decreased by several degrees. However, the pour point returned to its initial value one hour after mechanical stirring, which quite definitely indicates the role of thixotropic structures in the loss of mobility by oil.

Conclusions

1. It has been shown that the pour point of West Siberian oils decreases in the presence of petroleum acids, increases with increasing paraffin content, and returns to its initial value after some time following mechanical stirring, which indicates the role of thixotropy in oil solidification.

2. It has been established that, for the oils studied, the duration of preservation of the temperature depression is several days.

References

1. S. S. Nametkin. Chemistry of Petroleum. Moscow, Publishing House of the Academy of Sciences of the USSR, 1955, p. 46.

2. T. P. Zhuze. “Colloid Journal,” 1950, 12, no. 4, 265–274.

3. O. M. Al’chikov, V. P. Konovalov. Proceedings of the Institute of Petroleum Chemistry and Natural Salts, Academy of Sciences of the Kazakh SSR, 1971, no. 3, pp. 96–99.

4. Kh. A. Akhmedzhanov, B. U. Urazgaliev, O. M. Al’chikov. Proceedings of the Institute of Petroleum Chemistry and Natural Salts, Academy of Sciences of the Kazakh SSR, 1970, no. 1, pp. 46–49.

On the Analysis of the Temperature Dependence of Anodic Peaks in the APN Method

S. N. Karbainova

Previously /1–5/ we studied the temperature dependence of the height \((i)\) and coefficient of the anodic peak \((K_a)\), the half-peak width \((b_{1/2})\), and the peak potential \((\psi_n)\) over a wide range of rates of change of potential \((W)\) and electrode dimensions, both for a mercury film electrode \((\ell\)—thickness of the mercury film) and for a stationary mercury drop electrode \((r\)—drop radius). The results of these studies made it possible to reveal the complex character of the temperature dependence of the above-

knowledge of the characteristics of the anodic peak, and also to obtain a number of recommendations important in practical terms for the use of elevated temperatures in the method of amalgam polarography with accumulation (APN).

The question of the temperature dependence of the height, potential, and width of the half-peak is determined by the conditions under which the experiment is carried out (the dimensions of the electrode, the stirring rate, etc.).

In practical work, when determining traces of various elements, it is advisable to raise the temperature of the solution being analyzed only at the stage of preliminary electrolysis. The subsequent dissolution of the metal from the amalgam is more expediently carried out at room temperature of the solution, since under conditions of elevated temperatures, with high sensitivity of the instrument (e.g., \(10^{-9}\) A/mm), it is very difficult to obtain sufficiently reproducible results because of the large residual current, convection currents in the solution being analyzed, etc.

The use of elevated temperatures at the stage of anodic dissolution of the metal from the amalgam under the working conditions of the APN method does not lead to a noticeable increase in sensitivity when a stationary mercury drop electrode is used. In the case of a mercury film electrode, the sensitivity of the method, on the contrary, decreases.

The degree to which the height of the anodic peak increases with temperature depends significantly on the magnitude of the activation energy of the diffusion process of the metal ions in the given electrolyte, i.e., on the nature of the solvent.

Thus, theoretical and experimental studies of the dependence of the anodic-peak height on temperature make it possible to establish not only the optimal working conditions when elevated temperatures are used, but also to reveal the limitations, in some cases, on the use of this procedure.

For a quantitative assessment of the nature of the influence of temperature on anodic peaks in APN, the simple relations (1, 2, 3), obtained in works /1–3/, may be used; these relate the coefficient of the anodic peak, the half-peak width, and the peak potential to various parameters of the anodic

of the process through the theoretical parameter

\[ \gamma=\frac{RT}{F}\cdot \frac{1}{\ell^{2}}\cdot \frac{D_R}{zW}; \]

\[ K_a=\frac{K_0}{(1+1.8\gamma)^{1/2}}, \tag{1} \]

where

\(K_0\) is the value of the coefficient of the reversible anodic peak under conditions of linear semi-infinite diffusion

\[ \left(K_0=0.446\,\frac{z^{3/2}\cdot F^{3/2}}{R^{1/2}\cdot T^{1/2}}\cdot D^{1/2}\cdot W^{1/2}\right). \]

\[ \frac{\theta_{1/2}-38.3}{101.3-\theta_{1/2}}=\frac{0.09}{\gamma^{1.2}}. \tag{2} \]

\[ \varphi_n-\varphi_{1/2}=a+b\lg \frac{1}{\gamma}. \tag{3} \]

The formulas obtained satisfy the limiting cases arising from the rigorous theory of reversible anodic peaks and make it possible, using only one dimensionless variable \(\gamma\), to take into account the influence of various factors on the height and shape of anodic peaks when the electrode process proceeds reversibly.

It has been proposed to use relations (1–3) for an approximate evaluation of the degree of reversibility of the electrode process of metal oxidation from an amalgam. For example, it is not difficult to estimate the theoretical value of the coefficient of the reversible anodic peak for given parameters of the anodic process over a wide range of \(\ell\), \(W\), and \(T\). This value \(K_A\) can serve as a quantity on the basis of which, by comparing it with the experimental value, one may make an assumption about the degree of reversibility of the electrode process.

It should be emphasized that the study of the influence of temperature on the rate of an electrode reaction is associated with considerable difficulties. In the present work the influence of temperature on the principal characteristics of the anodic peak, which are of the greatest practical interest in the APN method, has been studied. However, even in this part of the work the experimenter encounters certain difficulties. Indeed, in studies using mercury as the reference electrode in two electrolyzers, we successfully avoided, for example, the distorting influence of thermodiffusion potentials (TDP); however, the zero conditions, relative-

for which the potentials of the anodic peaks were measured is, in this case, not the same for different temperatures. Conversely, when a saturated calomel electrode is used at constant temperature, the results of the investigations are distorted to some extent by the thermoelectric emf that arises. Therefore, in the experimental part of the work all values of the anodic-peak potentials were given not on the potential scale, but were treated relative to the half-wave potential at the same temperature, which allowed us to eliminate the distorting influence of thermodiffusion potentials and to obtain satisfactory agreement between the experimental data and the calculations.

References

1. S. N. Karbainova, A. G. Stromberg, Yu. A. Karbainov. Elektrokhimiya, 10, 1409, 1971.
2. S. N. Karbainova, A. G. Stromberg. Elektrokhimiya, 10, 1488, 1971.
3. S. N. Karbainova. Collection of Works of Young Scientists. Chemistry and Chemical Technology. Tomsk, 1973, 19.
4. Yu. A. Karbainov, S. N. Karbainova, A. G. Stromberg. Elektrokhimiya, 2, 220, 1973.
5. A. G. Stromberg, S. N. Karbainova, Yu. A. Karbainov. “Zavodskaya laboratoriya,” 3, 257, 1970.

INVESTIGATION OF THE EFFECT OF AN ELECTRIC FIELD ON HEAT TRANSFER AND HYDRAULIC RESISTANCE IN A FLOW

I. P. Chashchin, V. P. Ignatov

Heat transfer occupies a leading place in industry; therefore, questions connected with the intensification of heat-transfer processes are at the center of attention of many researchers.

Along with traditional methods for intensifying heat transfer, such as turbulizing inserts, finning, etc., methods are being proposed for intensifying heat transfer by electric fields.

A number of authors indicate that electric fields are a powerful factor in heat- and mass-transfer processes.

We have carried out studies to investigate the influence of nonuni-