Temperature programmed decomposition of cobalt ethylene diamine complexes

Article abstract of DOI:10.1016/S0040-6031(99)00186-0

The cobalt co-ordination complexes, [Co(en)₂Cl₂]Cl and [Co(en)₂CO₃]Cl, synthesised through literature procedures, were characterised by FTIR. Trace metallic impurities were determined by ICP-MS. Crystallinity of the samples were ascertained by preliminary X-ray powder diffraction analysis. Dark field polarised optical microscopy (OM) was used to observe particle size distribution. These compounds were subjected to temperature programmed decomposition (TPD) in thermogravimetric analyser (TGA). TPD was also carried out in a home built mass spectrometry based evolved gas analyser (EGA-MS). The complex TGA weight loss profile could be successfully explained through EGA data. Complimentary information received from both the above techniques indicated sequential decomposition, prevalence of steric effect and functional group ejection. The non-isothermal kinetic analysis of TGA and EGA data showed dominance of kinetic control mechanisms based on sigmoidal rate laws like Avarami-Erofeev (AE) and random nucleation (RN). The fraction release α ~ T plots were used to evaluate integral model function g(α) of non-isothermal kinetic rate expressions. From log[g(α)/T²] ~ 1/T plots of well correlated model functions, Arrhenius parameters like activation energy and pre-exponential factors were evaluated for various decomposition steps.

Full text of DOI:10.1016/S0040-6031(99)00186-0

Thermochimica Acta 334 (1999) 141±148
Temperature programmed decomposition of cobalt ethylene
diamine complexes
S. Dash*, P.K. Ajikumar, M. Kamruddin, A.K. Tyagi
Materials Science Division, Indira Gandhi Centre for Atomic Research, 603 102 Kalpakkam, India
Received 14 May 1998; accepted 10 June 1999
Abstract
The cobalt co-ordination complexes, [Co(en)2Cl2]Cl and [Co(en)2CO3]Cl, synthesised through literature procedures, were
characterised by FTIR. Trace metallic impurities were determined by ICP-MS. Crystallinity of the samples were ascertained
by preliminary X-ray powder diffraction analysis. Dark ®eld polarised optical microscopy (OM) was used to observe particle
size distribution. These compounds were subjected to temperature programmed decomposition (TPD) in thermogravimetric
analyser (TGA). TPD was also carried out in a home built mass spectrometry based evolved gas analyser (EGA-MS). The
complex TGA weight loss pro®le could be successfully explained through EGA data. Complimentary information received
from both the above techniques indicated sequential decomposition, prevalence of steric effect and functional group ejection.
The non-isothermal kinetic analysis of TGA and EGA data showed dominance of kinetic control mechanisms based on
sigmoidal rate laws like Avarami±Erofeev (AE) and random nucleation (RN). The fraction release ꢀ ꢀ T plots were used to
evaluate integral model function g(ꢀ) of non-isothermal kinetic rate expressions. From log[g(ꢀ)/T2] ꢀ 1/T plots of well
correlated model functions, Arrhenius parameters like activation energy and pre-exponential factors were evaluated for
various decomposition steps. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Co-ordination complex; Sequential decomposition; Steric effects; Activation energy
1. Introduction
gas studies angle. In this context, it is noteworthy that
a large number of cobalt ethylene diamine complexes
were investigated by Wendlandt et al. [3] using ther-
mal analysis. However, complex weight loss beha-
viour during thermal decomposition, probably
accruing from multistep sequential reactions was
not explained [4]. In thermogravimetric analysis
(TGA) and DTA investigation of [Co(en)2X2]X type
of halogen bearing compounds, Zsako et al. [5] had
suggested that the complex weight loss behaviour is
attributable to superposition of several intermediate
reactions. In his paper, Ingier-stocka [6] had recom-
mended dynamic thermal analysis as the best proce-
Cobalt(III) ethylene diamine complexes constitute
an important class of inorganic co-ordination com-
pounds due to their fundamental as well as practical
signi®cance. Initial interest in [Co(en)2Cl2]Cl accrued
from optical isomerism [1]. Also this compound
occurs as an important mechanistic intermediate in
many inorganic preparations [2]. [Co(en)2CO3]Cl, a
substituted derivative of the above compound is quite
interesting from thermal decomposition and evolved
*Corresponding author.
0040-6031/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 0 4 0 - 6 0 3 1 ( 9 9 ) 0 0 1 8 6 - 0

142
S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
Table 1
dure for comparison of thermal stability of homolog-
ous series of co-ordination complexes. In the light of
the above, we have tried to explain the complex weight
loss pro®les of [Co(en)2Cl2]Cl and [Co(en)2CO3]Cl
obtained from dynamic TGA runs through gaseous
species data acquired from off-line dynamic EGA
runs. Based on TGA and EGA-MS data, we have
carried out comparison of thermal stabilities of these
complexes. These data have also been used to derive
the kinetics of various decomposition stages and
obtain arrhenius parameters like activation energy
and pre-exponential factor.
Trace metallic impurity analysis by ICP-MS
Sl. no. Trace elements Concentration (mg/g)
[Co(en)2Cl2]Cl
[Co(en)2CO3]Cl
1
2
Al
Ba
Cu
Cr
Fe
Mn
Mo
Ni
Pb
Sr
23
<5
28
<2
62
54
<2
10
<5
<5
4
3
4
5
52
17
<2
6
7
8
198
120
9
140
<5
<2
94
26
<5
<2
29
10
11
12
Ti
Zn
2. Preparation and characterisation
The cobalt ethylene diamine complexes were
synthesised by wet chemical routes according to
procedures outlined in literature [7]. The trans-
dichloro-bis-ethylene diamine Co(III) chloride (here-
after known as compound I) was prepared by crystal-
lisation from aqueous solution of CoCl2Á6H2O and
ethylene diamine. The compound II (carbonato-bis-
ethylene diamine Co(III) chloride) was substitution-
ally derived from compound I by reaction with
Na2CO3. The ®nely divided powder sample was
observed by polarised optical microscopy in the dark
®eld re¯ection mode [8]. The particles showed a size
distribution over a narrow regime in the 15 Æ 5 micron
span [9]. Trace metallic constituents in these com-
pounds were determined using an ELAN 250 Induc-
tively coupled plasma mass spectrometer (ICP-MS)
supplied by SCIEX, Canada [10]. The samples were
dissolved in spectroscopically pure reagents and
sprayed to ICP by use of a peristaltic pump and
meinhard nebuliser [11]. Data were acquired by rapid
scan mode. The instrument was calibrated using syn-
thetic spectroscopically pure NBS traceable standards.
Concentration of metallic impurities was found to be
in micro-gm/gm level. These are presented in Table 1.
The powder samples were blended with spectroscopic
grade KBr powder and palletised. These pellets were
subjected to FTIR analysis in the transmission mode.
Vibrational assignments to FTIR spectra of these
numbers. Prominent infrared absorption bands for
trans [Co(en)2Cl2]Cl was assigned as following: for
NH2 the asymmetric deformation occurred at
1
1593 cm 1, symmetric deformation at 1366 cm
,
rocking mode at 806 cm 1; for CH2 the stretching
mode was found at 2939 cm 1, bending mode at
1464 cm 1, wagging mode at 1272 cm 1 and twisting
mode at 1115 cm 1 [13]. Unsplitting NH2 asymmetric
1
deformation frequency at 1593 cm indicated trans
character of the compound [14]. A similar observation
has been reported for the isostructural compound
[Ir(en)2Cl2]Cl [15]. For its derivative compound, i.e.
carbonato complex [Co(en)2CO3]Cl, following funda-
mental spectral absorption characteristics matches
were noted [16]. CO2 bending is observed at
1
758 cm 1, CO2 symmetric stretch at 1270 cm
,
CO stretch at 1056 cm 1, non-planar rocking at
1
832 cm and asymmetric stretching at 1580 cm
1
.
Barring external ion effect, the broad matching of data
with spectral analysis of carbonato complex reveals
prevalence of bidentate covalent nature of bonding
[17]. Strong infrared absorption bands exhibited by
ethylene diamene functional group [18,19] obscured
the spectral characteristics of co-ordination com-
pounds. These compounds were subjected to X-ray
diffraction analysis in a Stoe powder diffraction sys-
tem. The powders were found to be crystalline.
[Co(en)2Cl2]Cl showed a monoclinic crystal structure
[20], whereas preliminary space group analysis sug-
gested [Co(en)2CO3]Cl to be triclinic.
compounds acquired from a Perkin-Elmer spectro-
1
meter operating in the range 400±4500 cm
was
carried out with the help of published literature
[12]. Spectral matches were found within 2±3 wave

S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
143
3. Experimental
4. Results and discussion
TGA runs of these compounds were conducted in a
Setram 92 TG, DTA apparatus using inert argon as
¯owing carrier gas at a heating rate of 10 K/m. Off-
line mass spectrometry based evolved gas analysis
(EGA-MS) studies were conducted under high
vacuum conditions in our home built EGA-MS appa-
ratus. Description of this facility is published else-
where [21±23]. Essentially this facility is a high
vacuum, high temperature resistance furnace coupled
to an ultra high vacuum chamber housing a quadruple
mass spectrometer through a leak valve. A computer
assisted multiple ion detection, multichannel trend
analysis mass spectrometry (MID-MS) software plots
MID signals of evolved gases released from solids
undergoing decomposition against specimen tempera-
ture to give EGA-MS plots.
Compound I: Fig. 1 a shows the TGA plot of TPD
of [Co(en)2Cl2]Cl. This complex pro®le is a convolu-
tion of several weight loss stages. Earlier works
[24,25] have observed this behaviour for certain other
amine based chloro compounds. In our studies the
initial ꢀ5% weight loss at 475 K was attributed to
adsorbed moisture. This is substantiated by initial
water release signal in EGA spectra, described below.
Since our analysis was con®ned to thermal decom-
position, this stage was not considered. Deconvolution
of the TG pro®le showed four weight loss stages.
These stages are marked in Fig. 1a as I, II, III and
IV. The weight losses for these stages are 6.2%,
26.3%, 12.6% and 7.1% with temperature spans of
525±575, 570±725, 650±775 and 760±885 K respec-
tively. The residue at 730 K corresponds to CoCl3. The
®nal weight loss is continuous. The above weight
losses could be explained with the help of off-line
EGA-MS studies. However, minor discrepancies
Fig. 1. (a) TGA plot with deconvoluted stages of TPD of
[Co(en)2Cl2]Cl; (b) the corresponding fraction release plot.
Fig. 2. (a) EGA-MS spectra of [Co(en)2Cl2]Cl; (b) the correspond-
ing fraction release plot.

144
S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
between these two studies are attributable to different
sample environments.
CoCl3 ! CoCl2. This is seen from detection of 35Cl in
EGA-MS beyond temperature 730 K.
The EGA-MS spectra of compound I is shown in
Fig. 2a. The species corresponding to masses were:
m/e ˆ 16, CH4; m/e ˆ 17, NH3; m/e ˆ 30 and 43,
ethylene diamine (en) fragments; m/e ˆ 35, volati-
lised chlorine signals were detected. The decomposi-
tion occurs with concomitant release of CH4 and NH3.
The CH4 and NH3 release is accompanied with en
ejection. Formation of CH4 and NH3 can be attributed
to bond cleavage effects. Also en fragmentation does
not contribute to masses 16 and 17 [26]. As we have
observed CH4 and NH3 species also, it suggests that
out of the two en ligands one undergoes dissociation.
The reason can be attributed to crystallographic
inequivalence of en ligands in monoclinic unit cell
of [Co(en)2Cl2]Cl [27]. Based on these observations
the weight loss steps can be ascribed to, stage I: NH3
release; stage II: CH4 and en ejection; stage III: release
of remaining NH3 and CH4; stage IV: conversion of
In case of TPD of [Co(en)2Cl2]Cl, the EGA-MS
spectra could successfully explain the TGA weight
loss curve barring minor discrepancies. The discre-
pancies stem from different operating environments
seen by the sample in TGA and EGA runs. In TGA
runs NH3 and CH4 release occur in two stages and en
ejection in single step. But in EGA-MS, the release of
NH3 and CH4 occur in three overlapped stages and en
in two stages. The temperature regimes were slightly
lower. The reason for better resolution can be attrib-
uted to prevailing vacuum condition, which ensures
near total irreversibility. The sequential multistep
decomposition is in conformity with observation made
in certain other Co(III) ethylene diamine based com-
plexes. In these cases the internal co-ordination sphere
ligands are sequentially replaced by external sphere
anions [28]. Similar functional group ejection in other
cobalt amine complexes had been reported by Zsako
et al. [2]. They have also suggested substitution of
internal sphere functional groups by external sphere
anions as possible mechanisms.
Fig. 3. (a) TGA plot with deconvoluted stages of TPD of
[Co(en)2CO3]Cl; (b) the corresponding fraction release plot.
Fig. 4. (a) EGA-MS spectra of [Co(en)2CO3]Cl; (b) the corre-
sponding fraction release plot.

S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
145
Compound II: Deconvoluted TGA curve of TPD of
[Co(en)2CO3]Cl shows four weight loss stages
(Fig. 3a). These weight losses are 27.2%, 10.3%,
18.6% and 4.3% at temperature spans of 525±565,
550±600, 600±700 and 700 K and above. Compared to
compound I, various reaction initiation and comple-
tion temperatures in this compound are rather low.
This can be attributed to steric instability arising from
location of large carbonato oxyanion in the internal
co-ordination sphere. Such steric instability has been
reported for other amine based cobalt co-ordination
compounds [29]. This instability is also responsible
for various decomposition stages of compound II
exhibiting smaller temperature spans than compound
I. This compound yields CoCl2 as ®nal product at
730 K.
dissociation of one of the two en ligands. From the
release pro®les and temperature spans stage I weight
loss can be attributed to release of CH4‡NH3‡CO2 ,
stage II is accounted by release of NH3 and CH4, en
ejection explains stage III weight loss. Stage IV
weight loss is due to continuous volatilisation of
end product CoCl2. Obviously the 35Cl signature
observed in the EGA-MS spectra of compound I is
absent in this case. Volatilisation of reaction product
CoCl2 has also been reported by Wendlandt et al. [30]
in their investigation of similar chloro amine com-
pounds. The TGA weight loss stage match very well
with EGA-MS data. The CO2 release is single step and
is concomitant with CH4 and NH3 release. CH4 and
NH3 release extend beyond CO2 and account for stage
II weight loss. The TG data shows loss of en as stage
III but in EGA en emission appears between two
CH4 ‡ NH3 release stages. This can be attributed to
superior resolution of EGA over TGA especially
where narrow temperature spans covering various
reaction stages are encountered. Also the operating
Here again, the weight losses are explainable on the
basis of off-line EGA-MS runs. The EGA-MS spectra
for this compound is given in Fig. 4. As seen from this
®gure, the gaseous products of decomposition are
constituted by CH4, NH3, CO2 and en indicating
Table 2
Non-isothermal, integral forms of kinetic expression for heterogeneous solid-state reactions
R
Reaction mechanism
Symbol f(ꢀ)
gꢁꢀ† ˆ 1 dꢁꢀ†=fꢁꢀ†
0
Nucleation and growth models
Random nucleation approach
(i) Mampel unimolecular law
A1
A (1/n) 1/n(1 ꢀ)[ ln(1 ꢀ)]1
B1 ꢀ(1 ꢀ)
1
ꢀ
ln(1 ꢀ)
ln(1 ꢀ)]n n ˆ 1/4, 1/3, 1/2, 2/3
n
(ii) Avrami±Erofeev nuclei growth
(iii) Branching nuclei: (Prout±Tompkins)
[
ln[ꢀ/(1 ꢀ)]
Accelerating rate equations
(i) Power law
n
)
P (1/n) 1/(nꢀ1
ꢀn n ˆ 1/4, 1/3, 1/2, 1, 3/2, 2
ln ꢀn; n ˆ 1,2
(ii) Exponential law
En
1/nꢀ
Decelerating rate equations
(a) Based on diffusion mechanism
(i) 1-dimensional diffusion
(ii) 2-dimensional diffusion
1
D1
D2
D3
ꢀ
[
ꢀ2/2
1
ln(1 ꢀ)]
(1 ꢀ)[ln(1 ꢀ)] ‡ ꢀ
1/3
1
(iii) 3-dimensional diffusion (Jander)
(1 ꢀ) 1/3[1 (1 ꢀ)
]
3/2[1 (1 ꢀ)1/3 2
]
1
(iv) 3-dimensional diffusion (Ginstling±Brounshtein) D4
[(1 ‡ ꢀ)1/3 1]
3/2[1 2ꢀ/3 (1 ꢀ)2/3
3/2[(1 ‡ ꢀ)1/3 1]2
]
1/3
]
1
(v) 3-dimensional counter diffusion (Anti±Jander)
D5
(1 ‡ ꢀ)1/3[1 (1 ‡ ꢀ)
(b) Based on phase boundary movement
(i) 1-dimensional (Zero order)
R1
R2
R3
Constant
(1 ꢀ)1/2
(1 ꢀ)2/3
ꢀ
(ii) 2-dimensional (cylindrical symmetry)
(iii) 3-dimensional (spherical symmetry)
2[1 (1 ꢀ)1/2
3[1 (1 ꢀ)1/3
]
]
(c) Based on order of reaction
(i) Reaction order
n
Fn
1/2(1 ꢀ)1
1
(1 ꢀ)n; n ˆ 2,3,4

146
S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
environment at lower heating rate aids better resolu-
tion.
values. Table 2 gives the non-isothermal kinetic rate
expressions used by us [31,32]. The expression show-
ing the best-correlated plot was considered to be the
prevailing mechanism. From the slopes of ln[g(ꢀ)/
T2]ꢀ1/T plots, activation energies were deduced. The
intercept of the plots yielded pre-exponential factor.
Table 3 gives the details of prevailing mechanism,
correlation coef®cient, activation energy and pre-
exponential factor for various weight loss and gas
release stages.
5. Kinetic analysis
Fraction release ꢀ(T) ꢀ T curve were computed for
TGA as well as EGA runs. These curves are shown in
Fig. 1b and Fig. 3b for TGA runs and Fig. 2b and
Fig. 4b for EGA runs. The integral model function
g(ꢀ) for non-isothermal kinetic rate expressions
were obtained and least square ®tted to experimental
The kinetic analysis of TGA and EGA results for
various decomposition stages of these compounds
Table 3
Reaction mechanism, correlation coefficient, activation energy and pre-exponential factors obtained for various decomposition stages studied
by TGA and EGA-MS techniques
Sample
Technique
m/z or
Stage
ꢀ range
Reaction
EA
Pre-exp.
1
factor (m )
Correlation
coefficient
species
mechanism
(KJ/mol)
[Co(en)2Cl2]Cl
TGA
I
0.18±78
0.2±78
AE(n ˆ 3/2) 160.436
8.8Â1014
3.5Â108
1.6Â108
1.5Â1012
0.99673
0.99788
0.99738
0.99908
II
RN
RN
RN
110.822
119.335
206.219
III
IV
0.18±81
0.22±83
EGA-MS
16
17
en
I
0.17±81
0.2±8
AE(n ˆ 3/2) 306.281
AE(n ˆ 3/2) 240.453
1.8Â1031
9.7Â1020
2.1Â1017
0.99569
0.99746
0.98871
II
III
0.2±84
RN
220.271
I
0.21±8
0.17±81
0.2±8
AE(n ˆ 3/2) 294.913
1.2Â1030
1.9Â106
1.9Â1018
0.99698
0.99736
0.98929
II
III
RN
RN
80.782
231.603
I
0.2±8
0.21±78
RN
122.409
3.8Â1010
1.3Â1019
0.99971
0.98362
II
AE(n ˆ 3/2) 238.318
[Co(en)2CO3]Cl TGA
I
0.2±8
AE(n ˆ 3/2) 188.648
AE(n ˆ 3/2) 208.14
9.2Â1017
5.5Â1018
1.1Â106
4.9Â107
0.99704
0.99712
0.99848
0.99804
II
0.2±8
III
IV
0.21±78
0.2±79
RN
RN
84.287
135.74
EGA-MS
16
17
I
0.17±82
0.18±82
RN
RN
202.916
77.126
9.8Â1019
8.8Â105
0.99642
0.99749
II
I
0.16±8
RN
RN
186.992
80.782
1.9Â1019
1.9Â106
0.99674
0.99736
II
0.16±81
en
I
I
0.2±8
AE(n ˆ 3/2) 180.862
RN 231.394
3.6Â1017
7.7Â1022
0.99418
0.99937
CO2
0.21±81

S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
147
reveal preponderance of sigmoidal character. Initial
stages con®rm to kinetic control by Avarami±Erofeev
(AE) rate expressions having dimensionality 3/2. This
dimensionality indicates complex but geometrically
isotropic growth of product nuclei [33]. Such rapid
nucleation process is indicative of many other solid
state decomposition reactions where physical pro-
cesses like structural phase transformations and
recrystallation are encountered.
FTIR studies on transition metal ethylene diamene
complexes have indicated evidence of strong hydro-
gen bonding [34] These hydrogen bonded structures
are likely to undergo amorphosization due to hydro-
gen bond loss. Such solid state structural collapse
leads to generation of nascent nucleation sites for
predominantly surface desorption controlled random
nucleation (RN) mechanism to proceed. This mechan-
ism is expressed through Mampel unimolecular
rate law. The intermediate kinetics observed by us
indicates governance by RN approach. Such obser-
vations regarding prevalence of RN mechanism suc-
ceeding structural collapse have been observed by us
in the TPD study of other H-bonded solids like
Al-alum [35].
tion in condensed phase concomitant with observed
gas release/decomposition stages.
Acknowledgements
The authors are grateful to Dr. Baldev Raj and Dr.
T.S. Radhakrishnan for their constant and continued
support. We also acknowledge the instrumentation
support rendered by Dr. B. Purnaih and Shri J. Jaya-
pandian. We are grateful to Dr. T.R. Mahalingam and
Shri R. Krishna Prabhu for ICP-MS runs, Shri K.
Varatharajan for optical microscopy and Dr. K.S.
Viswanathan for useful discussion on FTIR data.
References
[1] R.D. Archer, in: S. Kirschner (Ed.), Co-ordination Chemistry,
Plenum Press, New York, 1969.
[2] J. Zsako, M. Varhelyi, C.S. Varhelyi, J. Thermal Anal. 17
(1979) 123.
[3] W.W. Wendlandt, J.P. Smith, The Thermal Properties of
Transition Metal Ammine Complexes, Elsevier, Amsterdam,
1967.
[4] W.W. Wendlandt, T.D. George, K.V. Krishnamurty, J. Inorg.
Nucl. Chem. 21 (1961) 69.
[5] J. Zsako, M. Varhelyi, C.S. Varhelyi, Gy. Liptay, Thermo-
chim. Acta 51 (1981) 277.
6. Conclusion
[6] E. Ingier-stocka, Thermochim. Acta 170 (1990) 107.
[7] J.B. Bailar, Inorganic Syntheses, McGraw-Hill, New York,
vol. 2, 1946, p. 221.
Cobalt ethylene diamene complexes, synthesised
through literature procedures, were characterised by
OM, FTIR and ICP-MS. Complimentary real time
TGA and EGA-MS runs on TPD of the chloro-com-
plex and its subtitutional carbonato derivative revealed
sequential multistep decomposition. Owing to steric
instability, the carbonato derivative had lower reaction
initiation temperature as well as narrow temperature
span for various decomposition stages. Important
observations made by us like functional group ejec-
tion, CoCl2 formation and end product volatilisation
are consistent with reported literature giving TGA
results on similar chloro amine complexes. The gov-
ernance of sigmoidal rate laws like AE and RN
expressions indicate persistence of active surfaces
owing continued generation to bond disruptive effects.
However, in this study, structural correlations addres-
sing these effects have not been done. Hence, we plan
to undertake high temperature real time X-ray diffrac-
tion measurements to map out structural transforma-
[8] H.E. Knechtel, W.F. Kindle, J.L. McCall, R.D. Buchheit, in:
T. Lyman (Ed.), Metals Handbook, vol. 8, American Society
for Metals, OH, 1973, p. 10.
[9] D.A. Elkington, R. Wilson, in: P.J. Lloyd (Ed.), Particle Size
Analysis, Wiley, New York, 1987, p. 261.
[10] T.R. Mahalingam, in: S.K. Aggarwal, H.C. Jain (Ed.),
Introduction to Mass Spectrometry, Indian Society for Mass
Spectrometry, 1997, p. 13.
[11] S. Vijaylakshmi, R. Krishna Prabhu, T.R. Mahalingam, C.K.
Mathews, At. Spectrosc. 13(2) (1992) 61.
[12] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Co-ordination Compounds, Wiley, New York, 1963, p. 208.
[13] M.L. Morris, D.H. Busch, J. Am. Chem. Soc. 82(7) (1960)
1521.
[14] T.A. McLean Jr., A.F. Schneifner, A.F. Laethem, J. Inorg.
Nucl. Chem. 26 (1964) 1245.
[15] S. Kida, Bull. Chem. Soc. Japan 39 (1966) 2415.
[16] B.M. Gatehouse, S.E. Livingstone, R.S. Nyholn, J. Chem.
Soc. part III, art. 636, 1958, p. 3137.
[17] J. Fujita, A.E. Martell, K. Nakamoto, J. Chem. Phys. 36(2)
(1962) 339.
[18] D.B. Powel, Spectrochim. Acta 16 (1960) 241.

148
S. Dash et al. / Thermochimica Acta 334 (1999) 141±148
[19] B. Schrader, in: W. Meir (Ed.), DMS Raman/IR Atlas of
Organic Compounds, vol. 1, Verlag Chemie, Weinheim, 1978,
pp. A7±O7.
[27] R.W.G. Wyckoff, Crystal Structures, vol. 5, 2nd ed.,
InterScience Publishers, New York, 1996, p. 355.
[28] G. Grassini-Strazza, A. Cristalli, V. Carunchio, A. Messina,
Thermochim. Acta 36 (1980) 161.
[20] J.M. Williams, Inorg. Nucl. Chem. Lett. 3 (1967) 297.
[21] M. Kamruddin, P.K. Ajikumar, S. Dash, B. Purniah, A.K.
Tyagi, K. Krishan, Instr. Sci. Technol. 23(2) (1995) 123.
[22] M. Kamruddin, P.K. Ajikumar, S. Dash, R. Krishnan, A.K.
Tyagi, K. Krishan, J. Thermal Anal. 48 (1997) 277.
[23] S. Dash, M. Kamruddin, A.K. Tyagi, Bull. Mater. Sci. 20(3)
(1997) 359.
[29] R. Bucci, A.D. Magri, A.C. Magri, A. Messina, Thermochim.
Acta 60 (1983) 287.
[30] W.W. Wendlandt, E.L. Simons, Thermochim. Acta 36 (1980)
239.
[31] A.B. Phadnis, V.V. Deshpande, Thermochim. Acta 62 (1983)
361.
[24] J. Zsako, J. Horak, C.S. Varhelyi, J. Thermal Anal. 20 (1981)
435.
[32] M.E. Brown, Introduction to Thermal Analysis, Chapman and
Hall, London, 1988, p. 131.
[25] R. Wojciechowska, P. Bragiel, M. Czerwinki, J. Thermal
Anal. 36 (1990) 1295.
[33] A.K. Galway, Chemistry of Solids, Science Paperbacks,
Chapman and Hall, London, 1967, p. 173.
[26] A. Cornu, R. Massot, Compilation of Mass Spectral Data,
Part A, Commisariat A L' Energie Atomique, vol. 1, Heyden
and sons, London, 1975, p. 5A.
[34] D.B. Powel, N. Sheppard, Spectrochim. Acta 17 (1961) 68.
[35] M. Kamruddin, P.K. Ajikumar, S. Dash, R. Krishnan, A.K.
Tyagi, K. Krishan, Thermochim. Acta 287 (1996) 13.