Measurements of electrical conductivity in solid bromine and iodine

The refractive indices and absorption edges of liquid bromine and iodine have been measured over the temperature ranges 19 to 57°C and 114 to 181°C respectively, and at wavelengths from the absorption edge (700 nm in bromine and 1100 nm in iodine) up to 1800 nm. At 1800 nm the indices are 1.604 in bromine at 19°C, and 1·934 in iodine at 114°C; both liquids are strongly dispersive. The temperature dependence of the refractive index appears to result largely from the thermal expansion of the liquids, and is fairly well accounted for by the Lorenz-Lorentz equation. The absorption edges in both liquids show well-defined exponential regions; neither the positions nor the slopes of the edges depend strongly on temperature. The optical properties of liquid bromine show little evidence of molecular interactions; in liquid iodine they are significant but not dominant. The experimental data on molecular electronic polarizabilities are in good agreement with calculated values.

The optical properties of liquid bromine and iodine

The absorption spectra in the ultraviolet and visible region were measured as a function of the temperature for pure molten I2 and for I2+Te solutions. The two peaks found at about 305 and 370 mμ can be attributed to the I3− ion. These peaks increase with the addition of Te indicating an increase in the concentration of the I3− ion. This result is consistent with the previous interpretation of the conductivity of molten I2 containing Te. The ionization potential of I3− can be estimated to be about 3.1 eV on the basis of a cyclic analysis using the model of Stein and Treinin which was developed for anion spectra in aqueous solutions. The temperature shift of the absorption energy can also be interpreted in terms of the same model. The heat change for the I2(g)+I(g)=I3(g) reaction is estimated as −48.0 kcal·mol−1.

Spectra of Anions in Pure Iodine Melt and Iodine Solution Containing Tellurium

Density measurements of liquid iodine from the melting curve up to 1000°C and 200 MPa are reported. The measurements have been performed in an internally heated autoclave by a dilatometric method. The results indicate, that liquid iodine remains a normal molecular liquid along its liquid-vapour coexistence curve. The observed strong curvatures of the isochores at high pressures and high temperatures are consistent with the assumption of a formation of strongly localized charged centers resembling a partial dissociation of iodine into solvated ions.

The Equation of State of Dense Liquid Iodine up to 1000°C and 200 MPa

Measurements of electric conductance as a function of temperature have been made for the pure liquids; I2, SbCl3, SbBr3 and SbI3, and the mixtures ; I2+SbI3 and SbBr3+SbI3, from 100 to 250°C. Furthermore, measurements of density by a pycnometric method as a function of temperature have also been made for these mixtures, from 100 to 300°C. The conductivities of these liquids lie in the range from 5×10−4 to 1×10−5 ohm−1 cm−1, and are about 10−4 times lower than those of alkali halide melts. In these poorly-conducting pure liquids, the molecules may be considered as constituting a solvent in which slightly dissociated ions are contained. The negative temperature coefficient of conductivity for iodine is in marked contrast to the antimony halide melts, and may be interpreted in terms of the ionic conduction and electron hopping mechanism rather than the metallic one.

ShimojiMitsuo

Papers

Electric Conductance and Density of Molten Salt Systems: I2+SbI3, SbBI3+SbI3, and SbCl3