ELECTRICAL CONDUCTIVITY OF THE ANILINE—ANTIMONY TRICHLORIDE SYSTEM

A. S. NAUMOVA and S. F. ZHITKOV

The antimony chloride—aniline system was studied by Menshutkin [3] by the method of thermal analysis. He established the presence in the system of five compounds of antimony chloride with aniline, three of which are thermally the most stable and melt without noticeable decomposition. Krotkov [9] constructed viscosity isotherms for this system. The curves pass through a maximum at 50 mole percent, indicating the formation of only one compound, $\mathrm{C_6H_5N_2H_2 \cdot SbCl_3}$. The results of studying viscosity and fusibility thus show that this system is an example of systems for which the indications of diagrams of the properties studied are not the same. The fusibility diagram establishes the presence in the system of five compounds, whereas on the viscosity curve only one, thermally more stable, compound is reflected.

It is known that phenomena of a similar kind [1] occur not only in the case of diagrams of the indicated properties, but also of others; moreover, discrepancies may concern not only the number of compounds, but also their composition [2,5]. In order to detect the presence in a system of all newly formed compounds, it is necessary to study a series of properties.

In the opinion of M. I. Usanovich [6], the curves of the temperature coefficient of electrical conductivity give indications of the composition of the compounds formed in a system. It was of interest to trace whether the compounds discovered by thermal analysis of the antimony chloride—aniline system would be reflected in diagrams of electrical conductivity and of its temperature coefficient.

Experimental Part

The substances investigated were carefully purified and stored in sealed ampoules. Aniline was first dried with caustic potash, then with metallic sodium, over which it was also distilled. For the work, the fraction with a boiling point of 180–181° at 752 mm pressure was taken. Antimony trichloride was obtained from antimony pentachloride by reduction with metallic antimony. The antimony trichloride thus obtained was purified by distillation and subsequent fractional freezing in sealed ampoules. The melting temperature of $\mathrm{SbCl_3}$ was 73.3°C.

Electrical conductivity was measured by the usual Kohlrausch method at 65°C and at those temperatures (95° and 125°) at which the viscosity of the system had been studied, in order to be able to compare our data with the data of previous authors.

The results of measuring the specific electrical conductivity of the $\mathrm{SbCl_3}$—$\mathrm{C_6H_5NH_2}$ system and the values of its relative temperature coefficient are summarized in Table 1 and presented graphically in Figures 1 and 2.

Table 1

Figure 1 shows that the isotherms of specific electrical conductivity are irrational and have a form analogous to the isotherms of specific electrical conductivity obtained by M. Usanovich [8] and F. Terpugov [4] for the system AsCl₃—\((\mathrm{C_2H_5})_2\mathrm{O}\).

In the region of higher antimony chloride content (Fig. 1), the curves pass through a maximum, reaching considerable values at 125°.

Fig. 1

(\(\sim 2 \cdot 10^{-2}\) reciprocal ohms). As the temperature changes, the curves of specific electrical conductivity undergo deformation. The inflection present on the isotherm at 125°, with decreasing temperature, gradually disappears, becoming at 65° a diffuse minimum located near 50 mole percent. This latter fact is some indication of the formation of an equimolecular compound between the components of the system.

The curve of the temperature coefficient of electrical conductivity (Fig. 2) passes through a maximum at 50 mol. percent, i.e., corresponds to the ordinate of the compound \(C_6H_5NH_2 \cdot SbCl_3\).

In order to trace the course of the electrical conductivity independently of viscosity, we, using Krotkov’s data, eliminated the influence of this factor.

Fig. 2

The results of the calculations are given in Table 2 and represented graphically in Fig. 3. It follows from the figure that the isotherms of the corrected electrical conductivity have a smooth course, thus indicating a substantial influence of viscosity on the course of the electrical-conductivity isotherms, which are thereby considerably distorted.

Table 2

In Figs. 4 and 5 are shown the isotherms of the molecular electrical conductivities (the density values were taken from Krotkov’s work). The curve in Fig. 4 of the molecular electrical conductivity, calculated for \(SbCl_3\) as the electrolyte,

(Table 3), has a sharply anomalous character, thus confirming that in these solutions the electrolytes are complex compounds formed as a result of interaction of the components of the system [7,10].

Fig. 3

Table 3

| Wt. % SbCl₃ | \multicolumn{4}{c}{Molecular electrical conductivity} |
|---:|---:|---:|---:|---:|
| | $V_{95}^{\circ}$ | $\mu_{95}^{\circ}$ | $V_{125}^{\circ}$ | $\mu_{125}^{\circ}$ |
| 6.52 | 3498 | 0.5040 | 3644 | 0.4876 |
| 10.22 | 2167 | 0.5790 | 2254 | 0.8522 |
| 27.70 | 686.3 | 0.9919 | 709.9 | 1.6510 |
| 35.10 | 507.7 | 0.9195 | 524.1 | 1.7010 |
| 52.58 | 283.6 | 0.5518 | 291.2 | 1.2830 |
| 57.54 | 243.2 | 0.4813 | 250.9 | 1.2290 |
| 64.66 | 201.6 | 0.3343 | 206.3 | 1.1540 |
| 70.66 | 171.7 | 0.4071 | 176.4 | 1.3100 |
| 73.88 | 157.5 | 0.5346 | 162.5 | 1.5260 |
| 79.86 | 136.0 | 0.7552 | 140.0 | 1.7520 |
| 80.92 | 132.3 | 0.8287 | 136.2 | 1.9010 |
| 82.97 | 126.7 | 0.9358 | 130.9 | 2.017 |
| 88.67 | 110.4 | 1.4580 | 113.8 | 2.316 |
| 94.83 | 96.60 | 1.2820 | 96.60 | 1.777 |
| 98.62 | 88.90 | 0.7791 | 91.42 | 1.245 |

The isotherms of molecular electrical conductivity, calculated with respect to aniline as the electrolyte, are presented in Fig. 5, and their values are collected in Table 4.

The curve in Fig. 5 has a less anomalous character, rising smoothly over almost its entire length.

Fig. 4

Fig. 5

Table 4

Molecular electrical conductivity

From the experimental data presented it follows that both the diagram of specific electrical conductivity and the diagram of its temperature coefficient reflect the presence of only one most stable compound of composition \(C_6H_5NH_2 \cdot SbCl_3\), whereas, judging from Menshutkin’s fusibility diagram, one might have expected the reflection of still another, comparatively strong compound \((SbCl_3 \cdot 2C_6H_5NH_2)\), especially on the curve of the temperature coefficient of electrical conductivity, on which the result of the chemical interaction of the components of the system is manifested more fully and sharply [6]. All the other compounds established by thermal analysis give no “special” points on the diagrams presented.

Conclusions

1. The electrical conductivity of the system \(SbCl_3—C_6H_5NH_2\) has been studied at \(65^\circ\), \(95^\circ\), and \(125^\circ\).

2. The molecular electrical conductivity, calculated with respect to \(SbCl_3\) as the electrolyte, has a sharply expressed anomalous character.

3. The curve of the temperature coefficient of electrical conductivity passes through a maximum at 50 molecular percent, indicating the existence in the system of the compound \(C_6H_5NH_2 \cdot SbCl_3\), the presence of which is also reflected in the isotherms of electrical conductivity in the form of a minimum that changes and shifts with temperature.

Literature

1. N. S. Kurnakov—Introduction to Physicochemical Analysis, p. 336, 1940.
2. B. P. Kondratenko—ZhOKh, 4, p. 246. 1934.
3. V. N. Menshutkin—ZhRKhO, 44, p. 1128. 1928.
4. F. I. Terpugov—ZhOKh, 2, p. 865. 1932.
5. M. I. Usanovich—ZhFKh, 6, p. 923. 1935.
6. M. I. Usanovich—Protocols of the meetings of the Leningrad Chemical Society for 1932, p. 25; Proceedings of the VI Mendeleev Congress, II, issue 2, p. 174.
   M. I. Usanovich and F. Terpugov—ZhOKh, 2, p. 447. 1932.
   M. I. Usanovich—ZhOKh, 11, p. 773. 1941.
7. M. Usanovich—Reports of the Academy of Sciences of the USSR, 1, p. 518. 1935.
8. M. Usanovich—Zeitschr. phys. chem. A. 140. 429. 1929.
9. Kurnakov N. S.—Zeitschr. f. anorg. u. allgem. chem. 135. 81. 1924.
10. Rabinowitch—Zeitschr. phys. chem. 99. 338. 1921. 99, 443. 1921.