 100) supplied by the Industrial Research
tropic compressibility Aks have been calculated. These Glassware Ltd., NJ. An electronic stopwatch with an
results are discussed in terms of the molecular interactions accuracy of f 0 . 0 1 s was used to measure the flow times.
between water and organic molecules. Triplicate measurements of flow times were reproducible
within +0.01 s. Viscosities are accurate to fO.001 mPa.s.
Experimental Section Refractive index values for the sodium-D line were
Materials. The reagent grade 1,Cdioxane (E. Merck, measured with a thermostated Abbe refractometer (Bell-
Bombay), 2-methoxyethanol (Thomas Baker Chemicals, ingham and Stanley Ltd., London) with a precision of
Bombay), ethylene glycol (BDH, India), diethylene glycol f O . O O O 1 . Speed of sound data were obtained by using a
(S.D. Fine Chemicals Ltd., A.R. grade), tetrahydrofuran, variable path single-crystal interferometer (Mittal Enter-
2-ethoxyethanol, acetonitrile, and N,N-dimethylacetamide prises, New Delhi, model-M-841,using a cell of frequency
1MHz. These results are accurate to f 2 m-s-'. For water
To whom correspondence should be addressed at 298.15 K, the result of u of 1508 ms-' obtained in this
002 1-956819511740-0856$09.0010 0 1995 American Chemical Society
 Journal of Chemical and Engineering Data, Vol. 40, No. 4, 1995 867
Table 1. Comparison of Experimental Densities Q ) and Refractive Indices (nD)with Literature Values and Dipole
Moments and Molar Volumes of the Liquids at 298.16 K
liquid ~/(g.cm-~) nD
(mol % purity) exptl lit. exptl lit. P D Vo/(cm3.mol-1)
water (>99.8) 0.9973 0.9971 ( 2 ) 1.3314 1.3324 (30) 1.85 18.1
1,4-dioxane (>99.2) 1.0286 1.0280 (31) 1.4194 1.4167 (31) 0.00 85.7
THF (>99.2) 0.8823 0.8823 (19) 1.4052 1.4049 (31) 1.75 97.6
ME('99.3) 0.9604 0.9605 (32) 1.3995 1.4002 (33) 2.04 79.3
EE (>99.4) 0.9252 0.9251 (34) 1.4051 1.4057 (33) 2.08 97.4
EG (>99.1) 1.1003 1.1054 (35) 1.4166 1.4318b(33) 2.28 56.4
DEG (>99.2) 1.1135 1.1130 (9) 1.4447 1.4472b(33) 2.31 95.3
AN (>99.5) 0.7765 0.7765 (33) 1.3413 1.3416 (36) 3.53 52.9
DMAc ( ~ 9 9 . 1 ) 0.9366 0.9363 (33) 1.4356 1.4356 (33) 3.71 93.0
DMF(S99.2) 0.9445 0.9439 (33) 1.4275 1.4282 (33) 3.82 77.4
DMSO(299.3) 1.0960 1.0956 (37) 1.4769 1.4775 (33) 4.06 71.3

a References 33 and 38. These values are at 293.15 K.

study compares well with the value of 1502 m-s-l (24).
Experimental details of measurements of e, q, nD, and u
of liquids and liquid mixtures are the same as given earlier
(25). The isentropic compressibility k,, was calculated as
k, = l/u2e.
In all property measurements, an INSREF (model 016 where m is the number of data points and p is the number
AF') thermostat was used at a constant temperature control of estimated parameters. The results of A, and u are
of f O . O 1 K with a digital display which was calibrated with presented in Table 3.
the 1/10 thermometer (England make). Binary mixture Excess molar volume versus mole fraction plots are
data compiled in Table 2 are the averages of a t least three shown in Figure 1. For all mixtures, the values of VE are
independent measurements for each composition. negative, suggesting specific interactions between water
and the organic components of the mixture. The VE results
Results and Discussion of the mixtures follow the sequence DMAc < DMF < EE
The experimental values of density, viscosity, refractive < ME < DMSO < THF < 1,Cdioxane < DEG < AN < EG,
index, and speed of sound given in Table 2 are used to and the minima of the curves tend to shift toward the
calculate excess molar volume VE and the deviations in water-rich region of the mixtures. A large negative equimo-
viscosity Av, molar refractivity AR,speed of sound Au, and lar VE value of -1.537 cm3.mol-' is shown by the water +
isentropic compressibility Ak,, using the general equation +
DMAc mixture, whereas for the water EG mixture, the
equimolar VE of -0.224 cm3.mol-' is quite small. The large
AY = Y, - YICl - Y2C2 +
negative VE observed for the water DMAc mixture is the
result of a high dipole moment value 01 = 3.71 D) of DMAc
where AY refers to VE/(cm3.mol-l), Aq/(mPa.s), AR/ in addition to the difference in their sizes, leading to strong
(cm3mol-l), Au/(m*s-'), and Ak$TPa-l; Y, is the measured dipole-dipole interactions. Though the dielectric constant
mixture property under question and Yi refers to the of EG ( E = 37.7) is the same as that of DMAc ( E = 37.8),
respective property of the pure component of the mixture. +
the VE results of the water DMAc mixture are nearly 7
The terms C1 and Cz are mixture compositions expressed +
times higher than those of the water EG mixture. The
in mole fractions xi for the calculation of VE, Aq, and Au. observed values of the water +DMAc mixture when
The volume fractions @i are used for calculating AR and +
compared to the water EG mixture are attributed one
Ak,. The volume fraction was calculated as or both of the following effects (30): (i) the interactions
between hydroxy groups of ethylene glycol with water
molecules lead to weak dispersion type and/or hydrogen
bond effects, giving lower negative values, and (ii) the
1=1
presence of the amide group in dimethylacetamide leads
The values of AR were calculated from the Lorentz-Lorenz to higher specific interactions with water molecules because
equation (26,27)using the following equation for refractiv- of the presence of lone pair electrons on the nitrogen atom
ity R,: of dimethylacetamide, leading to higher negative VE values.
The difference in VE values between EG- and DEG-
Ri = [ ( n ~-, l)/(nD,'
~ + 2)1(Mj@,) (3) containing aqueous mixtures (i.e., VE is smaller for water
+ +
DEG than water EG mixtures) is also the result of
The calculated values of P, Aq, A??,Au, and Ak, were molecular size differences between the mixing organic
fitted to the Redlich-Kister (28) equation molecules and not the dipole moment or the dielectric
constant values. Almost identical values of VE observed
4 for mixtures of water with 1,4-dioxane or DEG presented
(4) in Figure 1 show similar types of interactions of these
organic molecules with water. For molecules like DMF (V
= 77.4 ~m~amo1-l) and ME (V = 79.2 cm3.mol-l), having
to estimate the adjustable parameters A, by the method of almost identical molar volumes, the values of VE are quite
nonlinear least squares using the Marquardt algorithm different; Le., for the latter mixture they are smaller than
(29).For none of the mixtures does the precision warrant for the former, suggesting higher specific interactions due
the use of more than five adjustable parameters. to the higher dipole moment value of DMF (p = 3.82 D)
The standard errors u between the calculated and than that of ME 01 = 2.04 D). Thus, in these mixtures,
experimental values were estimated using the VE values are more likely to be influenced by the
858 Journal of Chemical and Engineering Data, Vol. 40, No. 4, 1995

Table 2. Experimental Densities (p), Viscosities ( q ) ,Refractive Indices ( n ~ )and

, Speeds of Sound (u)of the Binary
Mixtures at 298.15 K
x1 g/(g.cm-3) t$(mPa.s) nD ul(ms-1) x1 ~/(g.cm-3) q/(mPa.s) nD ul(ms-1
+
Water (1) 2-Ethoxyethanol(2)
0.0000 0.9252 1.784 1.4051 1302 0.5995 0.9626 3.311 1.3974 1478
0.1100 0.9298 1.991 1.4044 1333 0.7033 0.9736 3.504 1.3925 1519
0.2089 0.9349 2.215 1.4036 1342 0.8037 0.9866 3.376 1.3838 1595
0.2940 0.9391 2.441 1.4031 1357 0.9020 0.9975 2.550 1.3674 1649
0.4058 0.9465 2.765 1.4017 1398 1.0000 0.9973 0.891 1.3314 1508
0.5043 0.9537 3.031 1.4000 1441
Water +
(1) 2-Methoxyethanol(2)
0.0000 0.9604 1.507 1.3995 1332 0.6002 0.9932 2.755 1.3901 1537
0.1049 0.9648 1.671 1.3985 1356 0.6964 1.0003 2.866 1.3852 1583
0.2062 0.9694 1.860 1.3977 1390 0.8004 1.0060 2.680 1.3762 1634
0.3055 0.9742 2.064 1.3966 1412 0.9005 1.0058 1.989 1.3598 1669
0.3977 0.9796 2.288 1.3953 1448 1.0000 0.9973 0.891 1.3314 1508
0.4976 0.9863 2.538 1.3933 1489
Water +
(1) Dimethyl Sulfoxide (2)
0.0000 1.0960 1.948 1.4769 1490 0.6065 1.0960 3.606 1.4425 1703
0.0958 1.0968 2.078 1.4730 1542 0.7032 1.0880 3.569 1.4297 1715
0.2097 1.0981 2.291 1.4772 1569 0.8053 1.0709 2.858 1.4079 1699
0.3132 1.0990 2.568 1.4646 1621 0.9021 1.0416 1.787 1.3774 1654
0.4090 1.0994 2.909 1.4590 1657 1.0000 0.9973 0.891 1.3314 1508
0.5030 1.0987 3.197 1.4524 1682
Water (1) + l,4-Dioxane (2)
0.0000 1.0286 1.172 1.4194 1363 0.6059 1.0369 1.797 1.3974 1483
0.1129 1.0300 1.222 1.4044 1367 0.6983 1.0372 1.913 1.3925 1529
0.2100 1.0310 1.291 1.4036 1371 0.8288 1.0333 1.857 1.3838 1572
0.3108 1.0325 1.384 1.4031 1378 0.9021 1.0248 1.570 1.3674 1554
0.4096 1.0342 1.510 1.4017 1392 1.0000 0.9973 0.891 1.3314 1508
0.4986 1.0356 1.629 1.4000 1437
Water (1)+ N,N-Dimethylformamide (2)
0.0000 0.9445 0.796 1.4275 1451 0.6057 0.9863 2.211 1.4128 1654
0.1056 0.9506 0.914 1.4267 1466 0.7015 0.9924 2.426 1.4045 1672
0.2069 0.9567 1.039 1.4253 1496 0.8044 0.9973 2.295 1.3903 1679
0.3030 0.9625 1.226 1.4239 1537 0.9034 0.9974 1.690 1.3675 1628
0.4062 0.9700 1.497 1.4217 1582 1.0000 0.9973 0.891 1.3314 1508
0.5088 0.9783 1.857 1.4165 1620
+
Water (1) Tetrahydrofuran (2)
0.0000 0.8823 0.481 1.4052 1289 0.6047 0.9288 1.129 1.3935 1371
0.1110 0.8876 0.515 1.4044 1292 0.7032 0.9426 1.394 1.3879 1427
0.1970 0.8928 0.565 1.4035 1294 0.8017 0.9597 1.651 1.3791 1481
0.3027 0.9001 0.650 1.4021 1302 0.9013 0.9803 1.665 1.3624 1581
0.4036 0.9082 0.763 1.4001 1319 1.0000 0.9973 0.891 1.3314 1508
0.5028 0.9175 0.916 1.3972 1339
Water (1)+ N,N-Dimethylacetamide (2)
0.0000 0.9366 0.920 1.4356 1458 0.6026 0.9831 3.310 1.4260 1662
0.1008 0.9423 1.071 1.4355 1483 0.7051 0.9923 3.873 1.4181 1693
0.2042 0.9490 1.286 1.4353 1514 0.8054 0.9981 3.612 1.4033 1696
0.3008 0.9558 1.582 1.4343 1551 0.9239 0.9980 2.342 1.3779 1684
0.4068 0.9648 2.047 1.4330 1592 1.0000 0.9973 0.891 1.3314 1508
0.5052 0.9740 2.607 1.4305 1620
+
Water (1) Acetonitrile (2)
0.0000 0.7765 0.361 1.3413 1283 0.6057 0.8678 0.656 1.3449 1380
0.1028 0.7865 0.375 1.3420 1282 0.6987 0.8918 0.750 1.3450 1425
0.2071 0.7987 0.402 1.3425 1297 0.7843 0.9182 0.842 1.3446 1500
0.2970 0.8109 0.436 1.3431 1311 0.8773 0.9522 0.940 1.3422 1538
0.4021 0.8270 0.495 1.3444 1332 1.oooo 0.9973 0.891 1.3314 1508
0.4985 0.8446 0.563 1.3447 1352
Water (1)+ Ethylene Glycol ( 2 )
0.0000 1.0003 9.408 1.4166 1688 0.6121 1.0733 3.968 1.3911 1700
0.1071 1.0977 8.625 1.4149 1705 0.7081 1.0629 3.112 1.3829 1684
0.2163 1.0947 7.631 1.4108 1708 0.8069 1.0479 2.263 1.3706 1641
0.3109 1.0912 6.731 1.4082 1706 0.9031 1.0275 1.524 1.3549 1598
0.3819 1.0883 6.068 1.4047 1712 1.0000 0.9973 0.891 1.3314 1508
0.5103 1.0811 4.919 1.3982 1711
Water (1) + Diethylene Glycol (2)
0.0000 1.1135 26.812 1.4447 1577 0.6157 1.1019 12.991 1.4237 1709
0.1041 1.1128 25.715 1.4432 1610 0.7095 1.0949 9.442 1.4139 1710
0.2105 1.1120 24.136 1.4409 1623 0.8250 1.0772 5.193 1.3975 1705
0.2697 1.1111 22.903 1.4396 1650 0.9059 1.0526 2.772 1.3761 1686
0.4009 1.1095 19.899 1.4355 1695 1.0000 0.9973 0.891 1.3314 1508
0.5145 1.1065 16.507 1.4299 1706
 Journal of Chemical and Engineering Data, Vol. 40, No. 4, 1995 859
Table 3. Estimated Parameters of Mixing Functions for Binary Mixtures at Different Temperatures
function Ao Ai AP A3 A4 U

+
Water (1) 2-Ethoxyethanol(2)
-4.115 2.301 -1.934 1.166 -0.151 0.015
6.738 -8.040 7.381 -2.113 -2.626 0.018
-27.569 21.476 -15.867 -21.289 -44.499 0.018
134.5 -283.3 -159.7 -1143.3 2277.3 4.651
-644.6 -133.6 243.8 1907.6 1426.6 11.09
+
Water (1) 2-Methoxyethanol(2)
-3.746 2.175 -1.119 -0.677 0.730 0.009
5.350 -6.428 4.758 0.873 -3.373 0.017
-19.559 13.303 -6.927 -2.144 -15.256 0.014
285.2 -414.7 324.5 -1115.4 1292.6 7.967
-576.18 70.40 -239.77 -332.18 -295.48 3.689
Water (1) + Dimethyl Sulfoxide (2)
-3.711 1.924 -0.040 -1.652 1.685 0.007
7.290 -10.234 4.255 9.830 -10.385 0.058
-19.803 11.092 -8.685 10.679 5.220 0.104
742.51 -503.63 42.63 -314.17 807.28 6.776
-415.47 175.83 -137.69 -138.12 -386.95 3.678
+
Water (1) 1,4-Dioxane (2)
-2.496 1.756 -0.703 0.204 -0.462 0.008
2.399 -3.769 3.583 -0.723 -1.471 0.012
-23.304 22.148 -6.773 -47.947 -80.978 0.211
-18.29 -611.45 739.80 142.65 -384.01 5.187
-360.99 237.07 221.73 -750.91 -242.94 4.654
Water (1) + Nfl-Dimethylformamide (2)
-4.489 1.857 0.002 -2.062 0.781 0.009
3.924 -7.569 5.397 3.669 -5.334 0.015
-20.173 13.208 -7.086 1.6989 -10.764 0.026
552.14 -636.86 278.74 -348.40 76.99 3.025
-468.2 42.86 -220.7 1372.5 1656.8 2.068
+
Water (1) Tetrahydrofuran (2)
-3.057 1.389 -0.837 1.757 -0.602 0.006
0.899 -2.642 3.763 -4.820 2.903 0.003
-20.876 13.918 -8.053 0.304 -13.373 0.005
-226.5 19.93 -68.9 -1119.1 1639.0 15.335
-381.8 -107.8 -238.7 -1364.5 -849.7 2.635
Water (1)+ Nfl-Dimethylacetamide (2)
-6.148 2.772 -0.016 -2.141 1.514 0.009
6.796 -13.969 11.874 3.853 -8.777 0.052
-27.568 21.703 -9.204 -3.845 -29.239 0.020
575.1 -510.7 125.4 -1050.8 1337.9 15.339
-486.25 206.43 -421.25 -406.58 -285.81 2.6466
+
Water (1) Acetonitrile (2)
-2.041 1.120 -0.637 1.379 -0.816 0.006
-0.243 -0.447 0.423 -0.919 0.944 0.004
-7.247 3.652 -1.598 0.348 -1.408 0.006
-187.07 -20.56 468.85 -936.83 285.73 6.895
-380.3 -572.1 -271.5 1833.5 2159.7 1.985
Water (1) + Ethylene Glycol (2)
-0.894 0.345 0.036 -0.160 0.088 0.006
-0.601 1.184 -0.692 1.726 1.699 0.009
-10.731 5.480 -2.969 1.893 -0.410 0.014
456.15 -285.43 -33.31 57.84 395.69 4.825
-153.86 92.20 57.91 -299.35 -403.47 1.258
Water (1)+ Diethylene Glycol (2)
-2.457 1.620 -0.717 -0.105 0.300 0.008
12.531 12.111 -13.195 4.328 3.591 0.050
-29.392 22.384 -13.830 -12.297 -37.014 0.012
668.5 -285.9 -300.8 -1023.8 1694.3 4.940
-325.90 -119.37 -134.75 980.58 666.64 3.437

differences in their dipole moment values than either their the VE results of these studies are in agreement with the
molar volumes or dielectric constants. present systems.
From a search of the literature, it is found that some of A comparison of the negative VE results of ME to those
the aqueous-organic mixtures studied here have also been of EG indicates that, for EG, the equimolar VE of -0.224
investigated by other researchers. A comparison of the few cm3mol-' is smaller than that observed for the water +
available literature VE results with the present values is ME mixture, for which VE is -1.001 cm3*mol-'. Thus, the
made in Table 4. The agreement between the present -OH group substitution in place of -OCH3 in the alkane
values and those of the literature results is generally good chain enhances the hydrophobic character of the cosolvent,
in almost all cases. Several researchers have studied the and this might reduce its ability to sustain any hydrogen-
VE results of water + n-alkoxyethanol mixtures (1-4), and bonding connectivity. This finding is also supported by
860 Journal of Chemical and Engineering Data, Vol. 40, No. 4, 1995
0 0

3.2

-0 4 -0 4
-
'_
2.L

t
-0 8 .
CL
E 1.6

08
-1 2 -1 2
0

-1 6 -0 8 ' ' 1.0 8

0 02 O L 0 6 0 8 1 0 0 2 0 1 0 6 0 8 1 0 0 2 0 4 0 6 0 8 1 0 0 2 O L 0 6 0 8 1

X1
1
Figure 2. Deviations in viscosity versus the mole fraction of water
Figure 1. Excess molar volume versus the mole fraction of water for the water-organic mixtures given in Figure 1.
for aqueous mixtures of (0)l,4-dioxane, ( 0 )DMF, ( 0 )THF, ( A )
DMAc, (e)AN, (A)DMSO, (M) EG, (v)DEG, ( 0 )EE, and (VI ME
a t 298.15 K.
180
Table 4. Comparison of Excess Molar Volumes around
the Equimolar Composition of the Mixtures at 298.15 K 120

water with x1 obsd lit. 60

2-ethoxyethanol 0.5979 -1.118 -1.084 (3)

0.4583 -0.977 -0.976 (4) 0
2-methoxyethanol 0.6454 -1.019 -1.379 (3)
0.5223
0.4999
0.4833
-0.958
-0.936
-0.918
-0.822
-0.932
-0.910
(1)
(2)
(4)
-60 0J 0 2 01, 0 6 0 8 1
0 0 2 0 4 0 6 08 1
-60

dimethyl sulfoxide 0.5000 -0.928 -0.928 (17) *I

0.5202 -0.946 -0.956 (39) Figure 3. Deviations in the speed of sound versus the mole
1,4-dioxane 0.4910 -0.616 -0.610 (18)
fraction of water for the water-organic mixtures given in Figure
tetrahydrofuran 0.5460 -0.792 -0.998 (19)
1.
Nfl-dimethylacetamide 0.5000 -1.537 -1.579 (17)
acetonitrile 0.4982 -0.509 -0.625 (15)
ethylene glycol 0.4732 -0.218 -0.325 (13) water are attributed to the fact that, due to the presence
0.5022 -0.224 -0.335 (4) of the third methyl group in DMAc, the molecule becomes
diethylene glycol 0.4372 -0.557 -0.579 (9) more polar than DMF, thereby increasing its hydrogen-
Nfl-dimethylformamide 0.5000 -1.122 -1.134 (17) bonding ability and thus giving more negative VE in the
+
water DMAc mixture than in the water DMF mixture. +
other papers in the literature (2, 5 ) . The more negative +
Densities of water AN mixtures have been measured
+
VE observed for the water ME mixture compared to that in the temperature interval of 278.15-318.15 K(18).The
+
for water EG could originate from two effects: the lower calculated VE results of this study are in good agreement
cohesive energy of ME and the enhanced water-ME with the present data. Also, the VE and Ak, results of the
interactions relative to water-EG interactions. This is also +
water THF mixture from the literature (19,20) are in
supported by the published HE,GE,and TSEresults of these good agreement with the present data. A number of
mixtures (2). studies have been made at 298.15 K on the volumetric
The magnitude of the minimum value of VE observed in +
properties of 1,4-dioxane water systems (21-24). The
+
the case of water ME is approximately 4 times larger calculated results of VE from these studies also agree with
+
than that observed in water EG mixtures. Other studies the present VE values.
+
in the literature ( 4 , 6, 7) on water ME mixtures agree The values of A7 presented in Figure 2 are positive for
all the mixtures except at a few compositions in the case
with the literature data as well as with our present values.
Intramolecular hydrogen-bonding in alkoxy alcohols stud- of mixtures of water with EG, DEG, or AN. With these
ied by infrared spectral studies (8)indicated that they are mixtures, the values of A7 are both positive and negative
relatively unstructured liquids having strong but not and the magnitudes of A7 are small when compared to
specific dipole-dipole interactions. Thus, in mixtures of those of other binaries. The results of A7 vary according
ME or EE with water, the effects contributing t o negative to the sequence DEG > DMAc > DMSO > EE > ME >
VE are due to disruption of (i) intramolecular hydrogen DMF > 1,4-dioxane > THF > AN > EG. The A7 versus x1
curves for a majority of the mixtures shift toward the
bonds and intramolecular dipolar interactions in ME or EE
water-rich region, an observation that is similar to the VE
and (ii) the hydrogen bonds present in the self-associated
results.
water molecules. Density results of the mixtures of aque- The results of Au versus x1 presented in Figure 3 are
ous ethylene glycol over a range of temperatures (9-13) positive for all mixtures except those of water with THF,
and of diethylene glycol as well as higher glycols at 298.15 AN, or 1,Cdioxane. Moreover, for mixtures of water with
K (14-16)have been presented. Our present results agree AN, 1,4-dioxane,THF, ME, or EE, the variation of Au with
with these findings. x1 shows sigmoidal curves, and the values of Au for water
In a study by Gomaa (17), the trend in the variation of + + +
AN, 1,4-dioxane, THF, or EE mixtures are both +
VE is DMAc < DMF < DMSO for aqueous mixtures of positive and negative. On the other hand, the results of
DMAc, DMF, and DMSO, which is similar to that of the Ak, displayed in Figure 4 are negative for all the mixtures,
present study. It may be noted that though DMF and and these values change according to the sequence EE <
DMAc have almost identical sizes, their interactions with ME < DMAc < DMF < THF < DMSO < AN < 1,4-dioxane
 Journal of 'Chemical and Engineering Data, Vol. 40, No. 4, 1995 881
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the maxima of VE and AR values for this mixture for
instance, as well as for other mixtures, are in fact located Received for review November 21,1994. Accepted March 31,1995."
at the same point. Furthermore, the AR values for
JE940250T
mixtures of water with DMF or ME vary with 41 almost
identically throughout the composition scale of the mix-
tures. Abstract published in Advance ACS Abstracts, June 1, 1995.
~3