Calorimetric thermograms

Fig. 12. Differential scanning calorimetric thermogram of cimetidine hydrochloride. 

Randzio, S. Suurkuusk, J. (1980). Interpretation of calorimetric thermograms and their dynamic corrections. In Biological Microcalorimetry (Beezer, A.E., ed.), pp. 311-341, Academic Press, London. 

An automatic sample charger was also designed and developed that enables a completely automated operation at very high temperatures. It allows a complete experimental run with successive addition of 30 samples. Each individual mixing experiment is computer operated and calorimetric thermograms are also automatically integrated. 

By changing the initial water vapor molar fraction in the reactor (varying the vapor pressure reserve temperature), an important variation of appears (r is the time of the maximum in the hydration isothermal calorimetric thermogram) ... 

Fig. 5. Calorimetric thermogram for the titration of 23 iM wt GSTPl-1 with 5 gL injections (1 qL first injection) of 2.1 mM EA in 20 mM sodium phosphate, 5 mM NaCl and 0.1 mM EDTA at pH 7.0 and 25°C. Inset plot Comparison between a peak from a calorimetric thermogram for the titration of wt enzyme with EA, reflecting the slow kinetic process caused by covalent modification (solid line) and a representative calorimetric trace of a typical binding peak in the absence of a kinetic process (dashed line).

Fig. 7. Protonation effect in the dUTP hydrolysis by PfdUTPase at pH 7 and 25 °C. The calorimetric thermograms correspond to one 20. iL injection of 9.98 mM dUTP to the calorimetric cell containing PfdUTPase (5.5 nM) in (solid line) glycerophosphate, (dash line) Pipes, (dash dot line) Mes, (dot line) Hepes and (dash dot dot line) TES. Upf>er, medium and bottom panels correspond to the calorimetric traces for dUTP dilution, protein titration and net (protein titration minus dUTP dilution), respectively. Right figure correspond to the fitting to Eq. 29 of the observed reaction enthalpy change, AHobs, obtained in each buffer system, versus the ionization enthalpy.

Fig. 24.3 Differential scanning calorimetric thermograms of poly ( 3 - (2 - (2 - methoxyethoxy) ethoxy) - 4 - methylthio-phene). (From Ref. 33.)...

As already indicated (Section IV.A), the quantity of heat evolved in the calorimeter cell is measured, in the case of usual heat evolutions, by the area limited by the thermogram. The integration of the calorimetric curves is, therefore, often needed. This may be achieved by means of integrating devices which may be added to the recorder. From our experience, however,... 

Let us consider a point M on a thermogram C, and the tangent MT to the calorimetric curve C, at this particular point. If the segment MH, parallel to the time axis, is equal to the first time constant n of the calo-... 

All heat evolutions which occur simultaneously, in a similar manner, in both twin calorimetric elements connected differentially, are evidently not recorded. This particularity of twin or differential systems is particularly useful to eliminate, at least partially, from the thermograms, secondary thermal phenomena which would otherwise complicate the analysis of the calorimetric data. The introduction of a dose of gas into a single adsorption cell, containing no adsorbent, appears, for instance, on the calorimetric record as a sharp peak because it is not possible to preheat the gas at the exact temperature of the calorimeter. However, when the dose of gas is introduced simultaneously in both adsorption cells, containing no adsorbent, the corresponding calorimetric curve is considerably reduced. Its area (0.5-3 mm2, at 200°C) is then much smaller than the area of most thermograms of adsorption ( 300 mm2), and no correction for the gas-temperature effect is usually needed (65). 

It must be acknowledged, however, that the determination of the number of the different surface species which are formed during an adsorption process is often more difficult by means of calorimetry than by spectroscopic techniques. This may be phrased differently by saying that the resolution of spectra is usually better than the resolution of thermograms. Progress in data correction and analysis should probably improve the calorimetric results in that respect. The complex interactions with surface cations, anions, and defects which occur when carbon monoxide contacts nickel oxide at room temperature are thus revealed by the modifications of the infrared spectrum of the sample (75) but not by the differential heats of the CO-adsorption (76). Any modification of the nickel-oxide surface which alters its defect structure produces, however, a change of its energy spectrum with respect to carbon monoxide that is more clearly shown by heat-flow calorimetry (77) than by IR spectroscopy. 

Heat-flow microcalorimetry may be used, therefore, not only to detect, by means of adsorption sequences, the different surface interactions between reactants which constitute, in favorable cases, the steps of probable reaction mechanisms, but also to determine the rates of these surface processes. The comparison of the adsorption or interaction rates, deduced from the thermograms recorded during an adsorption sequence, is particularly reliable, because the arrangement of the calorimetric cells remains unchanged during all the steps of the sequence. Moreover, it should be remembered that the curves on Fig. 28 represent the adsorption or interaction rates on a very small fraction of the catalyst surface which is, very probably, active during the catalytic reaction (Table VI). It is for these... 

Thermal Analyzer equipped with a differential calorimetric cell. TGA thermograms were obtained on a DuPont 1090 Thermal Analyzer. Elemental analyses were performed by Galbraith Laboratories, Knoxville, TN. 

Calorimetric Deconvolution Models and the Reversibility or Irreversibility of Overall Denaturation Processes. The deconvolution procedures used to analyze the thermograms presented in this study are based on equilibrium models, even though the overall denaturation process seen over a cycle of heating to a temperature above T and then cooling to below is, depending on the pH, either completely or partially irreversible. There is ample precedent in the literature for the application of equilibrium models in such cases, however. Convincing evidence has been presented... 

Determination of the reaction rate from calorimetric measurements, using DSC technique, is very useful and was applied with success for many template polymerization systems and for blank polymerizations.Two types of calorimetric measurements were described isothermal and scanning experiments. The heat of polymerization can be measured by DSC method, measuring thermal effect of polymerization and ignoring the heat produced from decomposition of the initiator and heat of termination. In isothermal experiments sample is placed at a chosen temperature and thermogram is recorded versus time. Assuming typical relationship... 

The calorimetric measurement per se can detect additional intermediates during transitions. There are clear-cut cases where two or more phases are seen in melting curves, or thermograms, showing that intermediates are appearing. The difficult case is when only one transition is seen. Whether or not there is a single transition can be tested by measuring A/fD N(cal) and A/fD H(vh) for the transition.13 (This does not require two separate experiments because the bell-shaped... 

Fig. 2. Thermogram of 10 M NaOH in H20. AT is the difference between the temperature of the calorimetric unit and that of the sample.

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