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1.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
The heat capacities (C
p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range
from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at
350.426 K. The melting temperature (T
m), the molar enthalpy (Δfus
H
m0), and the molar entropy (Δfus
S
m0) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation.
The thermodynamic functions (H
T-H
298.15 and S
T-S
298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU
c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc
H
m0 (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
3.
Yu H. G. Yu Dong J. X. Qin C. Q. Liu Y. Qu S. S. 《Journal of Thermal Analysis and Calorimetry》2004,75(3):807-813
The energy of combustion of crystalline 3,4,5-trimethoxybenzoic acid in oxygen at T=298.15 K was determined to be -4795.9±1.3 kJ mol-1 using combustion calorimetry. The derived standard molar enthalpies of formation of 3,4,5-trimethoxybenzoic acid in crystalline
and gaseous states at T=298.15 K, ΔfHm
Θ (cr) and ΔfHm
Θ (g), were -852.9±1.9 and -721.7±2.0 kJ mol-1, respectively. The reliability of the results obtained was commented upon and compared with literature values.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Z. H. Zhang L. X. Sun Z. C. Tan F. Xu X. C. Lv J. L. Zeng Y. Sawada 《Journal of Thermal Analysis and Calorimetry》2007,89(1):289-294
The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature X by polynomial equations, C
p,m [J K−1 mol−1]=181.43+51.297X −4.7816X
2−1.9734X
3+8.1048X
4+11.108X
5 [X=(T−135)/55] for the solid phase (80–190 K), C
p,m [J K−1 mol−1]= 349.96+25.106X+9.1320X
2+19.368X
3+2.23X
4−8.8201X
5 [X=(T−225)/27] for the glass state (198–252 K), and C
p,m[J K−1 mol−1]= 402.40+21.982X−3.0304X
2+3.6514X
3+3.4585X
4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH
g=2.157 kJ mol−1 and ΔS
g=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH
m = 8.453 kJ mol−1 and ΔS
m=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be Δc
H
m0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be Δf
H
m0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K. 相似文献
5.
Griesser U. J. Weigand D. Rollinger J. M. Haddow M. Gstrein E. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):511-522
Five crystal polymorphs of the herbicide metazachlor (MTZC) were characterized by means of hot stage microscopy, differential
scanning calorimetry, IR- and Raman spectroscopy as well as X-ray powder diffractometry. Modification (mod.) I, II and III°
can be crystallized from solvents and the melt, respectively, whereas the unstable mod. IV and V crystallize exclusively from
the super-cooled melt. Based on the results of thermal analysis and solvent mediated transformation studies, the thermodynamic
relationships among the polymorphic phases of metazachlor were evaluated and displayed in a semi-schematic energy/temperature-diagram.
At room temperature, mod. III° (T
fus =76°C, Δfus
H
III =26.6 kJ mol-1) is the thermodynamically stable form, followed by mod. II (T
fus =80°C, Δfus
H
II =23.0 kJ mol-1) and mod. I (T
fus =83°C, Δfus
H
II=19.7 kJ mol-1). These forms are enantiotropically related showing thermodynamic transition points at ~55°C (T
trs, III/II), ~60°C (T
trs, III/I) and ~63°C (T
trs, II/I). Thus mod. I is the thermodynamically stable form above 63°C, mod. III° below 55°C and mod. II in a small window between
these temperatures. Mod. IV (T
fus =72-74°C, Δfus
H
II =18.7 kJ mol-1) and mod. V (T
fus =65°C) are monotropically related to each other as well as to all other forms. The metastable mod. I and II show a high kinetic
stability. They crystallize from solvents, and thus these forms can be present in commercial samples. Since metazachlor is
used as an aqueous suspension, the use of the metastable forms is not advisable because of a potential transformation to mod.
III°. This may result in problematic formulations, due to caking and aggregation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
M.-H. Wang Z.-C. Tan Q. Shi L.-X. Sun T. Zhang 《Journal of Thermal Analysis and Calorimetry》2006,84(2):413-418
The
heat capacities of 2-benzoylpyridine were measured with an automated adiabatic
calorimeter over the temperature range from 80 to 340 K. The melting point,
molar enthalpy, ΔfusHm,
and entropy, ΔfusSm,
of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03
kJ mol–1 and 66.07±0.05 J mol–1
K–1, respectively. The purity of the compound
was calculated to be 99.60 mol% by using the fractional melting technique.
The thermodynamic functions (HT–H298.15) and (ST–S298.15) were calculated based
on the heat capacity measurements in the temperature range of 80–340
K with an interval of 5 K. The thermal properties of the compound were further
investigated by differential scanning calorimetry (DSC). From the DSC curve,
the temperature corresponding to the maximum evaporation rate, the molar enthalpy
and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2
kJ mol–1 and 92.2±0.4 J K–1
mol–1, respectively, under the experimental
conditions. 相似文献
7.
N. B. Morozova P. P. Semyannikov S. V. Sysoev V. M. Grankin I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2000,60(2):489-495
The temperature dependency of the saturated vapor pressure of Ir(acac)3 has been measured by the method of calibrated volume (MCV), the Knudsen method, the flow transpiration method, and the membrane
method. The thermodynamic parameters of phase transition of a crystal to gas were calculated using each of these methods,
and the following values of ΔH
T
0 (kJ mol−1) and ΔS
T
0 (J mol−1K−1), respectively, were obtained: MCV: 101.59, 156.70; Knudsen: 130.54, 224.40; Flow transpiration: 129.34, 212.23; Membrane:
95.45, 149.44
Coprocessing of obtaining data (MCV, flow transportation method and Knudsen method) at temperature ranges 110−200°C as also
conducted:ΔH
T
0 =127.9±2.1 (kJ mol−1 ); ΔS
T
0 =215.2±5.0 (J mol−1 K−1 ).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Xue B. Wang J.-Y. Tan Z.-C. Lu S.-W. Meng S.-H. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):965-973
The heat capacities of chrysanthemic acid in the temperature range from 80 to 400 K were measured with a precise automatic
adiabatic calorimeter. The chrysanthemic acid sample was prepared with the purity of 0.9855 mole fraction. A solid-liquid
fusion phase transition was observed in the experimental temperature range. The melting point, T
m, enthalpy and entropy of fusion, Δfus
H
m, Δfus
S
m, were determined to be 390.741±0.002 K, 14.51±0.13 kJ mol-1, 37.13±0.34 J mol-1 K-1, respectively. The thermodynamic functions of chrysanthemic acid, H
(T)-H(298.15), S
(T)-S(298.15) and G
(T)-G
(298.15) were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min-1 confirmed that the thermal decomposition of the sample starts at ca. 410 K and terminates at ca. 471 K. The maximum decomposition
rate was obtained at 466 K. The purity of the sample was determined by a fractional melting method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Wang S. X. Tan Z. C. Di Y. Y. Xu F. Wang M. H. Sun L. X. Zhang T. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):335-342
As one primary component of Vitamin B3, nicotinic acid [pyridine 3-carboxylic acid] was synthesized, and calorimetric study and thermal analysis for this compound
were performed. The low-temperature heat capacity of nicotinic acid was measured with a precise automated adiabatic calorimeter
over the temperature rang from 79 to 368 K. No thermal anomaly or phase transition was observed in this temperature range.
A solid-to-solid transition at T
trs=451.4 K, a solid-to-liquid transition at T
fus=509.1 K and a thermal decomposition at T
d=538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be
Δtrs
H
m=0.81 kJ mol-1, Δfus
H
m=27.57 kJ mol-1 and Δd
H
m=62.38 kJ mol-1, respectively, by the integrals of the peak areas of the DSC curves.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
B. Tong Z. C. Tan J. N. Zhang S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):469-475
The low-temperature heat capacity C
p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C
p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard
molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc
H
m0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf
H
m0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement
with those obtained from heat capacity measurements. 相似文献
11.
Ladislav Kosa Iveta Macková Ivo Proks Ondrej Pritula Ľubomír Smrčok Miroslav Boča Håkan Rundlőf 《Central European Journal of Chemistry》2008,6(1):27-32
Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change
of the individual processes are: ΔtransIIHm(K2TaF7; 703°C) = 1.7(2) kJ mol−1, ΔtransIHm(K2TaF7; 746°C) = 19(1) kJ mol−1 and ΔtransIIIHm(K2TaF7; 771°C) = 13(1) kJ mol−1. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.
相似文献
12.
F. Xu L.-X. Sun Z.-C. Tan J.-G. Liang Y.-Y. Di Q.-F. Tian T. Zhang 《Journal of Thermal Analysis and Calorimetry》2004,76(2):481-489
Molar heat capacities (C
p,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range
from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of C
p,m
vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding
function is as follows: for 78 K≤T≤383 K, C
p,m/J mol-1 K-1=19.086X
4+15.951X
3-5.2548X
2+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔH
T -ΔH
298.15} and {S
T-S
298.15}, were derived. Combustion energy of aspirin (Δc
U
m) was determined by static bomb combustion calorimeter. Enthalpy of combustion (Δc
H
o
m) and enthalpy of formation (Δf
H
o
m) were derived through Δc
U
m as - (3945.26±2.63) kJ mol-1 and - (736.41±1.30) kJ mol-1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Stefan Perişanu Iulia Contineanu Mircea D. Banciu Hui Zhao Nigam Rath James Chickos 《Structural chemistry》2006,17(6):639-648
Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol−1, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol−1) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol−1) adjusted from DSC measurements at the melting temperature (1, (T
fus, 357.7 K, 16.9 ± 1.3 kJ mol−1)); 2, (T
fus, 383.3 K, 10.9 ± 0.1) kJ mol−1) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol−1) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol−1) and 7-heptadecanone ((94.5 ± 1.8) kJ mol−1) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T
fus, 312.7 K, 18.4 ± 0.5) kJ mol−1) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound
1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone. 相似文献
14.
S. Vecchio 《Journal of Thermal Analysis and Calorimetry》2007,87(1):79-83
The vaporization enthalpies of two acetanilide pesticides, alachlor
(2’,6’-diethyl-N-(methoxymethyl)-2-chloroacetanilide) and metolachlor
(2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl] acetamide),
were determined by processing non-isothermal thermogravimetry data according
to the Clausius-Clapeyron equation. The reliability of the procedure proposed
was tested carrying out some experiments at different heating rates using
acetanilide as a reference compound. A good agreement is found among the vaporization
enthalpies derived from all the multi-heating rate experiments as well as
with the one predicted from the vapor pressure data taken from literature.
The vaporization temperatures (T
vap=470±2
K and T
vap=479±2
K) and enthalpies (Δvap
H°(436
K)=85±1 kJ mol–1 and Δvap
H°(436 K)=70±1 kJ mol–1)
for alachlor and metolachlor, were selected, respectively. 相似文献
15.
Thermochemical
studies on the thioproline 总被引:3,自引:0,他引:3
The combustion energy of thioproline was determined
by the precision rotating-bomb calorimeter at 298.15 K to be Δc
U= –2469.30±1.44 kJ mol–1.
From the results and other auxiliary quantities, the standard molar enthalpy
of combustion and the standard molar enthalpy of formation of thioproline
were calculated to be Δc
H
m
θC4H7NO2S,
(s), 298.15 K= –2469.92±1.44 kJ mol–1
and Δf
H
m
θC4H7NO2S, (s), 298.15K= –401.33±1.54
kJ mol–1. 相似文献
16.
Hermínio P. Diogo Joaquim J. Moura Ramos 《Journal of Thermal Analysis and Calorimetry》2013,111(1):773-779
The thermally stimulated depolarization current (TSDC) technique has been used to study the slow molecular mobility of polysulfone in the glassy state and in the glass transformation region, i.e., in the temperature ranging from ?155 to 183 °C. Since the polysulfone is a rigid polymer without polar side-groups, a broad and low-intensity secondary relaxation was detected in the temperature region from ?120 °C up to the glass transition; the activation energy of the motional modes of this secondary relaxation is in the range between 35 and 100 kJ mol?1. The glass transition temperature of polysulfone provided by the TSDC technique is T M = T g = 176 °C (at 4 °C min?1). The relaxation time at this temperature is τ(T g) = 33 s and the fragility index was found to be m = 91. Our results are compared with literature values obtained by dynamic mechanical analysis and by dielectric relaxation spectroscopy. The amorphous polysulfone was also characterized by DSC; a glass transition signal with an onset at T on = 185.5 ± 0.3 °C (heating rate 10 °C min?1) was detected, with ΔC p = 0.21 ± 0.01 J g?1 °C?1. 相似文献
17.
M. A. V. Ribeiro da Silva C. P. F. Santos M. J. S. Monte C. A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2006,83(3):533-539
The
standard (p0=0.1
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.0±1.7), – (350.1±2.7) and – (377.3±2.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.9±1.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.3±1.3), (91.0±1.2) and (98.2±1.4)
kJ mol–1.
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure. 相似文献
18.
Pena R. Chauvet A. Masse J. Ribet J. P. Maurel J. L. 《Journal of Thermal Analysis and Calorimetry》1998,53(3):697-709
The phase diagram of R(+)-S(-) efaroxan hydrochloride (Tfus.(R)=245.1±0.3°C. ΔHfus.(R)=119.6±3.0 J g-1) shows a racemic compound. The melting temperature and melting enthalpy of the compound are: Tfus.(RS)=247.8±0.2°C and ΔHfus. (RS)=124.6±2.4 J g-1. A solid ↔ solid transformation takes place at Ttrs.=180±1°C, ΔHtrs.=15.0±0.4 J g-1. This transition is observed between 3 and 97% R(+). The stability of the racemic compound already established in a previous
study was confirmed by the value of Petterson's coefficient (i=1.19). The two eutectic positions at 20 and 80% R(+) that define
the range over which the racemic compound is found, exclude the use of resolution methods by preferential crystallization.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
M. A. V. Ribeiro da Silva Cláudia P. F. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(1):21-25
The standard (p
0=0.1
MPa) molar enthalpy of formation, Δf
H
0
m, for crystalline N-phenylphthalimide
was derived from its standard molar enthalpy of combustion, in oxygen, at
the temperature 298.15 K, measured by static bomb-combustion calorimetry,
as –206.0±3.4 kJ mol–1. The
standard molar enthalpy of sublimation, Δg
cr
H
0
m
, at T=298.15 K, was derived, from high
temperature Calvet microcalorimetry, as 121.3±1.0 kJ mol–1.
The derived standard molar enthalpy of formation, in the gaseous state,
is analysed in terms of enthalpic increments and interpreted in terms of molecular
structure. 相似文献
20.
G. Xie S. P. Chen S. L. Gao X. X. Meng Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):693-700
A novel solid complex, formulated as Ho(PDC)3
(o-phen), has been obtained from the reaction
of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and
1,10-phenanthroline (o-phen·H2O)
in absolute ethanol, which was characterized by elemental analysis, TG-DTG
and IR spectrum. The enthalpy change of the reaction of complex formation
from a solution of the reagents, ΔrHmθ (sol), and the molar heat capacity of the complex, cm,
were determined as being –19.161±0.051 kJ mol–1
and 79.264±1.218 J mol–1 K–1
at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy
change of complex formation from the reaction of the reagents in the solid
phase, ΔrHmθ(s), was calculated as
being (23.981±0.339) kJ mol–1 on the
basis of an appropriate thermochemical cycle and other auxiliary thermodynamic
data. The thermodynamics of reaction of formation of the complex was investigated
by the reaction in solution at the temperature range of 292.15–301.15
K. The constant-volume combustion energy of the complex, ΔcU, was determined as being –16788.46±7.74
kJ mol–1 by an RBC-II type rotating-bomb
calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHmθ, and standard enthalpy of formation,
ΔfHmθ, were calculated to be –16803.95±7.74 and –1115.42±8.94
kJ mol–1, respectively. 相似文献