Isoperibolic Reaction

Figure 8.1 Scheme of a Dewar vessel isoperibol reaction-solution calorimeter. A ampule containing the sample B ampule breaking system C calorimeter head D temperature sensor E stirrer F electrical resistance G Dewar vessel H plunger of the ampule breaking system I, J inlets K plug connecting the calibration resistance to the calibration circuit. 

Figure 8.2 Scheme of a typical calibration circuit used in isoperibol reaction-solution calorimetry. P power supply S switch R- electrical resistance inside the calorimetric vessel (F in figure 8.1) R2 standard resistance. 

Figure 8.3 Typical temperature-time curves obtained when two calibrations are made in isoperibol reaction-solution calorimetric studies of (a) an exothermic reaction and (b) an endothermic reaction. A fore period of the first calibration experiment B main period of the first calibration experiment ...

The enthalpy of the reverse of reaction 10.17, the cis - trans isomerization reaction is thermally activated and thus can be determined by isoperibol reaction-solution calorimetry (however, because the reaction is slow, a catalyst must be used). These experiments were also made by Dias et al. and led to -49.1 1.0 kJ mol-1 for reaction 10.18. 

The safety assessment for isoperibolic reactions is essentially the same as for isothermal reactions. Since the initial temperature of the reaction mass is often equal to the temperature of the cooling system, the MTSR may be calculated in the same way by using Equation 6.12. The thermal stability of the reaction mass must be ensured at this temperature (MTSR). 

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