Metal sulphides thermodynamic properties

The choice of topics is largely governed by the author s interests. Following a brief introduction the crystal field model is described non-mathematically in chapter 2. This treatment is extended to chapter 3, which outlines the theory of crystal field spectra of transition elements. Chapter 4 describes the information that can be obtained from measurements of absorption spectra of minerals, and chapter 5 describes the electronic spectra of suites of common, rock-forming silicates. The crystal chemistry of transition metal compounds and minerals is reviewed in chapter 6, while chapter 7 discusses thermodynamic properties of minerals using data derived from the spectra in chapter 5. Applications of crystal field theory to the distribution of transition elements in the crust are described in chapter 8, and properties of the mantle are considered in chapter 9. The final chapter is devoted to a brief outline of the molecular orbital theory, which is used to interpret some aspects of the sulphide mineralogy of transition elements. 

A method for the generation of variable and accurately determined partial pressures of sulphur has been described. The technique enables the study of the thermodynamic and electrical properties of metal-sulphur systems at high temperatures to be carried out and has application to studies of phase diagrams, non-stoicheiometry, electrical conductivity, and of the Seebeck effect. The precision of the stability of the sulphur pressures obtained is controlled by direct determination at high temperatures, using a manganese sulphide probe. 

However, a major limitation to this procedure follows from the reductive properties of syngas, which can lead to the formation of metals, with consequential loss of sorption capacity and metal evaporation further problems can arise from the substantial presence of H2O in the cases of steam gasification, resulting in thermodynamic equilibrium constraints to the reduction of hydrogen sulphide in the gaseous phase below the threshold limits for utilities and downstream process applications. 

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