Pressure-jump apparatus with conductivity detection

A pressure perturbation results in the shifting of the equilibrium the return of the system to the original equilibrium state (i.e., the relaxation) is related to the rates of all elementary reaction steps. The relaxation time constant associated with the relaxation can be used to evaluate the mechanism of the reaction. During the shift in equilibrium (due to pressure-jump and relaxation) the composition of the solution changes and this change can be monitored, for example by conductivity. A description of the pressure-jump apparatus with conductivity detection and the method of data evaluation is given by Hayes and Leckie (1986). 

Kinetic experiments were conducted using a pressure-jump apparatus with conductivity detection. Details of the apparatus and its operation can be found in Appendix A. Sample equilibration time can have an effect on the kinetic results (e.g., slow processes (on the order of hours-days) occurring concurrently but not monitored in the time frame of the p-jump technique (milllseconds-seconds)) hence, it is important to run kinetic experiments on samples with similar equilibration history. All samples were equilibrated between 3 and 4 hours for the p-jump kinetic studies. The temperature of the p-jump apparatus, which includes sample and reference solution cells, was maintained at 25.0°C 0.1°C. 

Pressure-Jump Apparatus with Conductivity Detection... 

Figure 2.4 Block diagram of the p-jump apparatus with conductivity detection and the twin cell arrangement from Dialog (Germany). A, autoclave Ci and C2, conductivity cells E, electrodes M, elastic membrane D, metal diaphragm P, pressure pump m, manometer G, 40 kHz generator driving the conductivity bridge Cg and C4, tunable capacitors and Rj, helipot resistances Rg, potentiometer Os, oscilloscope (now replaced by a computer).

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