Calorimetry isoperibolic

Constant jacket temperature measuring techniques, known as isoperibolic calorimetry, are designed to investigate the thermal behavior of substances and reaction mixtures under processing conditions [89,102-108]. 

Isoperibolic equipment consists of a sample container that is placed in a circulating air oven or heater. Typically, the sample container, of which there are several types, consists of a small tube or beaker that can contain a 5 to 30 g sample. The temperature range of commercial instruments is about 0 to 300°C. Some instruments include small autoclaves or small stirred vessels. Open vessels are made of glass while autoclaves are constructed of stainless 

In an isoperibolic experiment, the jacket temperature of the sample container (or the surroundings of the container, i.e., the oven temperature) is held constant. On attaining a steady-state, a temperature difference between the sample and jacket may be obtained, which becomes (1) zero (within the detection limit of the equipment) if no energy is released from the sample, or (2) positive if energy is released due to chemical reaction or decomposition. If no temperature difference is recorded after a fixed time interval, the oven temperature is increased (typically 5°C) and held constant once again. This procedure is repeated until an exothermic event is observed. 

Commercially available instruments include the SEsitive Detector of Exothermic processes (SEDEX) [103,104], SIKAREX [106], with a typical sensitivity of 0.5 W/kg), and RADEX [102, 108]. This equipment can also be run inisothermal and scanning modes. 

The onset temperature of exothermic activity, data on the autocatalytic decomposition, and the induction time for exothermic decomposition can be obtained. Also, it is possible to get pressure-time data with the correct instrument. 

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This paper considers systems of lesser dimensionality than the previous study, namely, systems of two compounds, which (ignoring the vapor) can form only one or two phases. Specifically, excess enthalpies and phase compositions have been measured (at ambient pressure) by isoperibol calorimetry for n-butanol/water at 30.0 and 55.0 °C and for n-butoxyethanol/water at 55.0 and 65.0 °C. (Butanol, or C4E0, is C HgOH butoxyethanol, or C4E1, is C HgCX OH.) The miscibility... 

Isoperibolic calorimetry measurements on the n-butanol/water and n-butoxyethanol/water systems have demonstrated the accuracy and convenience of this technique for measuring consolute phase compositions in amphiphile/water systems. Additional advantages of calorimetry over conventional phase diagram methods are that (1) calorimetry yields other useful thermodynamic parameters, such as excess enthalpies (2) calorimetry can be used for dark and opaque samples and (3) calorimetry does not depend on the bulk separation of conjugate fluids. Together, the present study and studies in the literature encompass all of the classes of compounds of the amphiphile/CO ydrocarbon/water systems that are encountered in... 

Because of the medium or relatively large sample quantities used and the instrumental sensitivity, isoperibolic calorimetry is a useful tool in determining the onset temperature of an exotherm. In fact, in its simplest construction, this is really the only measurement. Digital data acquisition does allow computer analysis of the peak or area under the curve, which indicates the order of magnitude of the exotherm. Generally, the detected onset temperatures are similar to those found in the ARC (see later in Section 2.3.23) and are significantly lower than in the DSC (Section 2.3.1.1) [79]. 

The equipment is quite adequate for screening purposes. In its simplest form (i.e., a glass tube in an oven), it is a relatively low cost technique that can be assembled with standard laboratory equipment. However, the simple test set-up provides no quantitative thermal data for scale-up purposes, but only T0 values. The more advanced instruments like the SEDEX and SIKAREX, which are also isoperibolic calorimetry equipment, acquire specific thermal stability data that can be used for scale-up. Furthermore, the small autoclave tests provide gas evolution data. 

As discussed in chapters 7 and 8, the initial step of the data analysis of a isoperibol calorimetry experiment is the determination of the enthalpy of the isothermal calorimetric process, A//ICp, usually at the reference temperature of 298.15 K. The value of A/Ticp corresponding to any point p along the titration period is given by (recall the discussion of equation 8.1)... 

Another area where titration calorimetry has found intensive application, and where the importance of heat flow versus isoperibol calorimetry has been growing, is the energetics of metal-ligand complexation. Morss, Nash, and Ensor [225], for example, used potenciometric titrations and heat flow isothermal titration calorimetry to study the complexation of UO "1" and trivalent lanthanide cations by tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA), in aqueous solution. Their general goal was to investigate the potential application of THFTCA for actinide and lanthanide separation, and nuclear fuels processing. The obtained results (table 11.1) indicated that the 1 1 complexes formed in the reaction (M = La, Nd, Eu, Dy, andTm)... 

S. R. Gunn. On the Calculation of the Corrected Temperature Rise in Isoperibol Calorimetry. Modifications of the Dickinson Extrapolation Method of Treatment of Thermistor-Thermometer Resistance Values. J. Chem. Thermodynamics 1971, 3, 19-34. 

C. E. Vanderzee. Evaluation of Corrections from Temperature-Time Curves in Isoperibol Calorimetry under Normal and Adverse Operating Conditions. J. Chem. Thermodynamics 1981,13, 1139-1150. 

An important variation of the adiabatic principle is isoperibol calorimetry. Well-defined heat leaks, minimized by efficient calorimeter construction and experiment design, are compensated for by calculation and/or extrapolation. The isoperibol design holds the temperature of the immediate environment surrounding the calorimeter constant. The word isoperibol literally means "constant temperature environment. ... 

The first experiments of gas adsorption calorimetry by Favre (1854) were made with an isoperibol calorimeter. More recently, refinements were introduced by Beebe and his co-workers (1936) and by Kington and Smith (1964). Because of the uncontrolled difference between the temperature of the sample and that of the surroundings, Newton s law of cooling must be applied to correct the observed temperature rise of the sample. In consequence, any slow release of heat (over more than, say, 30 minutes), which would produce a large uncertainty in the corrective term, cannot be registered. For this reason, isoperibol calorimetry cannot be used to follow slow adsorption equilibria. However, its main drawback is that the experiment is never isothermal during each adsorption step, a temperature rise of a few kelvins is common. The corresponding desorption (or lack of adsorption) must then be taken into account and, after each step, the sample must be thermally earthed so as to start each step at the same temperature. In view of these drawbacks,... 

The investigation of polymorphs by practical application of calorimetry cited in the literature employs almost every type of isothermal or isoperibolic calorimetry. The number of polymorphic forms of a crystalline material is dependent on how many different orientations the molecules can be arranged to form a crystal lattice. There is, at present, no way to predict the number of polymorphic forms a material may have. 

To improve the measured AT, in isoperibol calorimetry, the heat losses must naturally be corrected for. Loss calculations are carried out using Newton s law of cooling, written as Eq. (1) in Fig. 4.31 (see also Fig. 4.9). The change in temperature with... 

Wit] C partial enthalpy, enthalpy of formation, isoperibolic calorimetry 1627°C, 0 to 100% Mn, C up to saturation... 

Semi-batch acrylate emulsion polymerization, isoperibolic calorimetry, 434... 

Equations (3.105) and (3.107) for the temperature correction 17), are called the Regnault-Phaundler correction. They assumed the sampling period At to be equal to unity, and thus t"-t = N. This correction is mostly used in isoperibol calorimetry to calculate the corrected tempera-turerise ATc. 

Miles, M.H. and Fleischmann, M. (2008) Accuracy of isoperibolic calorimetry used in cold fusion control experiment. ACS Symposium Series, 198, 153. 

The modeling equation developed by Fleischmann and Pons [2] for isoperibolic calorimetry can be represented by Equation (13.2) [30, 34, 35]... 

Miles, M.H. (2014) Examples of isoperibolic calorimetry in the cold fusion controversy. The Journal of Condensed Matter Nuclear Science, in press. 

The results of the hazardous chemical evaluation are used to determine to what extent detailed thermal stability, runaway reaction, and gas evolution testing is needed. The evaluation may include reaction calorimetry, adiabatic calorimetry, and temperature ramp screening using accelerating rate calorimetry, a reactive system screening tool, isoperibolic calorimetry, isothermal storage tests, and adiabatic storage tests. 

The most important feature for classifying thermal methods is certainly the treatment of the evolved heat. In accumulation methods (adiabatic and isoperibolic calorimetry), the sample is well insulated from its environment and its temperature change is used as a measure of the extent of conversion. In heat transfer or heat flow methods, the evolved heat flow to the environment in... 

Calorimetry with the instrument described in Fig. 4.6 would thus, for example, be characterized as scanning, twin, isoperibol calorimetry, usually less precisely called differential scanning calorimetry (DSC). 

Heat Isoperibolic calorimetry In an isoperibolic ctilorimeter, the temperature of the surroundings remains constant, while the temperature of the sample can differ from the surrounding temperature. 

Wit] High-temperature isoperibolic calorimetry partial mixing enthalpy 1627°C, x(B) up to 50%... 

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