Selenium specific heat

Tarassov (1955) and also Desorbo (1953) have considered these ideas in relation to a onedimensional crystal in which case the one-dimensional frequency distribution function predicts a T dependence of the specific heat at low temperatures. In the case of crystalline selenium, however, it has been found necessary to combine the one-dimensional theory with the three-dimensional Debye continuum model in order to obtain quantitative agreement with the data below about 40° K. Tem-perley (1956) has also concluded that the one-dimensional specific heat theory for high polymers would have to be combined with a three-dimensional Debye spectrum proportional to T3 at low temperatures. For a further discussion of one-dimensional models see Sochava and TRAPEZNrKOVA (1957). 

Desorbo, W. The specific heat of crystalline selenium at low temperatures. J. Chem. Phys. 21, 1144-1148 (1953). 

Cuprous selemde, Cu2Se.—The selenide occurs as the mineral berzelianite. It is produced by direct combination of copper and selenium-vapour, and is a dimorphous substance of stccl-grey colour, the transition-point for the two forms being 110° C. At 20° C. its specific heat is 0-1047,3 and its heat of formation 20-8 Cal ... 

Magnetic susceptibility (I8°) —0.31 x 10-( cgs. Hardness (Mohs) 2,3. Modulus of elasticity 6,000,000 psi. Specific heat (solid) 0.047 cal/g/"C. Thermal conductivity 0.014 at 20°, Burns in air with a greenish -blue flame, forming the dioxide. Insol in water, in benzene, in carbon disulfide. Not attacked by hydrochloric acid reacts with nitric acid with coned or fuming sulfuric acids, forming a red soln in presence of air dissolves in potassium hydroxide with formation of a deep-red sola. Combines with the halogens does not react with sulfur or selenium. 

The DTA curves show no evidence for a Tp mechanism in the case of liquid selenium. The specific heat at constant pressure, Cp, vs. T curve of liquid selenium shows a minimum near 500°C . The increase after this minimum is ascribed to depolymerization, which is endothermic. However, care must be exercized in determining the polymer-ring equilibrium mechanism from the heat capacity measurements. The following contribute to the specific heat ... 

Concerning AFS, the atomiser can be a flame, plasma, electrothermal device or a special-purpose atomiser e.g. a heated quartz cell). Nowadays, commercially available equipment in AFS is simple and compact, specifically configured for particular applications e.g. determination of mercury, arsenic, selenium, tellurium, antimony and bismuth). Therefore, particular details about the components of the instrumentation used in AFS will not be given in this chapter. 

The amorphous forms of selenium do not have specific melting points. Instead, they gradually become softer as they are heated. They may also change from one color and texture to another. 

Both SnSe and SnSea are semiconductors with specific resistances in the range lOi to 10 i ohm cm, but electrical properties vary considerably with the history of heat treatment of the alloys. Impurities in SnSe behave somewhat unusually, and it is likely that antimony for example replaces tin atoms in the lattice up to 200°C, but above that replaces selenium in the lattice . ... 

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