Optical Absorption of Liquid Sulfur under High Pressure. Pressure Dependence of the Polymerisation of Liquid Sulfur

Three different types of two‐phase equilibria have to be considered in fluid mixtures: liquid‐gas, liquid‐liquid, and gas‐gas equilibria. The pressure dependence and critical phenomena of these kinds of phase equilibria will be shortly reviewed and recent data will be presented: since mainly high‐pressure work, say above 300 bar up to several kbar, will be discussed, liquid‐liquid and gas‐gas equilibria in particular will be considered.New developments during recent years have shown that the limits between these three forms of phase equilibrium in fluid mixtures are not well defined at high temperatures and pressures and that continuous transitions between all these types occur. This continuity will be demonstrated for binary mixtures of hydrocarbons with CO2 and H2O.

Phase Behavior and Critical Phenomena in Fluid Mixtures under Pressure

Schneider

1972

Reflection Spectra of Fluid Sulphur in the Sub‐ and Supercritical Region

Tamura

Seyer

Hensel

1986

The dielectric dispersion of fluid sulphur has been investigated, for the first time, by means of normal incident reflectivity measurements in the range 0.5–6.0 eV over the entire liquid vapor range at temperatures between 120°C and 1100°C and at pressures between 20 bar and 500 bar. The optical response functions ε1(ω) and ε2(ω) have been derived from the reflectivity spectra by means of a modified Kramers‐Kronig analysis. The reported measurements give useful information about the electronic structure of fluid sulphur. The polymerization transition (159°C) shifts the first optical absorption towards lower absorption energy by about 0.7 eV. In the supercritical fluid at low densities distinct bands can be observed for S3, S4 and S2. As the density is increased, these bands merge to form the optical edge of the dense fluid.

Optical Absorption Spectra of the Homocyclic Sulfur Molecules S_n (n = 6, 7, 8, 9, 10, 12, 15, 20) in Solution [1]

Steudel

Jensen

Göbel

et al. 1988

The optical absorption spectra of the sulfur homocycles Sn (n = 6–10,12, 15, 20) in methanol or methylcyclohexane solution have been recorded in the region 200–360 nm using a conventional spectrophotometer as well as a diode‐array spectrophotometer. Each compound shows a characteristic absorption curve. The extinction coefficients at 254 nm increase with increasing ring size, and the lowest‐energy absorption maximum shifts to the red with increasing number of atoms in the molecule. The data are used to re‐interprete the published absorption spectra of liquid and irradiated sulfur.