Calorimeter reaction vessel

L. D. Hansen, T. E. Jensen, S. Mayne, D. J. Eatough, R. M. Izatt, J. J. Christensen. Heat-Loss Corrections for Small Isoperibol Calorimeter Reaction Vessels. J. Chem. Thermodynamics 1975, 7, 919-926. 

A liquid serves as the calorimetric medium in which the reaction vessel is placed and facilitates the transfer of energy from the reaction. The liquid is part of the calorimeter (vessel) proper. The vessel may be isolated from the jacket (isoperibole or adiabatic), or may be in good themial contact (lieat-flow type) depending upon the principle of operation used in the calorimeter design. 

FIGURE 3.2 Diagram of a calorimeter. The reaction vessel is completely submerged in a water bath. The heat evolved by a reaction is determined by measuring the rise in tem-peratnre of the water bath. 

Figure 6.1 Examples of calorimeters in which the calorimeter proper (a) contains the reaction vessel and (b) coincides with the reaction vessel.

The experimental procedure was as described, the only difference being that a capillary containing a suitable amount of I2 was dropped into the reaction vessel (and the calorimeter allowed to stabilize) before the Cr(CO)6 sample was dropped. After recording the thermogram corresponding to reaction 9.15, the cell was removed and the contents analyzed to determine n (which varied from 0.30 to 0.38 in five separate experiments). 

It is possible that only a fraction of the radiant energy supplied to the calorimeter would be absorbed by the reaction mixture. Part of that radiation can be reflected (Er) and, if the reaction vessel is transparent, another fraction can be transmitted to the surroundings (Et). Furthermore, the electronically excited states of the reactants may decay by luminescence, so more energy (E ) may be lost to the surroundings. If these three contributions are taken into account, equation 10.1 becomes... 

The value of e0 is only constant for a fixed volume V of solution inside the calorimetric vessel. The change of e0 with V is primarily due to an increase of the reaction vessel wall in contact with the liquid as the liquid volume increases [ 197,200]. This change, de0/dV, which is constant for well-designed calorimeters [197,200], can be determined by measuring e0 as a function of V. Because it has been found that as expected, e0 and d 0/dV are independent of the nature of the liquid used in the calorimeter, they are normally determined by performing electrical calibrations with the calorimeter filled with different volumes of water [200]. The energy equivalent of the calorimeter at any point during a titration can therefore be calculated from... 

Use of medium-scale heat flow calorimeter for separate measurement of reaction heat removed via reaction vessel walls and via reflux condenser system, under fully realistic processing conditions, with data processing of the results is reported [2], More details are given elsewhere [3], A new computer controlled reaction calorimeter is described which has been developed for the laboratory study of all process aspects on 0.5-2 1 scale. It provides precise data on reaction kinetics, thermochemistry, and heat transfer. Its features are exemplified by a study of the (exothermic) nitration of benzaldehyde [4], A more recent review of reaction safety calorimetry gives some comment on possibly deceptive results. [5],... 

Transfers of energy as heat are measured with a calorimeter, a device in which transfers of energy as heat are monitored by observing changes in temperature. A simple calorimeter consists of a reaction vessel... 

Most of the existing reaction calorimeters consist of a reaction vessel and a surrounding jacket with a circulating fluid that transports the heat away from the reactor (see Fig. 8.1)... 

If a heat conduction calorimeter is left for some time and no process takes place in the reaction vessel, there will, ideally, be no temperature gradients in the system made up by vessel, thermopile, and heat sink. The thermopile potential, U, which is proportional to the temperature difference between vessel and heat sink will thus be zero. If a reaction takes place in the vessel and heat is produced (or absorbed), the temperature of the vessel will increase (decrease) leading to 17 0 (see Figure 4). The temperature gradient will cause the heat evolved in the vessel to flow through the thermopile to the heat sink or, in case of an endothermic process, in the... 

Equation (17) is usually called the Tian equation. In cases where significant temperature gradients are present within the reaction vessel, two or more time constants must be used. When the change in rate of a process is small, the value for X(dU/dt) will often be insignificant compared to the value for U (equation (17)). With heat conduction calorimeters used in work on cellular systems, this is typically the case and the heat production rate is then, with a good approximation, given by the simple expression... 

Thus, in the ideal case and for a given type of thermopile, the sensitivity of the calorimeter is independent of the number of thermocouples in the thermopile wall. Furthermore, and in contrast to adiabatic instruments, the sensitivity of a thermopile heat conduction calorimeter is independent of the heat capacity of the reaction vessel and its content. 

In flow calorimeters, samples of a culture grown in a bioreactor are continuously pumped through the measuring cell of a microcalorimeter. The sensitivity of the differential signal between the reaction vessel and the reference vessel is comparable to that obtained from microcalorimetry, e.g. [193]. From a practical point of view, they are quite flexible because they can be connected to any reactor but, due to transfer times in the minute(s) range, gas and substrate limitations must be considered. 

The data derived from calorimetric measurements reflect acoustic power delivery for fairly well matched loads. This is not always the case under normal working conditions. If the calorimeter is used as reaction vessel, and if a matching system is used, the difference in acoustical impedance between the medium inside the calorimeter and the coupling liquid must be known in order to introduce a correction factor. 

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