Authors:G. Baert, S. Hoste, G. De Schutter, and N. De Belie
Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the
acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days
increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)2-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic
reaction. A unique relation was found between calcium hydroxide and total heat development.
Isothermal calorimetry and UV-visible spectrophotometry have been used to study the thermochemistry of the enzyme-catalyzed
hydrolysis of hydrophobic L-amino acid esters in organic solvents with low water content at 298 K. The p-nitrophenyl esters of Z-L-tyrosine and Z-L-phenylalanine were used as model hydrophobic substrates. Acetonitrile was used as a model organic solvent. A special preparation
protocol of the reactants in the calorimetric vessel was applied in order to determine the heat effects accompanying the enzyme-catalyzed
hydrolysis reaction in organic mixtures with low water content and the Tris buffer ionization enthalpies over the whole range
of water content in acetonitrile.
It was found that the molar enthalpy of the hydrolysis of p-nitrophenyl esters and buffer ionization enthalpy depend significantly and similarly on the water content in acetonitrile.
However, the reaction enthalpy corrected for the buffer ionization enthalpy does not depend on the water content in organic
solvent mixtures. An explanation of the effect of the selected organic solvent on the thermochemical parameters was provided
on the basis of the IR spectroscopic data for the hydrogen bond network of water in acetonitrile. The results obtained show
that the state of water in organic solvents is an important factor that determines the reaction enthalpy as well as buffer
The conversion of either the gel or the liquid crystal phase to the most stable subgel phase in dimyristoylphosphatidylethanolamine
(DMPE)-water system at a water content of 25 mass% was studied by differential scanning calorimetry and isothermal calorimetry.
The calorimetric experiments were performed for two samples depending on whether the thermal treatment of cooling to -60C
was adopted or not. In DSC of varying heating rate, exothermic peaks due to the partial conversion were observed at either
temperatures just below the gel-to-liquid crystal phase transition at 50C or temperatures where the liquid crystal phase
is present as a metastable state. The enthalpies of conversion for both the gel and the liquid crystal phase were measured
directly by the isothermal calorimetries at 47 and 53C, respectively, where the exothermic peaks were observed by DSC and
were compared with the enthalpy difference between the gel and subgel phases and that between the liquid crystal and subgel
Authors:T. J. Snee, C. Barcons, H. Hernández, and J. M. Zaldívar
A simple esterification reaction is used to demonstrate standard procedures for determining the thermokinetic parameters of an exothermic reaction from adiabatic calorimetric data. The influence of variations in the heat capacity of the sample due to changes in temperature and concentration is explored. Shortcomings in the simple interpretation of adiabatic data are identified and isothermal heatflow calorimetry is used to reveal autocatalytic effects which were not apparent from the adiabatic experiments. A more rigourous interpretation of the adiabatic and isothermal data is outlined and used to predict the conditions which can lead to exothermic runaway in a batch reactor. Mathematical simulation of the conditions in a jacketed reactor is used to demonstrate the importance of developing reliable kinetic expressions before assessing the safety of a batch process.
A modified first-order kinetic law which takes into account defect decay during an ordering process was employed to predict the short-range-order kinetics of a quenched and a quenched-deformed Cu—5 at.% Zn alloy, in conjunction with experiments performed by isothermal calorimetry. The effective activation energy of point defect migration and its temperature dependence strongly suggest the contribution of bound vacancies to the ordering process. An estimate of 91.2 kJ mol–1 was made for the activation energy of solute—vacancy migration by applying an effective rate constant, a value in very good agreement with that obtained from previous non-isothermal experiments. The isothermal curves were utilized to determine the ordering energy: w=–2.90 kJ mol–1. In conjunction, a parametric study of the defect sink density was performed in order to assess its influence on the calculated isothermal curve profiles.
Authors:Magdalena Troć, A. Skoczowski, and Małgorzata Barańska
The extracts from sunflower and mustard leaves were separated using SPE-Columns. The mustard seeds were germinated on water
(24 h) and subsequently on crude extracts or separate fractions. The heat production rate was measured by isothermal calorimetry
at 21°C and changes in seed cotyledons by FT-Raman spectroscopy. Crude extracts strongly inhibited seed germination. The water
and ‘methanol’ fractions of mustard and sunflower extracts have a similar influence on the pattern of heat efflux. FT-Raman
spectroscopy showed that extracts caused changes in cotyledons mainly in the content of fatty acids, carotenoids and flavonoids.
Isothermal calorimetry and Raman spectroscopy are useful for the study of allelopathic interactions.
Authors:B Finnin, M O'Neill, S Gaisford, A Beezer, J Hadgraft, and P Sears
calorimetry is becoming indispensable as a tool for the study of a wide variety
of systems. As with all scientific instruments it is essential that robust
calibration routines be developed in order to validate the data obtained.
Chemical test reactions offer many advantages over (the traditionally used)
joule effect heating methods, not least because they have the potential to
validate instrument performance (i.e. they can be used to assess all aspects
of calorimeter operation). In this work the results of a validation exercise,
conducted by Thermal Hazard Technology as part of an installation routine,
using the base catalysed hydrolysis of methyl paraben are discussed. In the
case described, a systematic misreporting of the reported temperature of a
calorimeter was identified, caused by an upgrade to the calorimeter's
firmware, a discrepancy which may not have been noted using traditional electrical
calibration methods and one which highlights the importance of both manufacturers
and end-users adopting chemical test reactions into their test and validation
Authors:M. O’Neill, S. Gaisford, A. Beezer, C. Skaria, and P. Sears
calorimetry is finding extensive application in a number of research areas.
This popularity is reflected in the number of commercially available instruments
which are capable of yielding a variety of thermodynamic and kinetic parameters.
Whilst there has been much discussion of ways in which to validate any values
returned from these instruments very little has been done quantitatively to
compare the relative performances of different instruments. This paper highlights
the use of a test and reference reaction quantitatively to compare the performance
of three instruments (Thermometric TAM, THT RC and a Setaram HSDSC
III); the specifications of these instruments provide a range from high-sensitivity,
long equilibration time to lower-sensitivity, short equilibration time. The
comparison is made through a statistical analysis of values returned for the
rate constant, enthalpy of reaction and activation energy for the base catalysed
hydrolysis of methyl paraben. The statistical analysis from the data set discussed
here indicates that there is no significant difference between the returned
thermodynamic and kinetic parameters from the TAM and RC. The analysis
revealed however that the HSDSC returns values for the rate constant which
are significantly different from both the TAM and RC, although it is
noted that this instrument was not specifically designed to operate in a step-isothermal
mode and that it was possible to apply a correction to the data. In all cases
the enthalpy data returned from all instruments were statistically similar
although the RC and HSDSC returned values which were, for the rate
constant and activation energy, less precise than those obtained from the
TAM. As well as highlighting the importance of using test and reference reactions,
this study also shows that proper instrument selection is an important factor
when designing a calorimetric experimental series.
An isothermal method was applied to measure the thermal
decomposition of reactive solids in a sensitive heat flux reaction calorimeter,
C80. This technique experimentally clarified the decomposition mechanisms
of unstable substances based on the shapes of the heat flow curves, from which
autocatalysis, first-order reaction or pseudo-autocatalytic reaction could
be recognized. Kinetic parameters were derived from the measured data.