potentials and the dependence of the degree of coverage on the potential for different concentrations of $\beta$-naphthol in the solution. Analysis of the isotherms obtained showed that the adsorption of $\beta$-naphthol on mercury obeys the Frumkin isotherm.

From the experimental adsorption isotherms, the attraction constants were then calculated, and a linear dependence of these quantities on the potential was established.

From the $\varepsilon,\psi$ curves ($\varepsilon$ is the electrode charge, found by integrating the differential-capacitance curves) and the $\zeta\psi$ curves recorded in diluted background solutions, the dependence of the adsorption jump in potential on the degree of coverage was found. The character of this dependence is similar to the regularity of the change in the $\psi_1$ potential with the degree of coverage during adsorption of $\beta$-naphthol from 0.1 N $H_2SO_4$.

References

1. M. A. Gerovich. DAN SSSR, 96, 543 (1954); 105, 1278 (1955).
2. Yu. N. Oblivantsev, T. V. Gomza, V. E. Gorodovykh. Advances in Polarography with Accumulation. TSU, Tomsk, 1973, p. 101.
3. B. B. Damaskin. Zh. fiz. khim., 32, 2199 (1968).
4. B. B. Damaskin, O. A. Petrii, V. V. Batrakov. Adsorption of Organic Compounds on Electrodes. Moscow, “Nauka,” 1968.

INVESTIGATION OF THE EFFECT OF $\beta$-NAPHTHOL ON THE KINETIC PARAMETERS OF THE CADMIUM DISCHARGE–IONIZATION REACTION BY THE FARADAIC IMPEDANCE METHOD

Yu. N. Oblivantsev, V. E. Gorodovykh

In the present work, the effect of the structure of the adsorption film of $\beta$-naphthol on the kinetic parameters of the cadmium discharge–ionization reaction was studied by the Faradaic impedance method.

Measurements were carried out on an amalgam dropping electrode in two supporting electrolytes—neutral (1 M $Na_2SO_4$) and acidic (0.1 N $H_2SO_4$). A platinum cylinder, positioned symmetrically with respect to the working electrode, was used as the auxiliary electrode. Cadmium amalgam was prepared by electrolysis of an acidified solution of 1 M cadmium sulfate with soluble cad-

with a copper anode in an argon atmosphere. The components of the electrode impedance were determined using an R-568 AC bridge at frequencies from 100 Hz to 100 kHz.

In an acidic supporting electrolyte, the charge-transfer resistance of the cadmium discharge–ionization reaction was found by graphical analysis of the electrode impedance /1/. The dependence in \(X-R\) coordinates (\(X\) is the reactive component, \(R\) the active component of the electrode impedance) in the presence of \(\beta\)-naphthol in the solution has the form of semicircles, which indicates the irreversible character of the cadmium discharge–ionization reaction under these conditions. Additional confirmation of the correctness of this conclusion is provided by the rectilinear character of the dependence in \(C_M-\omega^{-2}\) coordinates (\(C_M\) is the bridge capacitance, \(\omega\) is the angular frequency).

In a neutral supporting electrolyte, the \(X-R\) dependence is a combination of a semicircle with a straight line for all concentrations of \(\beta\)-naphthol in the solution, which indicates a quasi-reversible character of the reaction.

From the values of the charge-transfer resistance of the reaction, the dependence of the exchange current (\(i_0\)) on the concentration of \(\beta\)-naphthol in neutral and acidic supporting electrolytes was found. The transfer coefficients were determined graphically from the dependence of the exchange current on the concentration of the oxidized and reduced forms of the reaction participants in the solution and amalgam. The data obtained are given in Table 1.

Table 1

Kinetic parameters of the cadmium discharge–ionization reaction
in the presence of \(\beta\)-naphthol

As can be seen from the table, the exchange current and the rate constant of the reaction on the neutral background, which corresponds to a flat orientation of the $\beta$-naphthol molecules at the interface /2/, decrease with increasing $\beta$-naphthol concentration within one order of magnitude, whereas on the acidic background (inclined orientation of the adsorbate molecules) they decrease by two and a half orders of magnitude. These data confirm the conclusion made above about the irreversible character of the cadmium discharge–ionization reaction on the acidic background and its quasi-reversible character on the neutral background.

Using the values of the degree of filling of the electrode surface $(\theta)$ /2/ that we found from adsorption measurements, dependences of the degree of inhibition of the exchange current $\Delta i_0/i_0$ on $\theta$ were constructed for the neutral and acidic backgrounds. On the neutral background the degree of inhibition of the reaction at all degrees of filling is less than $\theta$, and at $\theta = 0.8$–$0.9$ the exchange current reaches an almost constant value (see table). This indicates that, in the case of a flat orientation of the adsorbate molecules, the cadmium discharge–ionization reaction proceeds at a noticeable rate on the occupied surface.

On the acidic background the dependence $\Delta i_0/i_0$ has an S-shaped form, and at $\theta > 0.5$ the degree of inhibition becomes greater than the degree of filling, while the exchange current decreases sharply. Such a pronounced difference in the dependences of $\Delta i_0/i_0$ is, in all probability, explained by the strengthening of the adsorption film of $\beta$-naphthol at the interface as a result of an increase in the fraction of vertically oriented molecules upon transition from the neutral to the acidic background.

Literature

1. B. B. Damaskin. Principles of Modern Methods for Studying Electrochemical Reactions, Moscow State University, 1965.
2. Yu. N. Oblivantsev, V. E. Gorodovykh, present collection.

INVESTIGATION OF THE EFFECT OF BENZYLAMINE ON ELECTRODE PROCESSES INVOLVING CADMIUM, COPPER, ZINC, AND LEAD IONS

V. E. Gorodovykh, L. M. Smolova

The presence in the analyzed solution of organic surface-active substances (SAS) most often leads to a decrease—