PROCEEDINGS
OF THE TOMSK ORDER OF THE OCTOBER REVOLUTION
AND ORDER OF THE RED BANNER OF LABOR
POLYTECHNIC INSTITUTE named after S. M. KIROV

Vol. 233 1974

APPARATUS FOR STUDYING THE KINETICS OF FAST REVERSIBLE REACTIONS BY THE METHOD OF THE FIELD DISSOCIATION EFFECT USING A RECTANGULAR PULSE

V. I. IVASENKO, V. T. NOVIKOV, V. P. LOPATINSKII

(Presented by the scientific-methodological seminar of the Chemical-Technological Faculty of TPI)

For studying the kinetics of fast reactions in solutions, relaxation methods [1, 2] are widely used, based on shifting the equilibrium in a reacting system by a sharp change in temperature or pressure, or by applying a rectangular voltage pulse. The perturbation time is comparable with the time of chemical relaxation in the system, which makes it possible to study the kinetics of very fast reactions.

These methods have been successfully applied to determine the structure of the hydrated proton [2, 3], the kinetics of complex formation [4, 6], and also to establish reaction mechanisms, especially in enzyme chemistry [6, 9].

The installation schemes described in the literature have a complex system for triggering the oscilloscope and switching the pulses. On the basis of work at the Research Institute of High Voltages of TPI [13], we developed and assembled a scheme of an apparatus for measuring the protonation constants of carboxylic acids. The distinctive features of the apparatus scheme are: 1) a simplified oscilloscope triggering circuit, described in [13, 14]; 2) the use of combined cells; 3) reduction of the pulse rise front by changing the forming line [13].

A description and block diagram of the apparatus are given below and in Fig. 1.

Description of the apparatus

The power supply (1), consisting of an IOM-100/25 transformer, a kenotron, and a filament transformer, makes it possible to obtain a voltage of up to 100 kV. The pulse is formed by discharging a KBG-P capacitor (2) through a forming line (3), consisting of 12 sections of RK-75-4-15 cable, each 30 meters long, with the aid of a controlled spark gap (4). The resulting rectangular pulse is fed to the input of a Winston bridge; one arm of the bridge is the cell (7) with the solution under study, the second is the comparison cell (8), and the others are carbon resistors, the resistance of which is selected so as to be 25–40% of the resistance of cell (7) with the solution under study. The comparison cell (8) is necessary to compensate thermal and polarization phenomena during the discharge in the solution under study. Rempton and co-workers [2] showed that a bifilar-concentration system of cells with complex shielding, previously considered necessary to eliminate the influence of inductance, is not needed if only

Fig. 1. 1. Power supply. 2. KBG-I capacitor.
3. Pulse-forming line. 4. Controlled three-electrode
spark gap. 5. Triggering system. 6. Oscillograph.
7. Cell with the solution under study. 8. Comparison cell

the measured relaxation times are not too small ($\tau \geq 0.3$ μsec). The trimming capacitors [10] also proved unnecessary. The bridge unbalance voltage is fed to an OK-26 or S1-10 oscillograph. The oscillograph is triggered when a voltage is applied to the oscillograph thyratron as the pulse passes through the bridge. Since 0.15 μsec is required to start the sweep, the pulse from the bridge output passes through a delay system. This method of triggering the oscillograph and recording the relaxation time is simpler than those adopted earlier (2, 10–12); we were also able to reduce the pulse rise front to 10 nsec, which reduces the error in measuring the relaxation times.

This circuit makes it possible to determine reaction rate constants on the order of $10^{11}\ \mathrm{mol}^{-1}\ \mathrm{sec}^{-1}$, and also to measure the high-voltage conductivity of electrolytes, which provides valuable information about their structure [11, 12].

Measurements of the protonation constants of halogen-containing acetic acids on the apparatus described above showed good agreement of the results obtained with known data from the literature [15].

REFERENCES

1. M. Eigen; Discuss Faraday Soc., 17, 194, 1954.
2. M. Eigen; De Maeyer; Z. Elektrochem., 59, 986, 1955.
3. M. Eigen; De Maeyer; Proc Roy Soc. A., 247, 505, (1958).
4. Czerlinski, Z. Physik Chem., 19, 240, (1959).
5. Diebler; M. Eigen; Hammes G. G.; Z. Naturforsch., 15B, 554 (1960).
6. R. Alberty, G. G. Hammes. Z. Elektrochem., 64, 124 (1960).
7. M. Eigen; Hammes G. G. Advan Enzymol., 25, 1, 1963.
8. G. G. Hammes; Alberty R. J. Am. Chem. Soc., 82, 1564 (1960).
9. D. N. Haque; M. Eigen. Trans Faraday Soc., 62, 521, 1236 (1966).
10. D. T. Rampton; L. P. Holmes; D. L. Cole; R. P. Jensen; E. M. Eyring. Rev Sci Instr., 38, No. 11, 1637 (1967).
11. G. Atkinson; M. Yokoi. J. Phys Chem., 66, No. 8, 1520 (1962).
12. Bailey; A. Patterson. J. Am. Chem. Soc., 74, 4756 (1952).
13. G. A. Vorob’ev, G. A. Mesyats. Technique for the Formation of High-Voltage Nanosecond Pulses. Energiya, Moscow, 1963.
14. A. A. Vorob’ev, V. Ya. Ushakov, O. P. Semkina, V. V. Ryumin. Prebreakdown phenomena in aqueous electrolytes in ultrahigh pulsed electric fields. Electronic Processing of Materials, No. 2, 1971.
15. E. Caldin. Fast Reactions in Solutions. Mir, Moscow, 1966.