Reaction vessel, calorimeter proper

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

The energy change associated with the process under study induces an energy change of the calorimeter proper, which can be determined by monitoring a corresponding temperature change or heat flux. In some calorimeters the reaction occurs in a closed vessel whose volume does not vary in the course of the experiment. This happens, for example, in bomb combustion calorimetry, where the reaction takes place inside a pressure vessel called the bomb, and in... 

Let us first define a calorimeter as an instmment devised to determine heat. In any calorimeter, we may distinguish 1) the calorimetric vessel (often called the cell, container, or calorimeter proper) at temperature Tc(t), that is usually in good contact with its contents, in which the studied transformation occurs. The contents include the reactant samples and subsidiary accessories necessary to achieve the investigated transformation (e.g. to initiate the reaction, or to mix the reagents) or to calibrate the device and 2) the surroundings at temperature To(t), of-... 

Let the system intended to be studied in the calorimeter be a solution inside a vessel. After the introduction of a second substance, a reaction takes place that has to be followed quantitatively with regard to the production of heat. Obviously, the reaction begins at the site of contact of the two substances and then spreads by diffusion. The heat produced (or consumed) brings about a change of temperature, which in turn causes a heat flow and other effects. A sensor (thermometer) located within or outside the reaction vessel detects a temperature change that occurs with some time lag relative to the reaction proper and can be only loosely correlated with... 

This brief overview of offline measurements can be concluded by considering the measurements of the heat released by chemical reactions, which can be obtained via calorimetric measurements [7, 18]. The most diffused industrial calorimeters are the so-called reaction calorimeters, basically consisting in jacketed vessels in which the reaction takes place and the heat released is measured by monitoring the temperature of the fluid in the jacket. A class of alternative instruments are the scanning calorimeters (differential or adiabatic), in which the analysis is performed by linearly increasing the sample temperature with respect to time, in order to test the reactivity of potentially unstable chemical systems in a proper temperature range by measuring the released heat. 

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