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The thermodynamic properties of carbon disulphide + benzene and carbon disulphide + hexafluorobenzene
M-907(N) J. Chem. Thermodynamics 1978, 10, 1205-1207
Note The thermodynamic properties of carbon disulphide and carbon disulphide + hexafluorobenzene R. J. HILL,
E. O’KANE,
+ benzene
and F. L. SWINTON”
School of Physical Sciences,New University of Ulster, Coleraine,N. Ireland, U.K. (Received30 March 1978)
A few years ago, in a paper concerning the ability of hexafluorobenzene (C,F,) to form solid molecular compounds with a variety of other substances, Ott et al.(‘) noted that carbon disulphide (CS,) was the only non-cyclic molecule for which there was evidence of compound formation with C,F,. No additional information was given and, as we have commenced a detailed study of binary mixtures containing CS2, it seemed of interest to produce a complete phase diagram. In addition the excess molar volume VE was measured for this mixture and for the related mixture carbon disulphide + benzene at 298.15 K. The purity of all three substances was in excess of 99.9 moles per cent. The purification techniques and the experimental methods have been given previously.(244’ The phase diagram for {xCS, + (1 -x)C6F6} is given in figure 1. The existence of an
170 -0
A-A-Ad-A-A-A-A-Al I 0.2 0.4
I 0.6
FIGURE 1. The phase diagram for {xC$+(l-x)CaFB}. A, eutectic. a To whom correspondence should be addressed. 0021-9614/78/121205+03 $01.00/O
A-A-A-A-
4 I 0.8
0, Freezing
I curve; n , peritectic;
0 1978 Academic Press Inc. (London)
Ltd.
1206
NOTE
incongruently melting compound of composition 2&F, =CS, was identified by measuring the lengths of the arrest times at the peritectic temperature, 266.1 K. One notable feature of figure 1 is the extremely small slope of the freezing curve over a wide range of composition. This is evidence of large positive deviations from ideality and leads to a eutectic composition xr(CS,) > 0.99 and a eutectic temperature indistinguishable from the freezing temperature of pure CS,. In this respect the phase diagram closely resembles that for carbon disulphide + 1,5-hexadiyne.(” The excess molar volumes for (xCS, + (1 -x&H,) and {xCS, +(I -x)CgF6} at 298.15 K are tabulated in table 1 as a function of X. Also given are the deviations SVE calculated from the smoothing equation : SV,” = V,E(expl)-x(1 -x)(&+ Vi(l-2x)+ V,(1-2~)~). (1) The coefficients V,, V,, and I’, are given in table 2 together with the standard deviations o(Vz) and the smoothed values of Vz(x = 0.5). TABLE
1. Excess
molar
v:
volume Vz for {xC&+(l -x)C,X,} at 298.15 6 Vz calculated from equation (1) and table 2
1oViv:
x
cm3 mol-1
cm3 mol-’
0.2720 0.3224 0.4151 0.4842 0.5022
0.4000 0.4483 0.5041 0.5213 0.5272
-27 +19
+I6
0.2948 0.3807 0.3897 0.4139 0.4336
1.680 1.975 2.007 2.050 2.068
x
-
104&v: .~-v,“cm3 mol - 1 cm3 mol - 1
K and
the deviations
lO%P -.111-m-VE cm3 mol - 1 cm3 mol - 1
x
CsHs
-21 +13
0.5154 0.5536 0.6082 0.6293 0.6506
0.5230 0.5279 0.5149 0.5056 0.4949
-15 +5 +14 +17 -19
0.4401 0.5220 0.5399 0.6084 0.7129
2.123 2.199 2.192 2.178 1.948
-39 120 -t8 -6 -13
0.6587 0.7080 0.7624
0.4930 0.4584 0.4090
$11 -7 -5
+24
0.7157 0.7458 0.7614 0.8325
1.920 1.832 1.748 1.430
-23 -4 -25 +19
C.&i
TABLE
csxs C&s GF,
2. Smoothing
coefficients ___- VO cm3 mol-’ 2.1025 8.7036
and standard --__ VI cm3 moI-l -0.2205 --I .6379
+9 -3 +12 -3
deviations
for {xCSz+(l
Vi? cm3 mol-’ 0.1533 0.7363
-x)CGXB} ~-104(Vo,E) cm3 mol - 1 21 179
at 298.15
K
V,“(x = 0.5) cm3 mol-’ 0.526 2.176
There appear to be no previous measurements on these systems with which to compare the present results. Both VE curves are slightly skewed towards high mole fractions of CS, with maxima at x = 0.528 and x = 0.550 for {xCS, +(I -x)C,H,} and {xCS, + (1 -x)&F,}. By ,coincidence V,” for (xCS, + (1 -x)CsHs} is virtually identical to that for {xCS, + (1 -x)c-C,H,,} at the same temperature.‘2’ There is a similar close similarity between I/ z for {xCS, +(I -x)&F,} and that for
NOTE
1207
{xC,H,,+(~ -x)C,F,}. (5) This latter mixture also exhibits incongruently melting solid compounds and the large positive VE’s are evidence of weak unlike intermolecular interactions and large positive deviations from ideality.‘6, ‘) R.J.H. gratefully acknowledges the award of a N.I. Department of Education Postgraduate Studentship and the authors would like to thank the S.R.C. for the provision of essential equipment. REFERENCES !. Ott, J. B.; Goates, J. R.; Reeder, J.; Shirts, R. B. J. CZxm. Sm. Faraday Trans. Z 1974,70, 1325. 2. Hill, R. J.; O’Kane, E.; Swinton, F. L. J. Chem. Thermodynamics 1978, 10, 1153. 3. Brennan. J. S.: Hill. R. J.: Swinton. F. L. J. Chem. Thermodvnamics 1978. 10. 169. 4. Brennan; J. S.; Brown, N. M. D.; Swinton, F. L. J. Chem. So;. Faraday Tt&s: Z 1974,70, 1965. 5. Duncan, W. A.; Sheridan, J. P.; Swinton, F. L. Trans. Faraday Sot. 1966, 62, 1090. 6. Swinton, F. L. In Molecular Complexes, Vol. 2, R. Foster: editor. Elek Science: London. 1974, p. 63. 7. Swinton, F. L. In Chemical Thermodynamics, Vol. 2, M. L. McGlashan: editor. Chem. SOL: London. 1978.
Note The thermodynamic properties of carbon disulphide and carbon disulphide + hexafluorobenzene R. J. HILL,
E. O’KANE,
+ benzene
and F. L. SWINTON”
School of Physical Sciences,New University of Ulster, Coleraine,N. Ireland, U.K. (Received30 March 1978)
A few years ago, in a paper concerning the ability of hexafluorobenzene (C,F,) to form solid molecular compounds with a variety of other substances, Ott et al.(‘) noted that carbon disulphide (CS,) was the only non-cyclic molecule for which there was evidence of compound formation with C,F,. No additional information was given and, as we have commenced a detailed study of binary mixtures containing CS2, it seemed of interest to produce a complete phase diagram. In addition the excess molar volume VE was measured for this mixture and for the related mixture carbon disulphide + benzene at 298.15 K. The purity of all three substances was in excess of 99.9 moles per cent. The purification techniques and the experimental methods have been given previously.(244’ The phase diagram for {xCS, + (1 -x)C6F6} is given in figure 1. The existence of an
170 -0
A-A-Ad-A-A-A-A-Al I 0.2 0.4
I 0.6
FIGURE 1. The phase diagram for {xC$+(l-x)CaFB}. A, eutectic. a To whom correspondence should be addressed. 0021-9614/78/121205+03 $01.00/O
A-A-A-A-
4 I 0.8
0, Freezing
I curve; n , peritectic;
0 1978 Academic Press Inc. (London)
Ltd.
1206
NOTE
incongruently melting compound of composition 2&F, =CS, was identified by measuring the lengths of the arrest times at the peritectic temperature, 266.1 K. One notable feature of figure 1 is the extremely small slope of the freezing curve over a wide range of composition. This is evidence of large positive deviations from ideality and leads to a eutectic composition xr(CS,) > 0.99 and a eutectic temperature indistinguishable from the freezing temperature of pure CS,. In this respect the phase diagram closely resembles that for carbon disulphide + 1,5-hexadiyne.(” The excess molar volumes for (xCS, + (1 -x&H,) and {xCS, +(I -x)CgF6} at 298.15 K are tabulated in table 1 as a function of X. Also given are the deviations SVE calculated from the smoothing equation : SV,” = V,E(expl)-x(1 -x)(&+ Vi(l-2x)+ V,(1-2~)~). (1) The coefficients V,, V,, and I’, are given in table 2 together with the standard deviations o(Vz) and the smoothed values of Vz(x = 0.5). TABLE
1. Excess
molar
v:
volume Vz for {xC&+(l -x)C,X,} at 298.15 6 Vz calculated from equation (1) and table 2
1oViv:
x
cm3 mol-1
cm3 mol-’
0.2720 0.3224 0.4151 0.4842 0.5022
0.4000 0.4483 0.5041 0.5213 0.5272
-27 +19
+I6
0.2948 0.3807 0.3897 0.4139 0.4336
1.680 1.975 2.007 2.050 2.068
x
-
104&v: .~-v,“cm3 mol - 1 cm3 mol - 1
K and
the deviations
lO%P -.111-m-VE cm3 mol - 1 cm3 mol - 1
x
CsHs
-21 +13
0.5154 0.5536 0.6082 0.6293 0.6506
0.5230 0.5279 0.5149 0.5056 0.4949
-15 +5 +14 +17 -19
0.4401 0.5220 0.5399 0.6084 0.7129
2.123 2.199 2.192 2.178 1.948
-39 120 -t8 -6 -13
0.6587 0.7080 0.7624
0.4930 0.4584 0.4090
$11 -7 -5
+24
0.7157 0.7458 0.7614 0.8325
1.920 1.832 1.748 1.430
-23 -4 -25 +19
C.&i
TABLE
csxs C&s GF,
2. Smoothing
coefficients ___- VO cm3 mol-’ 2.1025 8.7036
and standard --__ VI cm3 moI-l -0.2205 --I .6379
+9 -3 +12 -3
deviations
for {xCSz+(l
Vi? cm3 mol-’ 0.1533 0.7363
-x)CGXB} ~-104(Vo,E) cm3 mol - 1 21 179
at 298.15
K
V,“(x = 0.5) cm3 mol-’ 0.526 2.176
There appear to be no previous measurements on these systems with which to compare the present results. Both VE curves are slightly skewed towards high mole fractions of CS, with maxima at x = 0.528 and x = 0.550 for {xCS, +(I -x)C,H,} and {xCS, + (1 -x)&F,}. By ,coincidence V,” for (xCS, + (1 -x)CsHs} is virtually identical to that for {xCS, + (1 -x)c-C,H,,} at the same temperature.‘2’ There is a similar close similarity between I/ z for {xCS, +(I -x)&F,} and that for
NOTE
1207
{xC,H,,+(~ -x)C,F,}. (5) This latter mixture also exhibits incongruently melting solid compounds and the large positive VE’s are evidence of weak unlike intermolecular interactions and large positive deviations from ideality.‘6, ‘) R.J.H. gratefully acknowledges the award of a N.I. Department of Education Postgraduate Studentship and the authors would like to thank the S.R.C. for the provision of essential equipment. REFERENCES !. Ott, J. B.; Goates, J. R.; Reeder, J.; Shirts, R. B. J. CZxm. Sm. Faraday Trans. Z 1974,70, 1325. 2. Hill, R. J.; O’Kane, E.; Swinton, F. L. J. Chem. Thermodynamics 1978, 10, 1153. 3. Brennan. J. S.: Hill. R. J.: Swinton. F. L. J. Chem. Thermodvnamics 1978. 10. 169. 4. Brennan; J. S.; Brown, N. M. D.; Swinton, F. L. J. Chem. So;. Faraday Tt&s: Z 1974,70, 1965. 5. Duncan, W. A.; Sheridan, J. P.; Swinton, F. L. Trans. Faraday Sot. 1966, 62, 1090. 6. Swinton, F. L. In Molecular Complexes, Vol. 2, R. Foster: editor. Elek Science: London. 1974, p. 63. 7. Swinton, F. L. In Chemical Thermodynamics, Vol. 2, M. L. McGlashan: editor. Chem. SOL: London. 1978.