Low-temperature heat capacity and standard molar enthalpy of formation of 9-fluorenemethanol (C14H12O)

Article abstract of DOI:10.1016/j.jct.2003.08.017

Low-temperature heat capacities of the 9-fluorenemethanol (C ₁₄H₁₂O) have been precisely measured with a small sample automatic adiabatic calorimeter over the temperature range between T = 78 K and T = 390 K. The solid-liquid phase transition of the compound has been observed to be T_fus = (376.567 ± 0.012) K from the heat-capacity measurements. The molar enthalpy and entropy of the melting of the substance were determined to be Δ_fusH_m = (26.273 ± 0.013) kJ · mol^-1 and Δ_fusS_m = (69.770 ± 0.035) J · K^-1·mol^-1. The experimental values of molar heat capacities in solid and liquid regions have been fitted to two polynomial equations by the least squares method. The constant-volume energy and standard molar enthalpy of combustion of the compound have been determined, Δ_cU(C₁₄H ₁₂O, s) = -(7125.56 ± 4.62) kJ·mol^-1 and Δ_cH_m^°(C₁₄H₁₂ O, s) = -(7131.76 ± 4.62) kJ · mol^-1 by means of a homemade precision oxygen-bomb combustion calorimeter at T = (298.15 ± 0.001) K. The standard molar enthalpy of formation of the compound has been derived, Δ_f H_m^°(C₁₄H ₁₂ O, s) = -(92.36 ± 0.97) kJ · mol^-1, from the standard molar enthalpy of combustion of the compound in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

Full text of DOI:10.1016/j.jct.2003.08.017

J. Chem. Thermodynamics 36 (2004) 79–86
www.elsevier.com/locate/jct
Low-temperature heat capacity and standard molar enthalpy
of formation of 9-fluorenemethanol (C14H12O)
a
a,
b
a
a
You-Ying Di , Zhi-Cheng Tan *, Xiao-Hong Sun , Mei-Han Wang , Fen Xu ,
b
a
Yuan-Fa Liu , Li-Xian Sun , Hong-Tao Zhang
a
a
Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China
b
College of Chemical Engineering, Northwest University, Xi’an 710069, PR China
Received 13 June 2003; accepted 18 August 2003
Abstract
Low-temperature heat capacities of the 9-fluorenemethanol (C14H12O) have been precisely measured with a small sample au-
tomatic adiabatic calorimeter over the temperature range between T ¼ 78 K and T ¼ 390 K. The solid–liquid phase transition of the
compound has been observed to be Tfus ¼ ð376:567 ꢀ 0:012Þ K from the heat-capacity measurements. The molar enthalpy and
entropy of the melting of the substance were determined to be DfusHm ¼ ð26:273 ꢀ 0:013Þ kJ ꢁ molꢂ1 and DfusSm ¼ ð69:770 ꢀ 0:035Þ
J ꢁ Kꢂ1 ꢁ molꢂ1. The experimental values of molar heat capacities in solid and liquid regions have been fitted to two polynomial
equations by the least squares method. The constant-volume energy and standard molar enthalpy of combustion of the compound
have been determined, DcU(C14H12O, s) ¼ ꢂ(7125.56 ꢀ 4.62) kJ ꢁ molꢂ1 and DcHmꢃ (C14H12O, s) ¼ ꢂ(7131.76 ꢀ 4.62) kJ ꢁ molꢂ1, by
means of a homemade precision oxygen-bomb combustion calorimeter at T ¼ ð298:15 ꢀ 0:001Þ K. The standard molar enthalpy of
formation of the compound has been derived, Df Hmꢃ (C14H12O, s) ¼ ꢂ(92.36 ꢀ 0.97) kJ ꢁ molꢂ1, from the standard molar enthalpy of
combustion of the compound in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: 9-Fluorenemethanol; Adiabatic calorimetry; Low-temperature heat capacity; Enthalpy of fusion; Standard molar enthalpy of combustion;
Standard molar enthalpy of formation
1. Introduction
The 9-fluorenemethanol (CAS No.: 24324-17-2) is an
important chemical raw material and intermediate in the
preparation of many medicines, germicides, herbicides,
insecticides and growth regulator of plant. Especially, it
the compound is a white crystal with a needle-like shape
is widely used to synthesize 9-fluorenemethyl chloro-
The literature [1,2] has reported that the appearance of
and the melting point is T ¼ (375 to 377) K. With the
formic ester (abbreviated as Fmoc-Cl) and 9-fluore-
nemethyl-N-amber imino carbonate (abbreviated as
Fmoc-OSU), which are the N-protecting reagents for the
amino groups in many organic compounds as the in-
development of the pharmaceutical industry and the wide
application of the polypeptides, many new fields in which
the compound is involved are found and the demand for
the 9-fluorenemethanol is greatly increased. However, up
termediates and play an distinctive role in the synthesis
till now, the fundamental thermodynamic data of the
of many polypeptide medicines. The molecular formula
compound have not been reported in the literature. For
of 9-fluorenemethanol is C14H12O, the molar mass is
196.2482 g ꢁ molꢂ1 and the molecular structure is
the purposes of further investigation and application of
the substance, in the present work, low-temperature heat
capacities over the temperature range between T ¼ 78 K
* Corresponding author. Fax: +86-411-4691570.
E-mail address: tzc@dicp.ac.cn (Z.-C. Tan).
and T ¼ 390 K and the standard molar enthalpies of
combustion at T ¼ 298:15 K were measured by adiabatic
0021-9614/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jct.2003.08.017

80
Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
calorimetry and oxygen-bomb combustion calorimetry,
respectively. The melting point, the enthalpy and entropy
of fusion of the compound have been determined from the
fractional melting method based on the results of the heat-
capacity measurements.
to be T ¼ (376.3 to 377.7) K with a microscopic melting
point device (model: BY-1, Yazawa Co., Japan), and in
agreement with that of the literature [1,2]. The actual
purity of the sample was determined to be higher than
0.9990 mole fraction by HPLC (Shimadzu, model: LC-
10AT, Japan) analysis and no impurity was detected.
The elementary analysis (model: 1106, made in Italy)
has indicated that the contents of C and H elements in
the sample were 85.66% and 6.15%, respectively, which
were identical with the theoretical contents of the H and
C elements in the compound, 85.68% and 6.16%. The
contents of the impurity elements were within the de-
tection limit of the elementary analyzer. The IR (model:
260-10, made by HITACHI, Japan) showed character-
istic absorption peaks at 3405, 3063, 2919, 2860, 1460,
1450, 1360, 1310, 1280, 1170, 1050, 1030, 1005, 930, 840,
750, 730, 720, 593, 530, 425 cmꢂ1. The 1H NMR (model:
Unity Plus 500, made by Varian Ltd., USA, CDCl3)
absorption peaks agreed with those of the literature [2].
The oxygen-bomb combustion calorimeter is one of
the basic devices necessary for some thermochemical
research, especially useful for the determination of the
combustion energies of some elements, organic com-
pounds and metallorganics, etc. The combustion calo-
rimetry is often applied to determine the standard molar
enthalpies of formation of many important organic
substances in industry and scientific research based on
the data of enthalpies of combustion and some auxiliary
thermodynamic quantities. The standard molar enthal-
pies of formation, together with the standard or speci-
fied entropy, are equally important data in determining
any chemical equilibrium. In the present paper, a precise
and computer-controlled isoperibol oxygen-bomb com-
bustion calorimeter suitable for investigating combus-
tion enthalpies of many novel compounds is described in
more detail on the basis of other commercial apparatus
[3–6] and our previous works [7,8]. The standard molar
enthalpy of formation of the 9-fluorenemethanol has
been derived from the combination of the result of the
standard molar enthalpy of combustion with other
auxiliary thermodynamic quantities.
2.2. Adiabatic calorimetry
A precision automatic adiabatic calorimeter was ap-
plied to measure the heat capacities over the tempera-
ture range between T ¼ 78 K and T ¼ 390 K. The
calorimeter was established in Thermochemistry Labo-
ratory of Dalian Institute of Chemical Physics, Chinese
Academy of Sciences in PR China. The principle and
structure of the adiabatic calorimeter were described in
detail elsewhere [9–11]. Briefly, the calorimeter was
mainly composed of a sample cell, a miniature platinum
resistance thermometer, an electric heater, the inner and
the outer adiabatic shields, two sets of six-junctions
chromel–constantan thermopiles installed between the
calorimetric cell and the inner shield and between the
inner and outer shields, respectively, and a high vacuum
can. The sample cell was made of gold-plated copper
and had an inner volume of 0.006 dm3. Four gold-plated
copper vanes of 0.2 mm in thickness with a X-shape
were placed into the cell to promote heat distribution in
the sample cell. The miniature platinum resistance
thermometer (IPRT No. 2, produced by Shanghai In-
stitute of Industrial Automatic Meters, 16 mm in length,
1.6 mm in diameter and a nominal resistance of 100 X)
was used to measure the temperature of the sample. The
thermometer was calibrated on the basis of ITS-90 by
the Station of Low-temperature Metrology and Mea-
surements, Academia Sinica. The thermometer was in-
serted into the copper sheath which was silver-soldered
closely at the bottom of the sample cell. The heater wire
was bifilarly wound and fixed on the side surface of the
cell. The lid of the cell with a copper capillary was sealed
to the sample cell with adhesive after the sample was
loaded. The air in the cell was evacuated and a small
amount of helium gas (0.1 MPa) was introduced to en-
hance the heat transfer in the cell. The capillary was
2. Experimental
2.1. Sample synthesis and characterization
The 9-fluorenemethanol was prepared according to
the procedure given in the literature [2]. The fluorene
(A.R.) was chosen as the crude material, the potassium
ethylate (A.R.) was used as the solid–liquid phase
transfer catalyst and the ethyl formate (A.R.) as the
solvent in the synthesis of the sample. The whole prep-
aration was completed by the following two-step reac-
tions:
The crude product was a pale yellow powder. It was
recrystallized three times with petroleum ether of ana-
lytical grade. The final product was a white needle-like
crystal. The melting point of the sample was determined

Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
81
pinched off from the end away from the lid and soldered.
2.3. Oxygen-bomb combustion calorimetry
The temperature differences between the sample cell and
the inner shield and between the inner and outer shields
were monitored by the two sets of thermopiles, and
controlled by two sets of DWT-702 precision tempe-
rature controllers (manufactured by Shanghai No. 6
Automated Instrumentation Works). When the tem-
perature of the sample cell increases due to heating, the
differential thermocouples measure the temperature
differences. This signal is used to control the heaters
distributed on the walls of the inner and outer shields,
respectively. Both shields were heated under the control
of the signal and kept at the same temperatures as that
of the sample cell. At the same time, the vacuum can
where the sample cell housed was evacuated to be 10ꢂ3
Pa. In this way, the heat loss of the sample cell caused by
the radiation and convection is greatly reduced. The
sensitivity for the measurements of the electrical voltage
through the heater of sample cell was ꢀ0.1 lV. The
electrical energy introduced into the sample cell and the
equilibrium temperature of the cell after the energy in-
put were automatically picked up by use of the Data
Acquisition/Switch Unit (Model 34970A, Agilent,
USA), and processed on line by a computer.
The constant-volume energy of combustion of the
sample was measured by means of a homemade preci-
sion oxygen-bomb combustion calorimeter. It was an
isoperibolic macrocalorimeter with a static oxygen
bomb and set up in our thermochemistry laboratory.
The structure and principle of the calorimeter have been
described previously in brief [7,8]. The schematic dia-
gram of the isoperibol oxygen-bomb combustion calo-
rimeter is shown in figure 1. It consisted of a static
oxygen bomb, inner calorimetric vessel, outer thermo-
static bath, platinum resistance thermometer, precision
temperature controller, ignition system and temperature
measurement system. The oxygen bomb was made from
a special stainless steel with good heat conduction. The
efficient volume of the bomb was about 0.3 dm3. Two
stainless steel ignition electrodes of 0.8 cm in diameter
were extended to the centre of the bomb downright from
the lid of the bomb. The two ignition electrodes were
installed in the lid of the bomb and linked with the ig-
nition system. They had a good electrical insulation
from the lid to eliminate the effect of the electric current
of the ignition on the temperature measurements. Ex-
cept for the two ignition electrodes, a filling-oxygen
valve was also mounted in the lid. A small sample cru-
cible of about 0.004 dm3 was hanged in the bomb by
means of a horizontal ring. The ring was vertically fixed
on one of the two stainless steel electrodes and in a good
electric contact with the sample crucible. The second
electrode was not directly coupled with the ring, but in a
good electrical contact with the first electrode through
the ignition nickel fuse. The nickel fuse in the form of
the coil in its middle was tightly pressed on the sample
after a pellet of sample was horizontally put in the
sample crucible. The oxygen bomb was immersed in
2.850 dm3 of the deionized water contained in the inner
calorimetric vessel during the whole combustion. The
total mass of both inner calorimetric vessel and deion-
ized water was 3900 g. The deionized water in the inner
calorimetric vessel was stirred at a uniform rate of 150
rotations per minute so that heat released in the oxygen
bomb was rapidly absorbed by the deionized water and
the heat leakage from the inner calorimetric vessel to the
surroundings was reduced to the minimum level during
the combustion test.
To verify the accuracy of the calorimeter, the heat-
capacity measurements of the reference standard mate-
rial, a-Al2O3, were made over the temperature range
78 6 (T/K) 6 400. The sample mass used was 1.6382 g,
which was equivalent to 0.0161 mol based on its molar
mass, M(Al2O3) ¼ 101.9613 g ꢁ molꢂ1. Deviations of the
experimental results from those of the smoothed curve
lie within ꢀ0.2%, while the inaccuracy is within ꢀ0.3%,
as compared with those of the former National Bureau
of Standards [12] over the whole temperature range.
Heat-capacity measurements were continuously and
automatically carried out by means of the standard
method of intermittently heating the sample and alter-
nately measuring the temperature. The heating rate and
temperature increments were generally controlled at (0.1
to 0.4) K ꢁ minꢂ1 and (1 to 4) K. The energy introduced
into the sample cell was supplied by a d.c. voltage sup-
plier with a stability of 5 ꢁ 10ꢂ6. The heating duration
was 10 min, and the temperature drift rates of the
sample cell measured in an equilibrium period were al-
ways kept within (10ꢂ3 to 10ꢂ4) K ꢁ minꢂ1 during the
acquisition of all heat-capacity data. In order to obtain
good adiabatic conditions between the calorimetric cell
and its surroundings, the temperature difference between
the calorimetric cell and the inner shield was automati-
cally kept within 1 mK during the whole experiment.
The data of heat capacities and corresponding equilib-
rium temperature have been corrected for heat exchange
of the sample cell with its surroundings [9–11]. The
sample mass used for calorimetric measurements was
2.0981 g, which was equivalent to 0.010691 mol in terms
The system of controlling the temperature was com-
posed of a thermostatic bath, an electric stirrer, an
electric heater, a precision temperature controller and a
Cu 50 resistance thermometer. The thermostatic bath
was made from the stainless steel plate of 5 mm in
thickness, on the surface of which the thermal insulation
paint was coated. The volume of the bath was about 60
dm3. The thermostatic medium is the distilled water to
protect the inner calorimetric vessel from the corrosion.
The Cu 50 resistance thermometer was used to measure
of its molar mass, M ¼ 196:2482 g ꢁ molꢂ1
.

82
Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
Personal
computer
Temperature
controller
Wheatstone
bridge
Agilent
34970
A
Temperature
measurement
Ignition
supply
Water Cooler
B
C
D
E
F
G
H
I
J
K
L
FIGURE 1. The schematic diagram of an isoperibol oxygen-bomb combustion calorimeter (A – electric motor; B – Cu 50 resistance thermometer;
C – oxygen-filling valve; D – ignition electrodes; E – heater; F – oxygen bomb; G – stirrers; H – Pt resistance thermometer; I – sample crucible; J –
inner calorimetric vessel; K – thermal shield; L – water thermostat).
the temperature of the water in thermostatic bath. The
inner calorimetric vessel was located at the centre of the
outer thermostatic bath and completely immersed in
the thermostatic water of the outer bath. The oxygen
bomb was put in the centre of the inner calorimetric
vessel. There was an air jacket of 2.5 cm in thickness
between the inner calorimetric vessel and the outer
thermostatic bath so as to increase the thermal insulation
of the calorimetric system. The temperature of the water
in the outer thermostatic bath was controlled by means
of a precision temperature controller (model: AL-708,
made in Yuguang institute of electronic technology,
Xiamen, PR China). The Cu 50 thermometer and the
electric heater were linked with the temperature con-
troller through a precision electric bridge. The thermo-
static water was stirred by an electric stirrer at a rate of
240 rotations per minute. Measurements have shown that
the precision of controlling the temperature for the
thermostatic system can at least reach ꢀ0.001 K.
The temperature measurement system consisted of a
precision platinum resistance thermometer and a Data
Acquisition/Switch Unit (Model 34970A, Agilent,
USA). The temperature of the water in the inner calo-
rimetric vessel of the calorimeter was measured by the
precision platinum resistance thermometer (PTU 5ꢄ 40,
40 mm in length, 5 mm in diameter; R0 ¼ 196:9865X,
made by the Instrument Manufacture Co. of Yunnan,
PR China). The thermometer was calibrated on the
basis of ITS-90 by the National Institute of Metrology
(NIM). The thermometer was linked in four leads with
two interfaces of the Agilent Data Acquisition/Switch
Unit to measure the temperatures of the calorimetric
system through a program on line by a personnel
computer.

Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
83
The correction of the temperature rise (1) was ob-
tained from the following formula [13,14]:
The measurement was composed of initial (10 min),
combustion (15 min) and final (10 min) periods. The
data acquisition starts automatically when the temper-
ature of the calorimeter reached the equilibrium point of
controlling the temperature at T ¼ ð298:15 ꢀ 0:001Þ K.
In each period, all the voltage values across the platinum
resistance thermometer and the standard resistance
ðRN ¼ 100:053XÞ connected in series with the ther-
mometer, Ep and EN were collected at the same time at
the interval of 30 s by using the Agilent Data Acquisi-
tion/Switch Unit, and the corresponding temperatures
were calculated on line according to the calibrated pa-
rameters of the thermometer by a personnel computer.
The sample was ignited at 600 s from the start of data
acquisition. After each run, the combustion products
were analyzed mainly for carbon dioxide by the Rossini
method [15]. No soot was observed in the sample cru-
cible after combustion experiments of the 9-fluorene-
methanol. Qualitative tests for CO with indicator tubes
were negative within the limits of their sensitivity {mole
fraction x (CO) < 1 ꢁ 10ꢂ6g.
!
ꢀ
ꢁ
Tf
X
Vn ꢂ V0
hn ꢂ h0
T0 þ Tf
1 ¼
ꢁ
þ
Ti ꢂ nhn þ nVn
2
T0
in which Vn/K ꢁ minꢂ1 is the temperature drift rate in the
final period; V0/K ꢁ minꢂ1, the temperature drift rate in
the initial period; hn/K, the average temperature of the
calorimeter during the final period; h0/K, the average
temperature of the calorimeter during the initial period;
T0/K, the last reading of the temperatures in the initial
period; Tf /K, the first reading of the temperatures in the
final period; n, the number of readings for the reaction
or main period; the corrected temperature rise of the
combustion or reaction is: DT ¼ ðTf ꢂ T0Þ þ 1.
The ignition system was composed of a transformer
and an electric switch. The voltageof the transformer used
in the ignition was set at about 25 V. The length of the
ignition nickel wire used in each of combustion tests was
about 16 cm. The resistance of the ignition nickel fuse was
about 7 X. The electric energy for the ignition was deter-
mined from the change in potential difference across a
capacitor when discharged through the nickel wire to be
0.89 J.
The energy equivalent, ecalor, of the calorimeter has
been determined from 10 combustion experiments using
about 0.7 g of NIST 39i benzoic acid with a certified
massic energy of combustion under experimental con-
The sample was pressed into pellets of (0.6 to 1.0) g
for each combustion and burned under an oxygen
pressure of 3.01 MPa in the presence of 0.001 dm3 of
distilled water in the bomb to ensure equilibrium in the
final state after the combustion. The purity of the oxy-
gen used in the experiment was of research grade, mole
fraction 0.99998. The mass of the sample has been cal-
ibrated from the air buoyancy on the basis of the de-
termination of the density for a pellet of the sample. At
the T ¼ ð298:15 ꢀ 0:001Þ K, the differential quotient of
the constant-volume energy of combustion with the
oxygen pressure, ðoU=oPÞT , for these solids was as-
sumed to be ꢂ0.21 J ꢁ gꢂ1 ꢁ MPaꢂ1, a typical value for
organic solids. The standard energy of combustion of
the nickel fuse for ignition has been determined previ-
ously to be DcU°/J ꢁ cmꢂ1 ¼ 2.929. The real energy of
combustion of the nickel fuse ðQNiÞ was calculated from
the formula, QNi/J ¼ 2.929 ꢁ DL, in which DL/cm was the
length of the combusted nickel wire. The correction for
the energy of formation of aqueous nitric acid, produced
by oxidation of a trace of nitrogen contained in the
oxygen bomb, was determined by the neutral titration
with a 0.1000 mol ꢁ dmꢂ3 of sodium hydroxide solution
by using the methyl orange as the indicator. The heat of
formation of the aqueous nitric acid in the oxygen bomb
ditions of DcU ¼ ꢂð26434 ꢀ 3Þ J ꢁ gꢂ1 to be: ecalor
¼
ð13572:22 ꢀ 0:98Þ J ꢁ Kꢂ1. The uncertainty of the results
was the standard deviation of the mean value from the
respective measurements.
3. Results and discussion
3.1. Heat capacity
All heat-capacity experimental results, listed in table
1 and plotted in figure 2, showed that the structure of
the compound was stable: no phase change occurred in
the solid phase, nor did association or thermal decom-
position occur in the liquid phase (T < 390 K). The
experimental values of the heat capacities have been
fitted to polynomial equations by means of the least
squares method.
For the solid phase
C
p;m=J ꢁ Kꢂ1 ꢁ molꢂ1 ¼ 188:364 þ 128:923X ꢂ 15:187X2ꢂ
30:653X3 þ 53:622X4þ
51:590X5 ꢂ 4:7824X6;
where X ¼ ðT ꢂ 220:5Þ=142:5. The above equation is
valid in the temperature range from T ¼ 78 K to
T ¼ 363 K, with an uncertainty of ꢀ0.50%.
For the liquid phase
can be derived from the equation, QHNO =J ¼ 59:8 ꢁ Nꢁ
3
V , in which N/mol ꢁ dmꢂ3 is the concentration of the
sodium hydroxide solution and V /cm3 is the volume of
the consumed sodium hydroxide solution, based on the
molar energy of formation of HNO3(aq) from N2(g),
O2(g) and H2O(l), Df Hmꢃ ¼ 59.8 kJ ꢁ molꢂ1 [5,6], for 0.1
mol ꢁ dmꢂ3 of HNO3(aq).
C
p;m=J ꢁ Kꢂ1 ꢁ molꢂ1 ¼ 439:958 þ 24:319X þ 1:4348X2ꢂ
1:3644X3 ꢂ 3:2919X4;

84
Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
TABLE 1
Experimental molar heat capacities of the 9-fluorenemethanol (M ¼ 196.2482 g ꢁ molꢂ1) (R ¼ 8:314472 J ꢁ molꢂ1 ꢁ K
ꢂ1
a
)
T/K
C
p;m/R
T/K
C
p;m/R
T/K
Cp;m/R
78.503
8.9715
9.0972
9.2874
9.4944
9.5937
9.7056
9.8260
9.9486
184.317
186.346
188.375
190.323
192.271
194.219
196.168
198.116
200.064
201.931
203.879
205.745
207.694
209.561
211.427
213.213
215.079
216.947
218.732
220.518
222.385
224.171
225.956
227.661
229.447
231.151
232.856
234.642
236.346
238.051
239.755
241.459
243.083
244.706
246.411
248.116
249.739
251.362
253.067
254.691
256.314
257.937
259.560
261.184
262.726
264.349
265.973
267.596
269.138
270.681
272.142
18.652
18.842
19.056
19.248
19.455
19.659
19.849
20.089
20.256
20.462
20.699
20.927
21.141
21.386
21.597
21.808
22.039
22.256
22.431
22.659
22.905
23.139
23.362
23.551
23.773
23.946
24.185
24.391
24.518
24.724
24.912
25.105
25.262
25.405
25.533
25.706
25.866
26.041
26.246
26.421
26.561
26.672
26.849
26.975
27.150
27.291
27.466
27.626
27.798
27.956
28.116
273.684
276.768
280.827
284.155
287.888
291.216
294.463
297.547
300.713
303.797
306.963
310.047
313.051
316.135
319.219
322.223
325.226
328.229
331.151
334.073
336.995
339.836
342.677
345.437
348.034
350.713
353.311
355.989
358.586
360.941
363.781
366.622
369.301
371.898
374.008
375.307
375.956
376.281
376.362
376.444
376.536
376.545
376.606
377.174
378.409
379.627
381.412
383.586
385.714
387.581
389.692
28.274
28.559
28.922
29.269
29.637
29.905
30.316
30.679
31.061
31.457
31.901
32.279
32.725
33.137
33.596
34.039
34.579
35.196
35.830
36.476
37.093
37.794
38.496
39.268
39.965
40.726
41.462
42.231
42.976
43.667
45.345
50.364
66.446
94.727
79.899
82.262
84.642
85.940
87.239
88.538
89.836
91.054
92.271
10.034
10.143
10.277
10.444
10.626
10.775
10.921
11.066
11.220
11.351
11.493
11.713
11.949
12.159
12.397
12.635
12.888
13.157
13.363
13.585
13.759
14.013
14.219
14.462
14.665
14.853
15.102
15.307
15.546
15.740
15.930
16.144
16.368
16.552
16.746
16.960
17.162
17.352
17.557
17.779
17.986
18.195
18.434
93.814
95.682
97.466
99.252
101.038
102.742
104.447
106.151
107.775
110.047
112.807
115.567
118.245
120.843
123.441
126.038
128.554
131.071
133.505
135.941
138.375
140.729
143.083
145.437
147.791
150.063
152.336
154.609
156.801
158.992
161.184
163.375
165.567
167.677
169.869
171.979
174.089
176.119
178.229
180.258
182.288
157.64
377.43
890.43
1793.8
3882.9
4331.9
4417.4
4429.8
2318.9
729.28
50.199
50.758
51.751
52.704
53.719
54.671
55.376
a Obtained from [16].
where X ¼ ðT ꢂ 384Þ=6. This equation applies to the
temperature range from T ¼ 378 K to T ¼ 390 K, with
an uncertainty of ꢀ0.20%.
except for several points around upper and lower limits
of the temperature range in the solid phase.
Figure 3 gives the plot of relative deviations of the
experimental heat capacity values, Cp;m(Expt), from the
fitted heat-capacity values, Cp;m(fit), against the absolute
temperature. It is seen from figure 3 that relative devi-
ations of most experimental points are within ꢀ0.50%
3.2. Melting point, molar enthalpy and entropy of fusion
Pre-melting occurred owing to the presence of im-
purities in the sample. The measurements of the melting
point and the molar entropy of fusion of the sample

Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
85
was evaluated. The enthalpy used to heat the empty
sample container and the sample itself (solid or liquid)
was subtracted from the total amount of heat intro-
duced to the sample and container during the whole
fusion, the melting enthalpy of the sample can be ob-
tained, as described in the literature [11].
Three series of heat-capacity experiments in the fu-
sion region of the compound were carried out so that the
reversibility and repeatability of the fusion region were
verified. Before each series of measurements, the sample
was cooled from T ¼ 390 K to T ¼ 300 K using different
cooling rates. In the first series, the sample was quen-
ched into liquid nitrogen (about 20 K ꢁ minꢂ1); in the
second series, the sample was naturally cooled (about
0.5 K ꢁ minꢂ1); and in the third series, the ice-water was
used as coolant (about 5 K ꢁ minꢂ1). The results of the
three series of repeated experiments are plotted in the
inset to figure 1 and also given in table 2. It can be seen
from figure 1 that the phase transition is reversible and
repeatable, no supercooling and other thermal anomaly
was caused by the different cooling rates.
FIGURE 2. The plot of experimental molar heat capacities (Cp;m=R) of
9-fluorenemethanol against the temperature (T) (‘‘ ’’, the first series
ꢃ
of heat capacity measurements; ‘‘n’’, the second series of heat capacity
measurements; ‘‘*’’, the third series of heat capacity measurements).
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
The melting temperature Tfus of the sample was cal-
culated from an equation based on the heat capacity in
the fusion region, as described in the literature [11]. The
molar enthalpy of fusion DfusHm was determined fol-
lowing the method described in the literature [11]. The
molar entropy of fusion, using DfusSm ¼ DfusHm=Tfus
,
was calculated.
The results of Tfus, DfusHm and DfusSm of the sample
obtained from the three series of repeated heat-capacity
measurements are listed in table 2.
-1.0
3.3. Constant-volume combustion energy, standard molar
enthalpy of combustion and standard molar enthalpy of
formation
75 100 125 150 175 200 225 250 275 300 325 350 375
FIGURE 3. The plot of relative deviations of the fitted heat-capacity
values ½Cp;mðfitÞꢅ from the experimental heat capacity values ½Cp;mðExptÞꢅ
against the absolute temperature. fDCp;m ¼ ½Cp;mðfitÞ ꢂ Cp;mðExptÞꢅg.
The method for determining the constant-volume
combustion energy of the sample was the same as that
used in the calibration of the calorimeter with benzoic
acid. The constant-volume combustion energy of the
sample can be calculated from the equation
were done as follows: the temperatures for the start of
the pre-melting and for complete melting were deter-
mined. Between these two temperatures the m.p. was
determined by successive approximation through step-
wise heating. Then, by heating the sample from a tem-
perature slightly lower than the initial melting
temperature to a temperature slightly higher than the
final melting temperature, the enthalpy of the sample
DcU=J ꢁ molꢂ1 ¼ ðecalor ꢁ DT ꢂ QNi ꢂ QHNO Þ ꢁ M=W
3
in which ecalor=J ꢁ Kꢂ1 was the energy equivalent of the
oxygen-bomb calorimeter; DT/K, the corrected temper-
ature rise; M/g ꢁ molꢂ1, the molar mass of the sample; W /
g, the mass of the sample.
TABLE 2
The results of melting of the compound obtained from three series of heat capacity measurements
Thermodynamic properties
fus/K
Series 1, x1
Series 2, x2
Series 3, x3
(x ꢀ ra)a
376.567 ꢀ 0.012
26.273 ꢀ 0.013
69.770 ꢀ 0.035
T
376.545
26.251
69.715
376.586
26.299
69.835
376.569
26.268
69.756
DfusHm/(kJ ꢁ molꢂ1
)
DfusSm/(J ꢁ Kꢂ1 ꢁ molꢂ1
)
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
3
2
a ra ¼
i¼1ðx1 ꢂ ꢀxÞ =nðn ꢂ 1Þ, in which n is the experimental number; xi, a single value in a set of dissolution measurements; x, the mean value of
a set of measurement results.

86
Y.-Y. Di et al. / J. Chem. Thermodynamics 36 (2004) 79–86
TABLE 3
The experimental results of the combustion energies of the compound obtained from the oxygen-bomb combustion calorimetry at T ¼ 298:15 K
No.
Sample
mass m/g
Heat value of
nickel wire QNi/J
Heat value of
nitric acid QN/J
Corrected temperature
rise DT/K
Combustion
energies ꢂDUc/(kJ ꢁ molꢂ1
)
1
2
3
4
5
6
0.9212
0.8922
0.9016
0.8882
0.9155
0.9088
39.5388
38.9530
39.2459
40.1246
38.0744
39.2459
49.4139
43.2372
47.3550
45.2961
48.6703
46.6423
2.4789
2.3981
2.4228
2.3878
2.4543
2.4429
7135.18
7127.73
7125.65
7128.33
7108.52
7127.93
Avg. DUc ¼ ꢂð7125:56 ꢀ 4:62Þ kJ ꢁ molꢂ1
The calculated results of the constant-volume com-
bustion energy of the sample were listed in table 3.
The standard molar enthalpy of combustion of the
sample, DcHmꢃ , was the combustion enthalpy change of
the following reaction at T ¼ 298:15 K and P0 ¼ 100
kPa based on the definition of the combustion enthalpy
about the organic compound
References
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Compounds, vol. IV, second ed., CRC Press, Boca Raton, FL,
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C14H12OðsÞ þ 33=2O2ðgÞ ¼ 14CO2ðgÞ þ 6H2OðlÞ:
The standard molar enthalpies of combustion can be
derived from the constant-volume combustion energy by
means of the following formula:
ð1Þ
[4] M.D.M.C. Ribeiro da Silva, M.A.V. Ribeiro da Silva, G. Pilcher,
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DcHmꢃ ¼ DcUm þ Dn ꢁ RT ;
X
X
Dn ¼
niðproducts; gÞ ꢂ
niðreactants; gÞ;
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P
where
products or reactants. The calculated standard molar
ni was the total molar amount of the gases in
enthalpy of combustion of the sample was: DcHmꢃ ¼
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ꢂð7131:76 ꢀ 4:62Þ kJ ꢁ molꢂ1
.
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Qu, Thermochim. Acta 359 (2000) 103–107.
The standard molar enthalpy of formation of the com-
pound, Df Hmꢃ , was calculated by a designed Hess thermo-
chemical cycle according to the reaction (1) as follows:
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67.
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Liu, J.-B. Zhang, J. Chem. Thermodyn. 34 (2002) 1417–
1429.
Df Hmꢃ ðC14H12O;sÞ ¼ ½14Df Hmꢃ ðCO2;gÞ þ 6Df Hmꢃ ðH2O;lÞꢅꢂ
DcHmꢃ ðC14H12O;sÞ:
In the above formula, the standard molar enthalpies
of formation of CO2(g) and H2O(l), recommended by
CODATA [17,18], Df Hmꢃ (CO2,g) ¼ ꢂ(393.51 ꢀ 0.13) kJ ꢁ
[12] D.A. Ditmars, S. Ishihara, S.S. Chang, G. Bernstein, E.D. West,
J. Res. Natl. Bur. Stand. 87 (1982) 159–163.
[13] M.W. Popov, Thermometry and Calorimetry (in Russian),
Moscow University Publishing House, Moscow, 1954,
p. 331.
molꢂ1 and Df Hmꢃ (H2O,l) ¼ ꢂ(285.83 ꢀ 0.04) kJ ꢁ molꢂ1
,
were employed in the calculation of Df Hmꢃ (C14H12O,s)
values. The standard molar enthalpy of formation of the
compound can be derived based on these values and
standard molar enthalpy of combustion of the substance
[14] X.-W. Yang, S.-P. Chen, S.-L. Gao, X.-H. Liu, Q.-Z. Shi, J. Rare
Earths 20 (2002) 167–171.
[15] F.D. Rossini (Ed.), Experimental Thermochemistry, vol. 1,
Interscience, New York, 1956, pp. 398–399.
to be: Df Hmꢃ (C14H12O,s) ¼ )(92.36 ꢀ 0.97) kJ ꢁ molꢂ1
.
[16] J.M. Peter, N.T. Barry, CODATA recommended values of the
fundamental physical constants: 1998, J. Phys. Chem. Ref. Data
28(6) (1999) 1713–1852.
Acknowledgements
[17] J.D. Cox, D.D. Wagman, V.A. Medvedev, CODATA Key
Values for Thermodynamics, Hemisphere, New York,
1989.
This work was financially supported by the National
Natural Science Foundation of China under the Grant
NSFC No. 20073047.
[18] J.D. Cox, J. Chem. Thermodyn. 10 (1978) 903–906.
JCT 03/078