Pure Sulphur Research Articles

Properties of fused polysulphides—VII. The phase diagram Li 2S/Na 2S/S

The phase diagram of the system Li 2S/Na 2S/S has been investigated at 400°C. In the sulphur-rich part of the ternary diagram, two liquid phases exist; one of these is nearly pure liquid sulphur, and the other is an alkali metal polysulphide melt. When sulphur is removed, the polysulphide remains as a single liquid phase. The composition limits of the two-liquid region have been determined by equilibrating the two liquid phases, quenching the analysing. If more sulphur is removed from the polysulphide melt, solid phases eventually separate. The composition boundary the polysulphide liquid and the (one liquid, one solid) region of the diagram has been determined, by separating the phases using high temparature centrifuge and subsequent analysis. For all Li/Na ratios between 100/0 and 20/80, the solid phase separating is Li 2S; in the pure sodium system, it is Na 2S 2. No evidence was found for solid lithium polysulphides or for solid phases containing both sodium and lithium. The significance of this diagram with respect to the properties of a hypothetical (sodium,lithium)-sulphur cell is discussed.

Spectrophotometric determination of bituminous impurities in raw Frasch sulphur

Both bitumen and pure sulphur absorb in the visible region of the electromagnetic spectrum at about 395 nm, when measured in CS 2 solution. However, the extinction coefficient of bitumen (9.36 lg −1cm −1) is 160 times greater than that of sulphur (5.80 × 10 −2 lg −1cm −1). This has allowed a method of acceptable accuracy to be established, to determine the amount of bitumen in sulphur. This method is based on the relationship between increased total area of the absorption band, and quantities of bitumen added to the pure sulphur sample.

Elemental sulphur formation during the ferric chloride leaching of chalcopyrite

The formation of elemental sulphur during the FeCl 3 leaching of chalcopyrite has been elucidated. More than 95% S° formation, and less than 5% SO 4 generation, is observed regardless of the leaching time (0–90 h), the FeCl 3 concentration (0–2 M), the HCl concentration (0–3 M) and the chalcopyrite particle size. Furthermore, the relative amounts of S° and SO 4 do not vary systematically with any of the above variables. Surprising is the observation that the presence of air or O 2 in the leach reactor has no significant effect on the relative amounts of S° and SO 4, and this observation was confirmed in separate leaching tests with pure sulphur. The morphology of the elemental sulphur reaction product also was ascertained. Although discrete globules of S° form on large chalcopyrite particles, smaller chalcopyrite grains (<20 μm) become completely enveloped in a continuous layer of sulphur within the first 15 min of leaching. The morphology of the sulphur does not change with the concentration of either FeCl 3 or HCl.

Vapour—liquid equilibrium in the sulphur hexafluoride — n-pentane system at high pressure

Vapour pressure of pure sulphur hexafluoride was measured in the temperature range from 290 K to the critical point. Measurements of binary vapour—liquid equilibrium data were carried out isothermally at temperatures 313.15 K, 323.15 K, and 333.15 K and pressures from 2 MPA up to near the critical pressure (4 MPa maximum). A part of the vapour—liquid critical line was determined for mole fraction of sulphur hexafluoride higher than 0.7, which means the temperature range from 319 to 340 K and the pressure range from 3.7 to 4.2 MPa.

X-ray emission spectroscopy study of substoichiometric Bi 2 − xSb xS 3 system

A definite chemical shift has been observed for S Kα 1 − 2 in Bi 2S 3, Sb 2S 3 and other Bi 2 − xSb xSe 3 compounds. The result shows that the emission spectrum of pure sulphur consists of three bands around 2307, 2321 and 2289.6 eV whereas those of the compounds of sulphur show bands around 2305 and 2321 eV only. The S Kα 1 − 2 peak shifts to the low energy side in all the compounds studied here. The shape of the S Kα peak in the compounds is found to be highly assymetric in nature. On the basis of the shift Δ E in the S Kα peak, the charge associated with the sulphur atom has been calculated.

Correlation between tips in scanning tunneling microscope and image obtained

Starting from pure metals and sulphur in evacuated silica tubes single crystals of Cu5.47(9)Fe2.9(3)Sn13.1(3)S32 have been obtained by quenching from 680°C. It crystallizes in the Fd3m space group with a = 10.3022 (6) Å. The atomic parameters, occupancies, and anisotropic thermal parameters were refined to give a final R-value of 0.0116. The 119Sn Mössbauer study shows the presence of Sn (IV) in an octahedral environment and 57Fe Mössbauer indicates the presence of Fe (II) in an octahedral environment, statistically distributed in both low- and high-spin configurations.

Hydrogen Neutralization of Chalcogen double donor Centers in Single-Crystal Silicon

ABSTRACTChalcogen (S,Se,Te) -doped silicon samples were hydrogen neutralized by different passivation techniques. The electrically active double-donor densities were determined by DLTS measurements. DLTS spectra reveal that both donor levels recover simultaneously. The activation energy for re-activation of neutralized isolated and pure pair sulphur double-donors is Ea(So/+) = 2,13 ± 0,15 eV and Ea(S2o/+) = 2,1 ± 0,15 eV, respectively.

Grain boundary penetration of liquid sulphides in nickel, cobalt, and iron

The attack on pure nickel, cobalt, and iron in the presence of pure sulphur vapours has been studied in the temperature range between 700 and 1150°C. The formation of liquid sulphides which penetrate along the grain boundaries of the solid metals has been detected. The dihedral angles have been measured as a function of temperature, and the temperature dependence of grain boundary andSolidi/liquid interfacial tensions have been computed. The kinetics of penetration of the liquid phase along the grain boundaries have been established and interpreted using Mullins'analysis.MST/248

Grain boundary penetration of liquid sulphides in nickel, cobalt, and iron

AbstractThe attack on pure nickel, cobalt, and iron in the presence of pure sulphur vapours has been studied in the temperature range between 700 and 1150°C. The formation of liquid sulphides which penetrate along the grain boundaries of the solid metals has been detected. The dihedral angles have been measured as a function of temperature, and the temperature dependence of grain boundary andSolidi/liquid interfacial tensions have been computed. The kinetics of penetration of the liquid phase along the grain boundaries have been established and interpreted using Mullins'analysis.MST/248

活性硫黄末によるアンモニア性銅溶液中の銅の除去

Activated sulphur prepared by means of sulphidizing suspension electrolysis contains a few percent of CuS which covers uniformly the surface of sulphur particles. The sulphur is placed and agitated in ammonia-alkaline solutions (pH 9-11) containing 0-2 mol/dm3 NH4Cl and 1-10g/dm3 Cu as the Cu-NH3 complex. Precipitation of CuS then takes place at the sulphur surface by the disproportionation reaction catalyzed by the CuS layer. The residual concentration of copper is reduced to 1 ppm or less after 1-30 hrs at 20-40°C. The rate increases when the pH and temperature are high, or the free NH3 concentration is low.In contrast to these results, the copper concentration in suspension of pure sulphur decreases only 35 ppm after 16 days at pH 10 and room temperature.The reaction rate is represented by the logarithmic rate law as given by.1-C/C0=βlog (kt/β+1)where C0 and C are the concentration of Cu at the initial and at a time t, respectively, k and β are rate constants. The effects of pH, NH3 and NH4+ concentrations, temperature, C0, and slurry density of sulphur on the rate constantsare investigated. It is found that β(0.8-2.2) is rather irrelevant to the experimental conditions, whereas k varies in a wide range from 0.1-10 h-1. The activation energy of the reaction is 143 kJ/mol.The reaction mechanism has been discussed that the disproportionation reaction is to be a combination of a cathodic reaction to. deposit CuS and an anodic reaction where sulphur is oxidized to supply electrons which are necessary to promote the cathodic reaction. It seems that the anodic reaction is the rate controlling step and the CuS layer on the sulphur surface plays a role both for acceleration of the anodic reaction rate and rapid transfer of electrons.

Hydration of the surface of pure sulphur covered with n-alkanes

This paper presents the results of an investigation of the kinetics of adsorption and desorption of water on the surface of pure sulphur covered with n-alkanes. Changes of thermodynamic functions depending on adsorption values, as well as activation energy of water molecules were determined. On the basis of these results the effect of n-alkanes on the thickness of water layers formed on modified sulphur samples was shown. The mechanism of water adsorption here gives much information on the mode of molecule bonding on the sulphur surface.

Attachment, detachment and ion-molecule reactions in SO2 and SO2-O2 mixtures

A pulsed drift tube has been employed for measurement of the electron attachment coefficient, alpha a in pure sulphur dioxide over the E/N range 3.03<or=E/N<or=242.4 Td. A pressure dependence of alpha a/(SO2) has been observed for E/N<40.0 Td, indicating the existence of a three-body attachment process, whilst for values of E/N>40 Td the results indicate a dissociative attachment process. Measurements of the mobility of the negative ions formed indicate the presence of at least four ions with reduced mobilities of 0.69, 0.62, 0.55 and 0.39 cm2 V-1 s-1 respectively. Using a drift tube mass spectrometer system the ion spectra produced in pure SO2 and in SO2-O2 mixtures have been studied. In pure SO2 at pressures around 1 Torr a number of large cluster ions are observed. At much lower pressures the predominant ion is SO2- which rapidly clusters to form SO2.SO2- as the pressure increases. When SO2 is added to oxygen the following reactions are observed: O-+SO2 to SO3+e; O2-+SO2 to SO2-+O2. The rate for the first reaction has been measured over a range of E/N and has been found to vary between 2.0*10-9 cm3 s-1 and 8*10-10 cm3 s-1. The second reaction has a rate of 3.9*10-9 cm3 s-1 at E/N=117.2 Td.

Crystallization of silicon from the silicon-chalcogen vapor phase

With the target of preparing homogeneous chalcogen-doped silicon crystals, conditions and features of vapor phase growth have been investigated. Consequent evaluation of this work, for the first time, demonstrated how to grow S-doped crystals in such manner, and principally, enabled us to guide transport reactions via the pure sulphur, selenium, and tellurium system, respectively, in order to obtain large and highly perfect crystal areas. Optimization of the “sandwich method” which is known from the literature as a close-spaced system allowed us to realize epitaxial growth layers of thicknesses up to 10 mm based on diameters of 30 mm maximum.

The dispersion of powders by intense electrostatic fields. I. Experimental studies

Powder dispersion by electrostatic fields above 0.20 kV/mm has been studied at ambient temperature in a vacuum, air, sulphur dioxide, and insulating liquids, with both conducting and nonconducting powders. All the conducting powders examined were dispersible, but only some of the insulating materials (e.g., alumina) reacted to the field. Alumina was studied in some detail using different media and various electrode geometries. It was concluded that dispersion of insulating powders occurs as a result of a conducting surface film, indicating that charging of the particles is mostly by conduction electrons from the bed. Effects of the dispersing medium were also detected, especially through the use of current-voltage curves. When liquids were used instead of air, for example, pronounced hysteresis occurred, an effect ascribed to the increased settling rate of the particles. Differences in behavior were also demonstrated from one gaseous medium to another, e.g., particulate clouds, which normally show pronounced turbulence in high-voltage air dispersion, became much more uniform in pure sulphur dioxide. In addition, some powders such as lycopodium, which is unreactive to the field in air, dispersed well in sulphur dioxide. This was traced back to the corona-suppressing properties of this gas, demonstrating that production of gaseous ions at field concentrations (such as those produced by sharp electrodes or angular particles) is detrimental to electrodispersion, since ions tend to act as charge carriers in preference to the particles. Further evidence of this came from gamma ray attenuation studies used for measuring cloud densities as a function of the applied field.

The electrical conductivity of liquid sulphur

Abstract The electrical conductivity [sgrave] of very pure liquid sulphur has been measured between 300 and 900°C at pressures slightly above the vapour pressure. A comparison of the results with recent optical absorption and E.S.R. measurements leads to the conclusion that the free-radical chain-ends in liquid sulphur give rise to carriers which determine [sgrave] at high temperatures. The effect of a small concentration of impurities on [sgrave] is discussed.

Investigation of the Effect Produced by Short-range and Long-range Order on the Spectrum of Valence Electrons in Solids

X-ray photoelectron spectra of valence and core electrons are obtained for AgI, Ag2S, Ag2Se, Ag2Te, Ag2HgI4, Cu2HgI4 and Cu2S–compounds which reveal a lattice instability at temperature increase. X-ray photoelectron spectra of valence and core electrons in the chalkogenides AgAsS2, AgSbS2, and AsGeS in crystalline and glass-like states were studied. For AsGeS in crystalline and glass-like state the X-ray emission LII,III-spectra of sulphur were investigated. K- and LII,III-emission spectra of pure sulphur were also obtained. When the compounds go from the crystalline state into the α-phase, a smoothing takes place of structural singularities in the photoelectron spectra in the region of energy localization of the states of the non-metallic components. The structural singularities are clearly resolved in the X-ray photoelectron spectra of AgAsS2 and AgSbS2 crystals but are smoothed in the spectra of the glass-like state. The X-ray photoelectron spectrum of the glass-like state has two maxima near the valence band top while the spectrum of the crystal has only one maximum. For AsGeS in its glass-like state the singularities of the fine structure observed in the LII,III-emission spectrum of sulphur are less pronounced than in the corresponding spectrum of the crystalline state. When the investigated compounds of Ag and Cu go from the crystalline state into the α-phase and when the chalcogenides AgAsS2, AgSbS2, and AsGeS are transferred from the crystalline into the glass-like state the atom charge state does not undergo perceptible changes. The alterations observed in the X-ray photoelectron spectra when compounds transfer from a crystalline state into one with a lattice instability or into a glass-like state are due to the effect produced on the energy structure of valence electrons by the short- and long-range order in the arrangement of atoms of metal and nonmetal components in the compound.

The reaction of titanium with sulphur vapour

The kinetics of reaction of coupons of annealed and unannealed titanium with pure sulphur vapour have been investigated by a thermogravimetric method over the temperature range 450–550 °C. The sulphurization kinetics for the annealed metal were parabolic and for the unannealed titanium they were pseudo-parabolic. The apparent activation energy calculated from the parabolic rate constants was 27 kcal mol −1. For the annealed metal parabolic kinetics were observed for total sulphur pressures in the range 0.2–300 Torr; the parabolic rate constant increased as the square root of the partial pressure of S 2. The only reaction product detected under all experimental conditions was Ti 1 + x S 2, which microprobe analysis showed to be slightly metal-rich. For a given temperature and sulphur pressure the sulphurization rate was independent of the presence of inert gas or hydrogen but was strongly and erratically influenced by the presence of oxygen. The sulphurization process is discussed in terms of a reaction controlled by the diffusion of titanium through the thickening Ti 1 + x S 2 scale.

Preparation of very pure sulphur. (Czechoslovakia): P Bor, Chem Listy, 69 (3), 1975, 276–280 ( in Czech)

Preparation of very pure sulphur. (Czechoslovakia): P Bor, Chem Listy, 69 (3), 1975, 276–280 ( in Czech)

The Application of SF6 in the Geochemical Research

For mass spectrometric measurements of δ31S, pure sulphur hexafluoride was prepared quantitatively from different mineral sulphides by the reaction with elemental fluorine under pressure. The results of δ31S measurements on SF6 samples were confirmed by comparison of δ31S values with the classical method leading to SO2. Numerous mass spectrometric measurements of SF6 and SO2 with regard to the experimental conditions of the synthesis, the influence of background, memory effect, and adsorption were made. The measurements of small isotopic variations of sulphur with SF6 has advantages in comparison to the SO2 technique. The method described can be successfully used for routine work.

The reaction of tungsten with sulphur vapour

A thermogravimetric method has been used to investigate the kinetics of the reaction of both annealed and unannealed tungsten coupons with pure sulphur vapour at temperatures between 295 and 550 °C. The rates of sulphurization of both forms of metal were rapid and increased systematically with temperature to a rate maximum at 460–475 °C; thereafter the rates decreased. At temperatures below the rate maximum, the apparent activation energies were in the range 31–34 kcal/mole. For the annealed metal, the kinetics were essentially linear. The kinetics of sulphurization of the unannealed metal were linear above the rate maximum but, below this transition temperature, the reaction rate increased with time. For both forms of metal, the initial sulphurization rates increased in a complex manner with increasing sulphur pressure for temperatures below the rate maximum. Above this transition temperature, the rates increased directly with the partial pressure of S 2. Tungsten disulphide was the only reaction product detected under all experimental conditions.