J. Chem. Thermodynamics 2002, 34, 861–873
doi:10.1006/jcht.2001.0943
Available online at http://www.idealibrary.com on
Partial molar volumes of organic solutes in water.
VII. o- and p-Aminobenzoic acids at T = 298 K
to 498 K and o-diaminobenzene at T = 298 K to
573 K and pressures up to 30 MPa
Pavel Hynčica, Lubomı́r Hnědkovský, and Ivan Cibulka
Department of Physical Chemistry, Institute of Chemical Technology,
166 28 Prague, Czech Republic
Density data for dilute aqueous solutions of two isomeric aminobenzoic acids and
of o-diaminobenzene (1,2-diaminobenzene) are presented together with partial molar
volumes calculated from the experimental data. The measurements were performed at
temperatures from 298.15 K up to either 498.15 K (aminobenzoic acids) or 573.15 K (odiaminobenzene) and at either atmospheric pressure, or at pressures close to the saturated
vapour pressure of water, and also at pressure p = 30 MPa. The data were obtained
using either a high-temperature and high-pressure flow vibrating-tube densimeter for
measurements at elevated pressures or a commercial vibrating-tube cell DMA 602HT for
c 2002 Elsevier Science Ltd. All rights reserved.
measurements at atmospheric pressure. KEYWORDS: density; partial molar volume; aqueous aminobenzoic acids; aqueous
diaminobenzene; high temperature; high pressure
1. Introduction
This study is a continuation of a systematic investigation of partial molar volumes
of benzene derivatives in dilute aqueous solutions. Data on hydroxybenzene (phenol), (1) hydroxy-methylbenzenes (cresols), (2) dihydroxybenzenes, (3) aminobenzene
(aniline), (4) benzoic acid and its hydroxyderivatives, (5) aminomethylbenzenes (toluidines), (6) and chlorophenols (7) have been already published. This paper presents new
data on two aminobenzoic acids, i.e. 1-carboxy-2-aminobenzene (o-aminobenzoic
acid) and 1-carboxy-4-aminobenzene ( p-aminobenzoic acid), and 1,2-diaminobenzene
(o-diaminobenzene, o-phenylendiamine) obtained using a high-temperature and highpressure (HTHP) vibrating-tube densimeter constructed in our laboratory (1, 3, 7) and a
commercial vibrating-tube cell DMA 602HT.
0021–9614/02
c 2002 Elsevier Science Ltd. All rights reserved.
862
P. Hynčica, L. Hnědkovský, and I. Cibulka
2. Experimental
The period of the vibrating tube of the HTHP densimeter was measured by means of
a counter with an uncertainty of about ±0.2 ns, which corresponds to ±10−3 kg · m−3
in density. Repeated calibrations of the densimeter were performed using water and
nitrogen whose densities were taken from the literature. (8, 9) The experimental procedure
is described in more details elsewhere. (1) The maximum systematic error of the measured
density differences {ρ (solution) −ρ (water)} resulting from the densimeter calibration was
about 0.15 per cent and the reproducibility of the measurements was ±5 · 10−3 kg · m−3
in most cases.
The temperature of the HTHP cell was measured using a calibrated (ITS 90) platinum
resistance thermometer (BURNS Engineering), with a resistance R0 = 100  at T =
273.15 K, connected to a multimeter in a four-lead configuration. The resolution of the
temperature measurements was 0.1 mK. The temperature stability of the cell during one
experiment (measurement of one sample) was within ±1 mK. The total uncertainty of the
temperature measurements was estimated to be about ±20 mK at T = 298 K and ±0.10 K
at T = 573 K.
The pressure was measured by means of a strain gauge (DPI 280, Druck Ltd., calibrated
by the manufacturer) with an accuracy of ±0.1 per cent or ±1 · 10−2 MPa, whichever
is greater. The pressure stability was within ±1 · 10−2 MPa at lower pressures and
±3 · 10−2 MPa at p = 30 MPa.
Density measurements at atmospheric pressure and temperatures up to 338.15 K
were performed using the measuring cell of a vibrating-tube densimeter DMA 602HT
(manufactured by Anton Paar, Austria) connected to the same counter that was employed
in connection with the HTHP densimeter. Water and air were used to calibrate the DMA
602HT cell. A water circulating thermostat ensured a temperature stability of ±1 mK.
The uncertainty in the measured temperature (ITS 90) by the quartz thermometer (Testo,
Model 781) is estimated to be about ±20 mK.
The organic solutes o-aminobenzoic acid (stated mass fraction purity > 0.98),
p-aminobenzoic acid (stated mass fraction purity > 0.99), and o-diaminobenzene (stated
mass fraction purity > 0.990), were purchased from Fluka and were used without further
treatment. Distilled, demineralized (Millipore RQ, France) and degassed water was used
as both a solvent and a calibration fluid for the densimeters. Nitrogen (Linde, mole fraction
purity = 0.9999) was used as supplied. The solutions were prepared by weighing using a
Precisa 40SM-200A balance (resolution = 10−2 mg, accuracy = ±0.1 mg) to determine
the mass of the solute and a Precisa 2200C SCS balance (resolution = 10 mg, estimated
accuracy = ±2 · 10−2 per cent) to determine the total mass of a solution. The mass of each
prepared solution was about 1 kg. The estimated uncertainty of the solute molality m 2 was
estimated to be ±2 · 10−5 mol · kg−1 . The solutions were stored in the dark. Some organic
solutes may decompose at high temperatures (3, 5) which would always be accompanied by
a distortion of the course baseline or sample plateau. No such indication of decomposition
of aqueous 1,2-diaminobenzene was observed up to the highest experimental temperature
(573 K) but the decomposition of both aminoacids was evident at temperatures higher
than 498 K.
Vm,2 of aminobenzoic acids(aq) and diaminobenzene(aq)
863
V om,2 /(cm 3 . mol −1)
160
140
120
100
300
350
400
T/K
450
500
◦
o
FIGURE 1. Behaviour of the partial molar volume Vm,2
of o-aminobenzoic acid ( ), and of
p-aminobenzoic acid () at infinite dilution as a function of temperature T for the low-pressure
data. The lines serve only to join the data.
3. Results
DIRECT EXPERIMENTAL DATA
Table 1 presents the measured values of the density differences 1ρ = ρ − ρ1 where ρ and
ρ1 are the densities of the solution and water, respectively, and the molalities of organic
solutes m 2 at various temperatures and pressures. The lowest experimental pressures were
chosen to be either equal to atmospheric pressure at temperatures below the normal boiling
temperature of water, or slightly above the saturated vapour pressure of water at higher
temperatures. No data are presented for aqueous o-aminobenzoic acid at T = 498.15 K
and p = 30 MPa since the measured density differences were lower than the resolution of
the densimeter, i.e. no sample plateau could be recognized within the stability of the tube
oscillations.
The dependence of 1ρ/m 2 on m 2 at constant temperature and pressure was found to be
a linear function of m 2 in the molality ranges of measurements. The experimental results
obtained for individual temperatures and pressures were fitted to the equation
1ρ/m 2 = (ρ − ρ1 )/m 2 = a + bm 2 ,
(1)
where a and b are adjustable coefficients. The values of the coefficients were obtained by
using a weighted least-squares method, and are shown in table 2. A relative statistical
864
P. Hynčica, L. Hnědkovský, and I. Cibulka
TABLE 1. Experimental values of the molality m 2 and density difference
1 ρ = ρ − ρ 1 where ρ is the density of the solution and ρ1 is the density
of water
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
1-carboxy-2-aminobenzene (o-aminobenzoic acid)
T a = 298.15 K
0.01102
0.302
0.02222
0.446
p = 0.1 MPa
0.02200
0.609
0.03294
0.660
0.03294
0.660
0.01201
0.441
0.02200
0.606
0.01201
0.443
0.03300
0.913
0.02196
0.811
0.03300
0.911
0.02196
0.810
T = 373.15 K
0.01109
0.225
0.03196
1.188
p = 30.0 MPa
0.01109
0.228
0.03196
1.187
T = 443.15 K
p = 30.0 MPa
0.01102
0.307
0.02222
0.452
T = 298.15 K
0.01102
0.308
0.02222
0.448
p = 30.0 MPa
0.02200
0.618
0.02222
0.445
0.01102
0.392
0.02200
0.621
0.03294
0.660
0.01102
0.392
0.02200
0.619
0.03294
0.668
0.02200
0.795
0.03300
0.932
0.03294
0.669
0.02200
0.792
0.03300
0.929
0.03300
1.188
0.03300
1.197
T = 408.15 K
p = 2.0 MPa
T = 473.15 K
p = 2.0 MPa
0.01109
0.121
T a = 318.15 K
0.01102
0.265
0.01109
0.123
p = 0.1 MPa
0.01102
0.264
0.02222
0.248
0.01109
0.380
0.02200
0.535
0.02222
0.245
0.01109
0.381
0.02200
0.535
0.03294
0.363
0.02222
0.764
0.03300
0.806
0.03294
0.367
0.02222
0.761
0.03300
0.805
0.03294
1.129
T = 408.15 K
0.03294
1.131
p = 30.0 MPa
T = 473.15 K
p = 30.0 MPa
0.01109
0.120
T a = 338.15 K
0.01102
0.273
0.01109
0.118
p = 0.1 MPa
0.01102
0.273
0.02222
0.247
0.01109
0.350
0.02200
0.549
0.02222
0.253
0.01109
0.350
0.02200
0.551
0.03294
0.375
0.02222
0.700
0.03300
0.827
0.03294
0.379
0.02222
0.704
0.03300
0.829
0.03294
1.038
T = 443.15 K
0.03294
1.041
p = 2.0 MPa
T = 498.15 K
p = 3.0 MPa
0.02222
−0.006
T = 373.15 K
0.01109
0.226
0.02222
−0.016
p = 2.0 MPa
0.01109
0.227
0.03294
−0.019
0.02222
0.448
0.03294
−0.023
0.01102
0.304
Vm,2 of aminobenzoic acids(aq) and diaminobenzene(aq)
865
TABLE 1—continued
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
1-carboxy-4-aminobenzene ( p-aminobenzoic acid)
T a = 298.15 K
0.01199
0.311
p = 0.1 MPa
0.03598
0.885
0.02436
0.636
0.01195
0.401
0.02436
0.637
T = 443.15 K
0.01195
0.403
0.03591
0.942
0.02390
0.817
0.03591
0.944
0.01251
0.286
0.02390
0.811
T = 373.15 K
0.02394
0.508
0.03599
1.207
p = 30.0 MPa
0.02394
0.506
0.03599
1.206
p = 2.0 MPa
0.01251
0.288
0.01199
0.315
0.02493
0.564
T = 298.15 K
0.01199
0.312
0.02493
0.565
p = 30.0 MPa
0.01199
0.319
0.03546
0.795
0.01200
0.400
0.02436
0.648
0.03546
0.794
0.01200
0.400
0.02436
0.649
0.03592
0.770
0.02401
0.808
0.03591
0.957
0.03592
0.772
0.02401
0.803
0.03591
0.957
0.03592
0.773
0.03602
1.212
T = 408.15 K
T = 443.15 K
0.03602
1.209
p = 2.0 MPa
p = 30.0 MPa
T a = 318.15 K
0.01221
0.297
0.01221
0.265
p = 0.1 MPa
0.01221
0.298
0.01221
0.267
0.01264
0.391
0.02432
0.590
0.01221
0.278
0.01264
0.396
0.02432
0.590
0.02432
0.552
0.02448
0.767
0.03426
0.830
0.02432
0.548
0.02448
0.770
0.03426
0.830
0.03426
0.774
0.03589
1.130
T = 408.15 K
0.03426
0.774
0.03589
1.130
p = 30.0 MPa
T a = 338.15 K
0.01203
0.298
p = 0.1 MPa
T = 473.15 K
p = 2.0 MPa
0.01203
0.297
0.01251
0.241
0.01223
0.357
0.01221
0.308
0.01251
0.241
0.01223
0.357
0.01221
0.305
0.02493
0.473
0.02444
0.714
0.02400
0.590
0.02493
0.472
0.02444
0.717
0.02400
0.589
0.03546
0.669
0.03589
1.050
0.02432
0.603
0.03546
0.668
0.03589
1.054
0.02432
0.603
T = 373.15 K
0.03426
0.849
p = 2.0 MPa
0.03426
0.849
0.01251
0.241
0.03598
0.885
0.01251
0.245
0.01199
0.313
T = 473.15 K
p = 30.0 MPa
866
P. Hynčica, L. Hnědkovský, and I. Cibulka
TABLE 1—continued
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
1-carboxy-4-aminobenzene ( p-aminobenzoic acid)
0.02493
0.474
0.03589
0.481
0.02493
0.475
0.03589
0.478
0.03546
0.672
T = 498.15 K
0.03546
0.667
p = 30.0 MPa
T = 498.15 K
0.01223
0.170
p = 3.0 MPa
0.01223
0.171
0.01223
0.177
0.02444
0.327
0.01223
0.174
0.02444
0.323
0.02444
0.337
0.03589
0.464
0.02444
0.335
0.03589
0.463
1,2-diaminobenzene (o-diaminobenzene)
T a = 298.15 K
0.17969
2.337
0.06001
0.623
p = 0.1 MPa
0.17969
2.338
0.06001
0.621
1.240
0.05992
0.867
0.23490
3.043
0.12001
0.05992
0.866
0.23490
3.045
0.12001
1.241
0.11974
1.735
T a = 338.15 K
0.23970
2.448
0.11974
1.735
p = 0.1 MPa
0.23970
2.448
0.18009
2.593
0.06176
0.737
T = 408.15 K
0.18009
2.594
0.06176
0.738
p = 2.0 MPa
0.23976
3.448
0.11619
1.386
0.06001
0.23976
3.447
0.11619
1.388
0.06001
0.553
T = 298.15 K
0.17041
2.022
0.06017
0.566
p = 30.0 MPa
0.554
0.17041
2.023
0.06017
0.564
0.05998
0.869
0.23490
2.773
0.12001
1.102
0.05998
0.808
0.23490
2.776
0.12001
1.102
0.14297
1.916
T = 373.15 K
0.12027
1.112
0.14297
1.914
p = 2.0 MPa
0.12027
1.112
0.25282
3.378
0.17898
1.647
0.25282
3.368
0.06001
0.629
0.06001
0.626
0.17898
1.649
T a = 318.15 K
0.12001
1.251
0.23970
2.181
p = 0.1 MPa
0.12001
1.250
0.23970
2.181
0.05890
0.783
0.23970
2.468
0.23981
2.186
0.05890
0.774
0.23970
2.470
0.23981
2.188
0.12034
1.577
T = 373.15 K
T = 408.15 K
0.12034
1.573
p = 30.0 MPa
p = 30.0 MPa
Vm,2 of aminobenzoic acids(aq) and diaminobenzene(aq)
867
TABLE 1—continued
m2
mol · kg−1
1ρ
kg · m−3
0.06001
0.562
0.11974
0.932
0.23664
1.887
0.06001
0.562
0.18009
1.394
0.23664
1.892
0.12001
1.120
0.18009
1.394
0.12001
1.122
0.23664
1.819
0.23970
2.210
0.23664
1.824
0.23970
2.214
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
1,2-diaminobenzene (o-diaminobenzene)
T = 443.15 K
p = 2.0 MPa
T = 523.15 K
p = 5.0 MPa
0.06176
0.449
T = 473.15 K
0.06176
0.436
p = 30.0 MPa
0.06176
0.438
0.06017
0.516
0.11619
0.832
0.05890
0.482
0.06017
0.517
0.11619
0.829
0.05890
0.480
0.06017
0.505
0.11619
0.831
0.05890
0.463
0.12027
0.998
0.17041
1.209
0.12034
0.982
0.12027
0.999
0.17041
1.210
0.12034
0.977
0.17898
1.479
0.23490
1.651
0.17969
1.468
0.17898
1.479
0.23490
1.660
0.17969
1.468
0.23664
1.960
0.17969
1.467
0.23664
1.967
0.23557
1.919
T = 498.15 K
0.06176
0.492
0.23557
1.918
p = 3.0 MPa
0.06176
0.490
0.23557
1.916
0.06176
0.497
0.05992
0.444
T = 523.15 K
p = 30.0 MPa
T = 443.15 K
0.05992
0.445
0.11619
0.925
p = 30.0 MPa
0.11974
0.888
0.11619
0.931
0.05890
0.512
0.11974
0.887
0.17041
1.359
0.05890
0.509
0.18009
1.327
0.23490
1.864
0.12034
1.039
0.18009
1.327
0.23490
1.861
0.12034
1.036
0.23664
1.733
0.17969
1.549
0.23664
1.734
0.17969
1.544
0.23976
1.765
0.23557
2.027
0.23976
1.763
0.23557
2.022
T = 473.15 K
p = 2.0 MPa
T = 548.15 K
p = 7.0 MPa
0.05992
0.426
0.05992
0.428
T = 498.15 K
0.11974
0.833
p = 30.0 MPa
0.11974
0.832
0.05992
0.488
0.18009
1.251
0.05992
0.471
0.05992
0.484
0.18009
1.248
0.05992
0.472
0.11974
0.967
0.23976
1.656
0.06017
0.474
0.11974
0.966
0.23976
1.653
0.06017
0.474
0.18009
1.447
T = 548.15 K
0.11974
0.930
0.18009
1.444
p = 30.0 MPa
868
P. Hynčica, L. Hnědkovský, and I. Cibulka
TABLE 1—continued
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
m2
mol · kg−1
1ρ
kg · m−3
0.05992
0.487
0.06176
0.440
0.06176
0.527
0.05992
0.484
0.11619
0.815
0.11619
0.969
0.11974
0.959
0.11619
0.805
0.11619
0.976
0.11974
0.961
0.17041
1.184
0.17041
1.401
0.18009
1.436
0.17041
1.188
0.17041
1.413
0.18009
1.441
0.17041
1.174
0.23490
1.915
0.23976
1.919
0.23490
1.622
0.23490
1.926
0.23976
1.907
0.23490
1.645
0.23976
1.907
0.23490
1.631
T = 573.15 K
T = 573.15 K
p = 10.0 MPa
p = 30.0 MPa
0.06176
0.434
0.06176
0.523
a DMA 602HT cell.
140
V om,2 /(cm 3 . mol − 1)
130
120
110
100
90
300
350
400
450
500
550
T/K
o of o-diaminobenzene at infinite dilution as
FIGURE 2. Behaviour of the partial molar volume Vm,2
a function of temperature T : , low-pressure data; , data at 30 MPa. The lines serve only to join
the data.
◦
•
Vm,2 of aminobenzoic acids(aq) and diaminobenzene(aq)
869
25
∆V om,2 /(cm 3 . mol −1)
20
15
10
5
0
−5
300
350
400
T/K
450
500
o
o
FIGURE 3. Deviation of the partial molar volume at infinite dilution 1Vm,2
= Vm,2
o
(o-aminobenzoic acid)—Vm,2 ( p-aminobenzoic acid) as a function of temperature T : , lowpressure data; , data at 30 MPa. The line serves only to join the data.
•
◦
weight for each value 1ρ/m 2 was calculated from the estimated uncertainties of 1ρ
and m 2 .
PARTIAL MOLAR VOLUMES
o is obtained from
The partial molar volume at infinite dilution (m 2 → 0) of a solute Vm,2
equation (1) as (1)
o
Vm,2
= (1/ρ1 ){M2 − (a/ρ1 )},
(2)
where M2 is the molar mass of the solute.
The partial molar volumes at infinite dilution calculated from the experimental data
o given
and their estimated uncertainties are presented in table 2. The uncertainties in Vm,2
in table 2 include random error estimates that originate from the scatter associated with
equation (1) as well as errors in the temperature, pressure, and calibration constant. No
partial molar volumes for the investigated aqueous solutes were found in the literature.
Figures 1 and 2 present the temperature dependence of the partial molar volume
at infinite dilution for the solutes investigated. The plots for both aminobenzoic acids
(figure 1) are shown for the low-pressure data only, and a similar picture can be obtained
for the isobar p = 30 MPa. Unlike for o-diaminobenzene (figure 2) partial molar
870
P. Hynčica, L. Hnědkovský, and I. Cibulka
0.5
− (∂Vom,2 / ∂p)T /(cm 3 . mol −1 . MPa−1)
0.4
0.3
0.2
0.1
0
300
350
400
450
500
550
T/K
◦
o /∂ p) as a function of temperature T : , o-aminobenzoic acid; 4,
FIGURE 4. Derivative −(∂ Vm,2
T
p-aminobenzoic acid; , o-diaminobenzene. The error bars represent ±2σ where σ is estimated
o ) (table 2) and the pressure measurement uncertainty.
from the standard deviation σ (Vm,2
•
o /dT ) at about
volumes of aminobenzoic acids (figure 1) exhibit a steep increase in (dVm,2
the temperature 450 K. As mentioned in the Experimental Section the decomposition
of the acids was observed at temperatures higher than 500 K. No difficulties were
encountered at lower temperatures and thus it would be rather speculative to attribute this
behaviour to solute decomposition. The solutions were measured simultaneously and thus
a systematic error caused by the experimental technique (including the calibration of the
densimeter) could not explain the differences between the data obtained. The values of the
o /dT ) for both aminobenzoic acids are close to each other at the lower
derivative (dVm,2
temperatures, but at higher temperatures the derivative for o-aminobenzoic acid becomes
o (T ) deviate. Figure 3 shows the
significantly larger and the temperature behaviours of Vm,2
o
o
o
temperature dependence of the difference 1Vm,2 = Vm,2 (o-aminobenzoic acid) − Vm,2
( p-aminobenzoic acid) for both pressure sets. The difference follows a smooth curve nearly
identical for both pressure sets (only one curve, common for both pressure sets, is therefore
drawn in the figure). The magnitude of the difference at higher temperatures is, however,
rather large compared with that of the ortho- and para-isomers of the disubstituted benzene
derivatives studied so far (cresols, (2) dihydroxybenzenes, (3) hydroxybenzoic acids, (5)
toluidines, (6) chlorophenols (7) ). Specific solute–solvent interactions and intramolecular
interactions between the amino and carboxylic groups bonded to the benzene ring at
Vm,2 of aminobenzoic acids(aq) and diaminobenzene(aq)
871
TABLE 2. Coefficients a and b of equation (1) and extrapolated values of the partial
o for {aminobenzoic acid(2) + water (1)} or {1,2molar volumes at infinite dilution Vm,2
diaminobenzene(2) + water(1)}. The standard deviations σ (a) and σ (b) refer to the
o ) represents the total estimated uncertainty.
coefficients a and b of equation (1), σ (Vm,2
ρ1a
a
σ (a)
kg2 · m−3 · mol−1
b
σ (b)
kg3 · m−3 · mol−2
o
Vm,2
o )
σ (Vm,2
3
−1
cm · mol
T
K
p
MPa
kg · m−3
298.15b
0.1
997.041
36.50
0.09
20.18
3.2
100.83
0.12
318.15b
0.1
990.202
34.32
0.10
−0.56
3.3
103.49
0.13
338.15b
0.1
980.549
31.61
0.13
−1.4
4.5
106.99
0.17
373.15
2.0
959.256
27.49
0.12
4.6
3.9
113.09
0.15
408.15
2.0
931.462
23.95
0.10
14.3
3.3
119.63
0.15
443.15
2.0
898.269
20.47
0.11
−13.6
3.7
127.30
0.17
473.15
2.0
865.094
11.03
0.15
1.7
5.1
143.79
0.24
1-carboxy-2-aminobenzene (o-aminobenzoic acid)
498.15
3.0
298.15
30.0
373.15
30.0
408.15
30.0
834.295
0.40
0.38
−31.6
12.1
163.80
0.57
35.37
0.16
27.4
5.7
101.10
0.19
971.843
27.91
0.12
8.9
4.2
111.56
0.16
945.540
24.70
0.12
11.9
3.1
117.41
0.14
1010.12
443.15
30.0
914.738
20.32
0.16
−1.4
5.6
125.64
0.23
473.15
30.0
884.663
10.43
0.16
31.0
5.4
141.69
0.25
498.15c
30.0
856.709
(0.00)
(0.00)
(0.00)
(0.00)
160.08
(0.30)
298.15b
0.1
997.041
33.73
0.25
−3.5
7.4
103.61
0.50
318.15b
0.1
990.202
31.15
0.13
9.6
4.0
106.74
0.18
1-carboxy-4-aminobenzene ( p-aminobenzoic acid)
338.15b
0.1
980.549
29.16
0.12
4.4
3.8
109.53
0.16
373.15
2.0
959.256
25.88
0.08
10.5
2.3
114.84
0.13
408.15
2.0
931.462
24.40
0.05
−5.3
1.2
119.10
0.10
443.15
2.0
898.269
22.42
0.60
−11.0
10.0
124.89
0.76
473.15
2.0
865.094
19.37
0.08
−15.0
2.7
132.64
0.15
498.15
3.0
298.15
30.0
373.15
30.0
408.15
30.0
443.15
834.295
14.72
0.13
−38.2
4.2
143.23
0.24
33.23
0.13
10.5
3.7
103.20
0.18
971.843
26.41
0.12
7.1
4.0
113.16
0.18
945.540
24.97
0.12
−9.5
3.8
117.11
0.18
30.0
914.738
22.69
0.18
−3.0
4.8
122.80
0.26
473.15
30.0
884.663
19.57
0.15
−20.7
4.9
130.01
0.24
498.15
30.0
856.709
14.39
0.11
−41.2
3.2
140.47
0.20
298.15b
0.1
997.041
14.50
0.02
−0.5
0.1
93.87
0.04
318.15b
0.1
990.202
13.21
0.02
−1.1
0.1
95.73
0.04
338.15b
0.1
980.549
12.02
0.02
−0.9
0.1
97.78
0.04
1010.12
1,2-diaminobenzene (o-diaminobenzene)
872
P. Hynčica, L. Hnědkovský, and I. Cibulka
TABLE 2—continued
ρ1a
σ (a)
kg2 · m−3 · mol−1
σ (b)
kg3 · m−3 · mol−2
o
Vm,2
o )
σ (Vm,2
T
K
p
MPa
kg · m−3
373.15
2.0
959.256
10.53
0.02
−0.9
0.1
101.30
0.05
408.15
2.0
931.462
9.34
0.04
−0.9
0.1
105.33
0.07
443.15
2.0
898.269
8.32
0.03
−0.8
0.2
110.08
0.10
473.15
2.0
865.094
7.85
0.02
−0.6
0.2
114.51
0.07
498.15
3.0
834.295
7.45
0.02
−0.4
0.2
118.91
0.05
523.15
5.0
800.236
7.22
0.02
−0.7
0.1
123.86
0.05
548.15
7.0
760.778
7.03
0.02
−0.5
0.1
130.01
0.06
573.15
10.0
715.394
7.06
0.03
−0.5
0.1
137.36
0.08
298.15
30.0
13.49
0.03
−0.7
0.1
93.83
0.05
373.15
30.0
971.843
10.44
0.01
−1.0
0.1
100.22
0.04
408.15
30.0
945.540
9.44
0.02
−0.9
0.1
103.81
0.05
443.15
30.0
914.738
8.66
0.02
−0.3
0.1
107.87
0.06
473.15
30.0
884.663
8.32
0.03
−0.2
0.1
111.61
0.07
498.15
30.0
856.709
8.16
0.02
−0.7
0.1
115.11
0.06
523.15
30.0
825.654
8.06
0.02
−0.6
0.1
119.15
0.08
548.15
30.0
790.751
8.10
0.03
−0.6
0.1
123.81
0.07
573.15
30.0
750.762
8.49
0.04
−1.3
0.2
128.98
0.10
1010.12
a
b
cm3 · mol−1
a Reference 8; b DMA 602HT cell; c Experimental density differences were lower than the
resolution of the densimeter.
neighbouring (ortho-) or distant (para-) positions or ionic behaviour (charge transfer)
might be the cause.
o /∂ p) approximated by using the expression −(1V o /1p) =
Derivatives −(∂ Vm,2
T
m,2
o
o (T, p
−{Vm,2 (T, pmax ) − Vm,2
min )}/( pmax − pmin ), where pmax and pmin are the highest
and the lowest pressure of the measurements at a given temperature, are shown in figure 4.
The changes in the partial molar volume per unit pressure change of o-diaminobenzene
increase monotonously with increasing temperature while a minimum is observed for both
aminobenzoic acids at a temperature close to that at which the temperature dependence
o (T ) (see figure 1) exhibits a sharp increase in (dV o /dT ). The uncertainties in
of Vm,2
m,2
o /∂ p) estimated from the standard deviations σ (V o ) in table 2 using an error−(∂ Vm,2
T
m,2
propagation formula are, however, significantly higher for both aminobenzoic acids than
for o-diaminobenzene (see the error bars shown in figure 4).
Support from the Ministry of Education of the Czech Republic (fund MSM 223400008) is
acknowledged.
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873
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