Standard molar enthalpies of formation of three N-benzoylthiocarbamic-O- alkylesters

Article abstract of DOI:10.1016/j.jct.2004.03.004

The standard molar enthalpies of combustion in oxygen of three crystalline N-benzoylthiocarbamic-O-alkylesters were measured at T=298.15 K by rotating bomb calorimetry. The standard molar enthalpy of sublimation of the three compounds were measured using

Full text of DOI:10.1016/j.jct.2004.03.004

J. Chem. Thermodynamics 36 (2004) 491–495
www.elsevier.com/locate/jct
Standard molar enthalpies of formation of three
N-benzoylthiocarbamic-O-alkylesters
a,
a
a
*
Manuel A.V. Ribeiro da Silva , Luis M.N.B.F. Santos , Bernd Schr o€ der ,
b
Frank Dietze , Lothar Beyer
b
a
Centro de Investigacß ~a o em Qu ꢀı mica, Departamento de Qu ꢀı mica, Faculdade de Ci ^e ncias, Universidade do Porto, Rua do Campo Alegre, 687,
P-4169-007 Porto, Portugal
b
Institut f €u r Anorganische Chemie, Universit €a t Leipzig, Johannisallee 29, D-04103 Leipzig, Germany
Received 19 January 2004; accepted 1 March 2004
Available online 15 April 2004
Abstract
ꢀ
The standard (p ¼ 0:1 MPa) molar enthalpies of combustion in oxygen of three crystalline N-benzoylthiocarbamic-O-alky-
lesters, PhCONHCSOR, R ¼ Et (Hbtcee), n-Bu (Hbtcbe), n-Hex (Hbtche), were measured at T ¼ 298:15 K by rotating bomb
calorimetry. The standard molar enthalpies of sublimation of the three compounds were measured using Calvet microcalorimetry.
These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous
phases, respectively.
ꢀ
ꢁ1
g
cr
ꢀ
m
ꢁ1
)
ꢁ
D
c
U (cr)/(kJ ꢂ mol
)
D H /(kJ ꢂ mol
m
N-benzoylthiocarbamic-O-ethylester
N-benzoylthiocarbamic-O-n-butylester
N-benzoylthiocarbamic-O-n-hexylester
5777.9 ꢃ 2.2
7094.5 ꢃ 2.5
8402.2 ꢃ 3.1
112.2 ꢃ 1.3
120.7 ꢃ 1.8
139.7 ꢃ 2.4
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Enthalpy of combustion; Enthalpy of sublimation; N-benzoylthiocarbamic-O-ethylester; N-benzoylthiocarbamic-O-n-butylester;
N-benzoylthiocarbamic-O-n-hexylester
1
. Introduction
towards metal ions was the subject of investigations
9]. They were proposed as intermediates in regio-
[
N-benzoylthiocarbamic-O-alkylesters had their first
and chemoselective deoxygenation of primary and
secondary aliphatic alcohols [10]. The first reference
due to their coordinating properties was published in
1995 [11]; recently, more attention has been devoted
to their thermodynamical behaviour in solution
[12].
There are no reported values for thermochemical
properties of the N-benzoylthiocarbamic-O-alkylesters
so far, neither in the condensed nor in the gaseous
phases. As part of a broad thermochemical study on
compounds containing double bonded oxygen as well as
sulphur (e.g. monothio-b-diketones and N-acylthiou-
reas) this paper reports on the thermochemistry of the
appearance as early as 1874 reported by L o€ ssner [1]
followed by the identification by Dixon [2] in 1895.
Although mainly used in heterocyclic chemistry in the
late 60s of the last century [3–6] and applied as col-
lectors in ore flotation processing [7,8], they seem to
have been overlooked as chelating ligands in spite of
their easy synthetical access. Also, the extraction be-
haviour of the N-benzoylthiocarbamic-O-alkylesters
*
Corresponding author. Tel.: +351-22-6082-821; fax: +351-22-6082-
8
22.
E-mail address: risilva@fc.up.pt (M.A.V. Ribeiro da Silva).
0
021-9614/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jct.2004.03.004

492
M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 36 (2004) 491–495
3
. Combustion calorimetry
O
S
The enthalpies of combustion were measured with the
rotating-bomb calorimeter formerly used at the Na-
tional Physical Laboratory, Teddington, UK [13], with a
R
N
O
H
3
platinum-lined bomb of internal volume 0.337 dm .
Water was added to the calorimeter from a weighed
acrylic vessel, and for each experiment a correction to
the energy equivalent was made for the deviation from
4059.0 g of the mass of water added. Calorimetric
temperatures were measured to 1 ꢂ 10ꢁ K with a quartz
thermometer (Hewlett Packard HP 2804) interfaced to a
microcomputer programmed to compute the adiabatic
temperature change. Ignition temperatures were chosen
so that the final temperatures were very close to 298.15
K. Fore-period readings were taken for about 20 min,
the main period was about 25 min and the after period
about 20 min. The frictional work of bomb rotation was
automatically included in the correction for heat ex-
change and work of stirring by using the procedure
described by Good et al. [14].
FIGURE 1. General formula of the N-benzoylthiocarbamic-O-alky-
lester.R ¼ Et:N-benzoylthiocarbamic-O-ethylester(Hbtcee);R ¼ n-Bu:
N-benzoylthiocarbamic-O-n-butylester (Hbtcbe); R ¼ n-Hex: N-ben-
zoylthiocarbamic-O-n-hexylester (Hbtche).
4
following compounds: N-benzoylthiocarbamic-O-ethy-
lester (Hbtcee), N-benzoylthiocarbamic-O-n-butylester
(
(
Hbtcbe), and N-benzoylthiocarbamic-O-n-hexylester
Hbtche), as shown in figure 1.
The presented results enabled the standard molar
enthalpies of formation in both crystalline and gaseous
phases to be derived.
The energy equivalent of the calorimeter was deter-
mined from the combustion of benzoic acid (Bureau of
Analysed Samples; Thermochemical Standard BCS-
CRM 190-r), as described previously [15]. The electrical
energy for the ignition was determined from the change
in potential across a capacitor when 40 V were dis-
charged through a platinum ignition wire. For the cot-
ton thread fuse (empirical formula CH1:686O0:843), the
massic energy of combustion is assigned to
The obtained data for the condensed and gaseous
phases are necessary for a thermochemical study of the
metal complexes, in order to derive thermochemical
parameters for the metal–ligand binding.
2
. Experimental
The N-benzoylthiocarbamic-O-alkylesters
ꢀ
ꢁ1
were
ꢁD u ¼ 16250 J ꢂ g
[15], a value which has been
confirmed in our laboratory. Corrections for nitric acid
c
prepared as described earlier [11]: 0.1 mol (16.3 g)
of benzoyl isothiocyanate were dissolved in 60 cm3
of toluene; the corresponding alcohol was added
dropwise in twofold molar excess at room tempera-
ture under stirring and slowly heated up to 333 K
for 1 h. Overnight, the reaction mixture was evap-
orated to dryness. The remaining crude solid was
dissolved in methanol, and water was added up to
maintaining turbidness. Continually repeating of this
procedure leads to pure, yellow crystals, with
Tfus ¼ 347 K (Hbtcee), 330–331 K (Hbtcbe) and 346
K (Hbtche).
ꢁ1
formation were based on )59.7 kJ ꢂ mol for the molar
ꢁ
3
energy of formation of 0.1 mol ꢂ dm HNO (aq) from
3
O , N , and H O(l) [16].
2
2
2
From series of eight calibration experiments the en-
ergy equivalent of the calorimeter, e(calor), were found
ꢁ
1
to be (20684.5 ꢃ 4.0) J ꢂ K
(for combustion experi-
ꢁ
1
ments with Hbtcee) and (20690.2 ꢃ 3.3) J ꢂ K
(for
combustion experiments with Hbtcbe and Hbtche series)
for an average mass of water added to the calorimeter of
4059.0 g; the quoted uncertainty refers to the standard
deviation of the mean.
The purity of the samples was checked by i.r. spec-
troscopy and by elemental analysis; the mass fraction w of
C, H, N and S were as follows: for Hbtcee, C10H11NO2S,
Samples in pellet form were ignited in oxygen at a
3
pressure of 3.04 MPa with a volume of 10 cm of water
added to the bomb. The amount of nitric acid was de-
termined using the Devarda alloy method [17]. The
densities of the three crystalline N-benzoylthiocarbamic-
2
2
2
found 10 wðCÞ ¼ 56:94, 10 wðHÞ ¼ 5:22, 10 wðNÞ ¼
2
2
2
6
:86, 10 wðSÞ ¼ 16:37, calculated 10 wðCÞ ¼ 57:39, 10
2 2
ꢁ3
wðHÞ ¼ 5:30, 10 wðNÞ ¼ 6:69, 10 wðSÞ ¼ 15:32; for
O-alkylesters were assumed to be 1.3 g ꢂ cm and for
2
2
ꢁ3
Hbtcbe, C12H15NO2S, found 10 wðCÞ ¼ 60:56, 10
benzoic acid q ¼ 1:32 g ꢂ cm . For each compound,
2
2
wðHÞ ¼ 6:41, 10 wðNÞ ¼ 5:89, 10 wðSÞ ¼ 13:54, calcu-
ðou=opÞ at T ¼ 298:15 K was assumed to be )0.2
T
2
2
2
ꢁ1
ꢁ1
lated 10 wðCÞ ¼ 60:73, 10 wðHÞ ¼ 6:37, 10 wðNÞ ¼
J ꢂ g ꢂ MPa , a typical value for solid organic
2
5
1
:90, 10 wðSÞ ¼ 13:51; for Hbtche, C H NO S, found
compounds [18].
14
19
2
2
2
2
2
0 wðCÞ ¼ 62:73, 10 wðHÞ ¼ 7:19, 10 wðNÞ ¼ 5:24, 10
Standard state corrections were calculated by the
procedures given by Hubbard et al. [19] and by Good
and Scott [20]. The relative atomic masses used were
2
2
wðSÞ ¼ 12:76, calculated 10 wðCÞ ¼ 63:40, 10
2
2
wðHÞ ¼ 7:17, 10 wðNÞ ¼ 5:28, 10 wðSÞ ¼ 12:08.

M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 36 (2004) 491–495
493
those recommended by the IUPAC Commission in 2001
21].
experiments at T ¼ 375 K as K ¼ ð0:9861 ꢃ 0:0050Þ.
The temperature was measured in situ using a small
size Pt100 probe previously calibrated against a SPRT
[
(25 X)Tinsley 5187SA standard probe using an ASL
bridge F26. The dependency of the blank tube sign
from the mass difference of the blank tubes in the
reference and measuring cell was taken into account
4
. Microcalorimetry
The standard molar enthalpies of sublimation were
[
23].
measured using the ‘‘vacuum sublimation’’ drop mi-
crocalorimetric method [22,23]. Samples of about 5 mg
of each compound, contained in thin glass capillary
tubes and sealed at one end, were dropped from room
temperature into the hot reaction vessel in the Calvet
High Temperature Microcalorimeter (SETARAM HT
5. Results
Table 1 lists typical combustion results for each
compound in which Dm (H2O) is the deviation of the
mass added to the calorimeter from 4059.0 g, the mass
assigned to e(calor), and DUR is the correction to the
standard state. The remaining quantities are as previ-
ously described [19].
The internal energy for the isothermal bomb process,
DU(IBP), was calculated according to:
1
000D), held at the temperature T ¼ 375 K and then
removed from the hot zone by vacuum sublimation. The
observed standard molar enthalpies of sublimation
ꢀ
ꢀ
{
2
H ðg; TÞ ꢁ H (cr, 298.15 K)} were corrected to T ¼
m
m
ꢀ
ꢀ
m
98:15 K using {H ðg; TÞ ꢁ H (g, 298.15 K)} esti-
m
mated by a group method based on the values of Stull
et al. [24]. This is, PhCONHCSOEt ¼ PhCHO +
T
ꢀ
HNCS + EtOH ) H2, which gives
D
for Hbtcee, PhCONHCSO-n-
H ðgÞ ¼
DUðIBPÞ ¼ ꢁ feðcalorÞ þ c
ðT ꢁ 298:15Þe þ ð298:15 ꢁ T
DUðignÞ;
p
ðH
2
O; lÞDmðH
2
OÞgDTad þ
2
98:15 K
m
ꢁ
1
ð17:0 ꢃ 1:0Þ kJ ꢂ mol
i
i
i
ꢁ DTadÞe þ
f
T
298:15K
ꢀ
Bu¼PhCHO+HNCS+n-BuOH–H , with D
H ðgÞ
m
2
ð1Þ
ꢁ
1
¼
ð20:8 ꢃ 1:0Þ kJ ꢂ mol
for Hbtcbe, PhCONH
CSO-n-Hex ¼ PhCHO + HNCS + n-HexOH–H2, which
where DTad is the calorimeter adiabatic temperature
change corrected for the heat exchange and the work of
stirring.
T
ꢀ
ꢁ1
gives D
H ðgÞ ¼ ð24:7 ꢃ 1:0Þ kJ ꢂ mol for Hbt-
2
98:15 K
m
che, all at T ¼ 375 K.
The calorimeter was calibrated in situ, making use
of the reported standard molar enthalpy of sublima-
For each compound, the products of combustion in
the experiments consist of a gaseous phase and an
aqueous mixture of sulphuric acid for which the ther-
modynamic properties are known.
g
cr
ꢀ
tion of naphthalene, C H , D H ¼ ð72:513 ꢃ 0:071Þ
10
8
m
ꢁ
1
kJ ꢂ mol [25]. The calibration constant of the calo-
ꢀ
rimeter was obtained as the average of six independent
The values of ꢁDu refer to the reaction
c
TABLE 1
Typical combustion experimental results for N-benzoylthiocarbamic-O-ethylester (Hbtcee), N-benzoylthiocarbamic-O-n-butylester (Hbtcbe), N-
benzoylthiocarbamic-O-n-hexylester (Hbtche), at T ¼ 298:15 K
Hbtcee
Hbtcbe
Hbtche
m(cpd)/g
m (fuse)/g
0.89814
0.79091
0.86827
0
0.00554
297.1467
298.3667
53.93
0.00527
297.1150
298.2926
53.95
0.00561
296.9896
298.3525
4.03
T
T
i
/K
/K
f
1
e
e
i
/(J ꢂ Kꢁ
)
ꢁ
1
f
/(J ꢂ K
)
O)/g
53.46
)18.4
1.20759
24949.25
39.57
53.65
16.9
1.15147
53.96
1.3
1.33318
Dm(H
2
DTad/K
ꢁ
DU(IBP)/J
DU(HNO
DU(ign)/J
23803.60
27661.94
3
)/J
45.48
1.19
26.11
49.11
1.06
28.29
1.20
DU
m D
R
/J
26.58
89.97
0
ꢀ
c
u (fuse)/J
85.58
29897.75
91.11
31664.61
ꢀ
ꢁ1
)
ꢁD
c
u (cpd)/(J ꢂ g
27604.97
DU(IBP) includes DU(ign); m(cpd.) is the mass of compound burnt in each experiment; m (fuse) is the mass of fuse (cotton) used in each
experiment; Ti is the initial temperature; Tf is the final temperature rise; ei is the energy equivalent of contents in the initial state; ef is the energy
equivalent of contents in the final state; Dm(H2O) is the deviation of mass of water added to the calorimeter from 4059.0 g; DTad is the corrected
temperature rise; DU(IBP) is the energy change for the isothermal combustion reaction under actual bomb conditions; DU(HNO3) is the energy
ꢀ
correction for the nitric acid formation; DU(ign) is the electrical energy for ignition; DUR is the standard state correction; Dcu (fuse) is the massic
ꢀ
energy of combustion of the fuse (cotton); Dcu is the standard massic energy of combustion.

494
M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 36 (2004) 491–495
TABLE 4
Observed standard molar enthalpies of sublimation D
N-benzoylthiocarbamic-O-ethylester (Hbtcee), N-benzoylthiocarba-
mic-O-n-butylester (Hbtcbe), N-benzoylthiocarbamic-O-n-hexylester
C
a
H
b
O
c
N
d
S
e
þ ða þ b=4 ꢁ c=2 þ 3e=2ÞO
2
ðgÞ þ
g;T
cr;298:15 K
ꢀ
of
H
m
ð116e ꢁ b=2ÞH OðlÞ ! aCO ðgÞ þ d=2N ðgÞ þ
e½H
2
2
2
Å
2
SO 115H
4
2
OÞꢄðlÞ:
ð2Þ
(
Hbtche), at T ¼ 375 K
Hbtcee
Hbtcbe
Hbtche
Table 2 lists the individual values of ꢁD u together
c
g;T
cr;298:15 K
ꢀ
ꢁ1
)
with the mean and its standard deviation. Table 3 lists
for each compound the derived standard molar values
for the energies and enthalpies of the combustion reac-
tions, DcU and DcH , the standard molar enthalpy of
formation, Df H , of the crystalline solids as well as the
standard molar enthalpies of sublimation and the de-
rived standard molar enthalpies of formation in the
gaseous state. In accordance with the normal thermo-
chemical practice [26], the uncertainties assigned to the
standard molar enthalpies of combustion and formation
are twice the overall standard deviation of the mean and
include the uncertainties in calibration and in the aux-
D
H /(kJ ꢂ mol
m
128.7
141.8
139.8
140.4
143.9
141.5
164.5
163.9
168.3
166.4
162.0
161.4
1
1
1
28.6
29.0
30.3
ꢀ
ꢀ
m
m
ꢀ
m
129.4
g;T
cr;298:15 K
ꢀ
ꢁ1
)
a
hD
H i/(kJ ꢂ mol
m
1
29.2 ꢃ 0.6
141.5 ꢃ 1.4
164.4 ꢃ 2.1
g;T
cr;298:15 K
Mean value; uncertainty given as twice the standard deviation of
ꢀ
The mean values are represented by hD
H i.
m
a
the mean.
ꢀ
iliary quantities used. To derive Df H (cr) from
m
ꢀ
D H (cr), the standard molar enthalpies of formation of
N-benzoylthiocarbamic-O-n-hexylester are given in
Table 4 with uncertainties equal to twice the standard
deviation of the mean.
c
m
H O(l), of CO (g) and H SO in 115 H O(l), at T ¼
2
2
2
4
2
ꢁ
1
2
98:15 K, respectively, )(285.830 ꢃ 0.040) kJ ꢂ mol
1
ꢁ
[
0
27], )(393.51 ꢃ 0.13) kJ ꢂ mol
[27], and )(887.81 ꢃ
ꢁ
1
.01) kJ ꢂ mol were used [16].
The individual results of the measurements of the
enthalpies of sublimation for N-benzoylthiocarbamic-O-
ethylester, N-benzoylthiocarbamic-O-n-butylester and
6
. Discussion
There are no previously determined values for the
standard molar enthalpies of formation of these com-
pounds and, at present, only a limited number of ther-
mochemical studies on compounds containing similar
structures are available.
TABLE 2
Individual values of the massic energy of combustion, ꢁDcu of N-
ꢀ
benzoylthiocarbamic-O-ethy-ester (Hbtcee), N-benzoylthiocarbamic-
O-n-butylester
(Hbtcbe),
N-benzoylthio-carbamic-O-n-hexylester
The obtained results are shown in figure 2 and they
are consistent in themselves. Linear regression gives
ꢀ
(Hbtche), at T ¼ 298:15 K (p ¼ 0:1 MPa)
ꢀ
ꢁ1
2
Hbtcee
Hbtcbe
Hbtche
D H (g)/kJ ꢂ mol ¼ )14.8 ꢂ n ) 183.3
ðr ¼ 0:9991Þ
f
m
C
uꢀ/(J ꢂ gꢁ1
with n as the number of carbon atoms in the alkyl
ꢁD
c
)
C
chain ðnC > 1Þ. The slope of )14.8 kJ ꢂ mol 1, is the
increment in the standard molar enthalpy of formation,
in the gaseous state, due to the CH2-group introduction
in the alkyl chain, which is lower than that normally
observed in linear alkyl chaines, of )20.5 kJ ꢂ molꢁ1,
expected from the Group Scheme. Figure 2 also shows
ꢁ
2
2
2
2
2
2
7605.0
7615.4
7616.1
7611.6
7602.1
7613.0
29897.8
29895.2
29894.2
29896.3
29892.5
29896.3
31664.6
31688.1
31655.6
31663.2
31667.4
31666.8
31665.8
2
9889.9
uꢀi/(J ꢂ gꢁ1
a
the application of this group contribution, [C–(C)(H) ]
2
ꢁ
hD
c
)
)20.5 kJ ꢂ molꢁ [28], on the obtained experimental
1
¼
2
7610.5 ꢃ 4.7
29894.6 ꢃ 2.0
31667.4 ꢃ 7.5
ꢀ
value of N-benzoylthiocarbamic-O-n-butylester; this
procedure leads to values distinctively lying out of the
range of the assigned experimental errors.
The mean values are represented by hDcu i.
a
Mean value; uncertainty given as twice the standard deviation of
the mean.
TABLE 3
ꢀ
ꢀ
ꢀ
Derived standard (p ¼ 0:1 MPa) molar energies of combustion, ꢁDcU , standard molar enthalpies of combustion, DcH , standard molar enthalpies
m
m
ꢀ
g
cr
ꢀ
m
of formation, Df H , and standard molar enthalpies of sublimation, D H , for N-benzoylthiocarbamic-O-ethylester (Hbtcee), N-benzoylthiocar-
m
bamic-O-n-butylester (Hbtcbe), N-benzoylthiocarbamic-O-n-hexylester (Hbtche), at T ¼ 298:15 K
ꢀ
ꢁ1
ꢀ
ꢁ1
ꢀ
ꢁ1
g
cr
ꢀ
ꢁ1
ꢀ
ꢁ1
)
ꢁD
c
U (cr)/(kJ ꢂ mol
)
ꢁD
c
H (cr)/(kJ ꢂ mol
)
ꢁD
f
H (cr)/(kJ ꢂ mol
)
D H /(kJ ꢂ mol
)
ꢁD
f
H (g)/(kJ ꢂ mol
m
m
m
m
m
Hbtcee
Hbtcbe
Hbtche
5777.9 ꢃ 2.2
7094.5 ꢃ 2.5
8402.2 ꢃ 3.1
5784.7 ꢃ 2.2
7103.8 ꢃ 2.5
8414.0 ꢃ 3.1
324.5 ꢃ 2.9
364.1 ꢃ 3.0
411.2 ꢃ 4.0
112.2 ꢃ 1.3
120.7 ꢃ 1.8
139.7 ꢃ 2.4
212.3 ꢃ 3.2
243.4 ꢃ 3.5
271.5 ꢃ 4.7

M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 36 (2004) 491–495
495
320
300
280
260
240
220
200
180
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[
[
[
[
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Hbtcbe
1
9] M. Oba, K. Nishiyama, Synthesis (1994) 624–628.
0–14.
Hbtcee
[
[
10] L. Quas, U. Schr o€ der, B. Schr o€ der, F. Dietze, L. Beyer, Solv. Extr.
Ion. Exch. 18 (2000) 1167–1177.
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Hoyer, J. Prakt. Chem. 337 (1995) 184–188.
1
2
3
4
5
6
7
n
C
[12] B. Schr o€ der, U. Schr o€ der, F. Dietze, L. Beyer, Inorg. Chem.
Commun. 4 (2001) 398–401.
ꢀ
FIGURE 2. Plot of experimental values of Df H (g)ðꢂÞ with the re-
m
[13] J.D. Cox, H.A. Gundry, A.J. Head, Trans. Faraday Soc. 60 (1964)
spective values derived by the Group scheme ðꢀÞ [starting point: N-
benzoylthiocarbamic-O-n-butylester (Hbtcbe)], against the number of
carbons in the alkyl chain nC > 1.
6
53–665.
14] W.D. Good, D.W. Scott, G. Waddington, J. Phys. Chem. 60
1956) 1080–1089.
[
[
(
15] J. Coops, R.S. Jessup, K. Van Nes, in: F.D. Rossini (Ed.),
Experimental Thermochemistry, vol. 1, Interscience, New York,
1956 (Chapter 3).
This difference is possibly an expression for the in-
creasing instability of the molecule caused by a prolon-
gation in the alkyl chain, which may give rise to steric
hindrance in the surroundings of the ester–oxygen- atom.
[16] The NBS Tables of Chemical Thermodynamic Properties, J. Phys.
Chem. Ref. Data 11 (Suppl. 2) (1982).
[
17] A.I. Vogel, Quantitative Inorganic Analysis, Longman, London,
978.
18] E.N. Washburn, J. Res. Natl. Bur. Stand. (US) 10 (1933)
25–528.
[19] W.N. Hubbard, D.W. Scott, G. Waddington, in: F.D. Rossini
Ed.), Experimental Thermochemistry, vol. 1, Interscience, New
1
[
5
Acknowledgements
(
York, 1956, Chapter 5.
This work is part of a joint research project between
the Faculty of Science, University of Porto, Portugal,
and the University of Leipzig, F.R. of Germany, under
the auspices of the INIDA program (Acßc o~ es Integradas
Luso-Alem ~a s 314-Al-p-dr), between ICTI (Instituto de
Cooperaßc ~a o Cient ꢀı fica e Tecnol oꢀ gica Internacional)
Lisboa, Portugal, and DAAD (Deutscher Akademischer
Austauschdienst), Bonn, Germany, to which we express
our thanks. Thanks are also due to FCT (Fundaßc ~a o
para a Ci ^e ncia e a Tecnologia), Lisboa, Portugal for fi-
nancial support to Centro de Investigaßc ~a o em Qu ꢀı mica,
University of Porto and, for the award of a post-doc
research grant to B.S. (SRFH/BPD/3531/2000).
[
20] W.D. Good, D.W. Scott, in: H.A. Skinner (Ed.), Experimental
Thermochemistry, vol. 2, Interscience, New York, 1962
(Chapter 2).
[21] T.B. Coplen, J. Phys. Chem. Ref. Data 30 (2001) 701–712.
[
22] F.A. Adedeji, D.L.S. Brown, J.A. Connor, M. Leung, M.I. Paz-
Andrade, H.A. Skinner, J. Organomet. Chem. 97 (1975)
2
21–228.
23] L.M.N.B.F. Santos, B. Schr o€ der, O.O.P. Fernandes, M.A.V.
[
Ribeiro da Silva, Thermochim. Acta (in print).
[24] D.R. Stull, E.F. Westrum, G.C. Sinke, The Chemical Thermody-
namics of Compounds, Wiley, New York, 1969.
[
[
[
25] C.G. Kruif, T. Kuipers, J.C. van Miltenburg, R.C.F. Schaake,
G.F. Stevens, J. Chem. Thermodyn. 13 (1981) 1081–1086.
26] F.D. Rossini, in: F.D. Rossini (Ed.), Experimental Thermochem-
istry, vol. 1, Interscience, New York, 1956 (Chapter 14).
27] J.D. Cox, D.D. Wagman, V.A. Medvedev (Eds.), CODATA
Key Values for Thermodynamics, Hemisphere, New York,
1
989.
28] J.D. Cox, G. Pilcher, Thermochemistry of Organic and Organo-
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1] L. L o€ ssner, J. Prakt. Chem. 10 (1874) 235–261.
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[
JCT 04/12