Electrical conductivity of liquid sulfur

Electrical Conductivity of Liquid Sulfur and Sulfur-Phosphorus Mixtures... 

An investigation has been conducted on the electrical conductivities of liquid sulfur and some sulfur-phosphorus mixtures. The purpose of this work was (1) to obtain additional data on the conductivities of liquid semiconductors, which are of theoretical interest, and (2) to investigate the possibility of using these materials as the cathode reactant in lithium-chalcogen electrochemical cells. It is difficult to obtain reliable conductivity data on these systems because of their low conductivities, the strong influence of impurities on their conductivity, and corrosion problems associated with most electrode materials. 

Sulfur vapor consists of a mixture of species that includes S8, S6, S4, and S2 (which like 02 is paramagnetic). Because the S8 molecule is nonpolar, it is soluble in liquids such as CS2 and C6H6. Selenium also consists of cyclic molecules that contain eight atoms, and tellurium is essentially metallic in character. In their vapors, several species are found that contain 2, 6, or 8 atoms. Both are useful as semiconductors, and selenium has been used in rectifiers. Because the electrical conductivity of selenium increases as the intensity of illumination increases, it has been used to operate electrical switches that open or close as a light beam is broken. Selenium was also used in light meters, but other types of meters are now available that are more sensitive. Table 15.1 gives a summary of the properties of the group VIA elements. 

The electrical conductivity a of liquid sulfur increases with temperature except near the viscosity maximum of ca. 170 °C where a minimum of the conductivity is observed. Above 200 °C the plot of log a vs 1/T was found by several authors to be linear but the slopes of these linear relationships as well as the absolute conductivities vary considerably [118-122]. On the assumption that the conductivity at these temperatures is intrinsic, values of about 1.6 eV were derived for the activation energy at high temperatures (up to 900 °C) [121, 122], an energy which is much higher than the activation energy for the formation of free spins by homolytic bond dissociation (see above). 

Fig. 5 Temperature dependence of the electrical conductivity of very pure liquid sulfur [123]...

One cell of a sodium-sulfiir battery is shown schematically in Figure 17.9a. It consists of an inner anode (negative) composed of liquid sodium and an outer cathode (positive) of liquid sulfur (with some added graphite to provide for some electrical conduction). Between the two electrodes is a solid ceramic )3-Al203 electrolyte that allows ions to pass through while keeping the two liquid electrodes separated. The operating temperature of the cell is about 350°C. 

Liquid sulfur dioxide expands by ca 10% when warmed from 20 to 60°C under pressure. Pure liquid sulfur dioxide is a poor conductor of electricity, but high conductivity solutions of some salts in sulfur dioxide can be made (216). Liquid sulfur dioxide is only slightly miscible with water. The gas is soluble to the extent of 36 volumes pet volume of water at 20°C, but it is very soluble (several hundred volumes per volume of solvent) in a number of organic solvents, eg, acetone, other ketones, and formic acid. Sulfur dioxide is less soluble in nonpolar solvents (215,217,218). The use of sulfur dioxide as a solvent and reaction medium has been reviewed (216,219). 

Solutions of hexaphenylethane in liquid sulfur dioxide conduct electricity, suggesting an ionization into triphenylmethyl positive and negative ions. Since the spectrum of triphenylmethide ion was missing from the spectrum of the solution the following equilibrium was postulated ... 

POLAR. Descriptive of a molecule in which the positive and negative electrical charges are permanently separated, as opposed to non-polar molecules in which the charges coincide, Polar molecules ionize in solution and impart electrical conductivity. Water, alcohol, and sulfuric acid are polar in nature most hydrocarbon liquids are not. Carboxyl and hydroxyl groups often exhibit an electric charge, The formation of emulsions and the action of detergents are dependent on tills behavior,... 

Chloro-triphenylmethane constitutes a classical example for distinguishing the ionizing and dissociating ability of a solvent. In 1902, Walden used it in liquid sulfur dioxide in the first demonstration of the existence of carbenium ions [147]. The colourless chloro-triphenylmethane dissolves in liquid sulfur dioxide (fir = 15.6 at 0 °C), giving an intense yellow colour (2max = 430 nm). This is caused by a partial formation of ion pairs, which do not conduct electricity. At low concentrations, the ion pairs partially dissociate into free ions, which do conduct electricity [148, 149]. 

CARBITOL ACETATE (112-15-2) Combustible liquid (flash point 230°F/110°C cc). Incompatible with sulfuric acid, nitric acid, nitrates, strong oxidizers. May attack some pla.stics, rubber, and coatings. Due to low electric conductivity, this substance may generate electrostatic charges as a result of agitation and flow. 

By the sublimation of sulfur hexafluoride in 1933 Denbigh and Whytlaw-Gray (66, 67) found a small liquid residue which they identified as S2Fh>. From 20 liters of crude SF6 gas they recovered only about 20 ml of S2Fio vapor. This method of preparation has been confirmed by others (34, 100, 101, 269, 270, 307). The substance is a colorless volatile liquid which has a surface tension of 13.9 dyne/cm at 0°C. From its vapor pressure, logw Pmm = 7.95 — 1530/T, its heat of vaporization is calculated to be 7000 cal/mole (67). Liquid S2Fi0 has a specific electrical conductivity somewhere between 10 12 and 10 14 ohm-1 cm-1, a dielectric constant of 2.030 at 10° and a density of 2.081, 2.054, and 2.028 gm/ml at 4°, 12°, and 20°, respectively. Its dipole moment is 0 (155). Each sulfur atom is linked octahedrally to five fluorine atoms at a distance of 1.56 A and to the other sulfur atom at a distance of 2.21 A (7, 129). 

Hall electrolytic conductivity detector An element-selective GC detector primarily intended for trace analysis of organic compounds containing chlorine, nitrogen, or sulfur. In operation, this detector pyrolyzes the column effluent gas into soluble electrolytes that are dissolved in a stream of deionized liquid. The observed change in electrical conductivity, proportional to the amount of material present, is measured. 

Liquid sulfur dioxide expands by about 10% when warmed from 20 °C to 60 °C under pressure. Pure Uquid sulfur dioxide is a poor conductor of electricity, but high conductivity solutions of some salts in sulfur dioxide can be made. Liquid sulfur dioxide is only sUghtly miscible with water. 

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