Titration calorimetry isoperibol continuous

The principles of titration calorimetry will now be introduced using isoperibol continuous titration calorimetry as an example. These principles, with slight modifications, can be adapted to the incremental method and to techniques based on other types of calorimeters, such as heat flow isothermal titration calorimetry. This method, which has gained increasing importance, is covered in section 11.2. 

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) 

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 

Equation 11.4 is usually applied under the assumption that ideal mixing occurs, that is, V = Va + Vg. As mentioned, this is a good approximation provided that diluted solutions of titrant and titrate are used. 

Method 1 is the more accurate from the two methods because the energy equivalent of the calorimeter is directly measured as a function of V for each system under study. Method 2 is less time-consuming because once s0 and ds0/dV have been determined, no further calibrations are necessary as long as the data needed to evaluate sc are available. 

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Figure 11.2 shows a typical temperature-time curve for a continuous isoperibol titration calorimetry experiment involving an exothermic process. In the initial and final periods (between points a and b, and c and d, respectively), the observed temperature change is determined by the heat of stirring, the heat dissipated by the temperature sensor, and the difference between the temperature of the calorimetric vessel and the temperature of the thermostatic bath. The titration... 

Titration calorimetry or thermometric titration calorimetry is a technique in which one reactant is titrated continuously into the other reactant, and either the temperature change or heat produced in the system is measured as a function of titrant added. In isoperibol titration calorimetry, the temperature of a reaction vessel in a constant-temperature environment is monitored as a function of time (Figure 8.4) (Hansen et al., 1985 Winnike, 1989). A single titration calorimetric experiment yields thermal data as a function of the ratio of the concentrations of the reactants. 

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