Sulphides, metal

Preparation of Metal Sulphides from the Elements. Perform the experiment in a fume cupboard ) Copper Sulphide. Fill one-third of a test tube with sulphur and heat it up to boiling. The sulphur vapour should fill the entire tube. Hold a piece of copper gauze or foil with pincers, heat it in the flame of a burner until red hot, and rapidly introduce it into the sulphur vapour. What happens Write the equation of the reaction. How does copper snlphide react with water and hydrochloric acid  

Throw a small amount of aluminium sulphide into a test tube with hot water. Explain what occurs. Write the equations of the reactions. 

Iron Sulphide. Prepare 5 g of a mixture of sulphur and a powder of reduced iron taken in equivalent amounts, transfer it into a test tube, secure the latter in the clamp of a stand, and heat the bottom of the tube on a strong flame until a reaction begins. As soon as this occurs, remove the burner. What is observed Write the equation of the reaction. How can you prove that the compound obtained is a sulphide Test the reaction of iron sulphide with hydrochloric acid. 

Zinc Sulphide. Using equivalent amounts of zinc (a powder) and sulphur, prepare about 5 g of a mixture, put it on a metal plate, and heat it carefully, in a fume cupboard ). What occurs Write the equation of the reaction. See how zinc sulphide interacts with water and hydrochloric acid. 

Preparation of Metal Sulphides by an Exchange Decomposition Reaction. Precipitation with Ammonium Sulphide. Pour 2 ml each of solutions of iron(ll), manganese(II), zinc, cadmium, lead, antimony, and copper salts into separate test tubes. Add 2 ml of an ammonium sulphide solution to each tube. Note the colour of the formed precipitates. Write the equations of the reactions and the values of the solubility products of the sulphides of these metals (see Appendix 1, Table 12). Using the concept of the solubility product, explain the process of precipitation of sulphides under these conditions. 

Aluminium Sulphide. Weigh 1 g of aluminium powder and the calculated amount of finely triturated sulphur, and thoroughly mix the reactants. Spill out the mixture in a mound onto a metal plate and put a magnesium ribbon in the middle so that its upper end protrudes 1-2 cm above the mixture. Ignite the magnesium in a fume cupboard with a lowered glass window ). How can you explain the hydrogen sulphide odour of the aluminium sulphide  

Electronic properties of the disulphides of the fourth, fifth and sixth group transiton metals crystallizing in the Cdl2(lT), MoS2(2H, 3R) and related polytypic structures have been rationalized by similar considerations. Covalent interaction between quadrivalent cations and sulphide ions is so strong that collective d states are formed in all the cases. The properties crucially depend on the electronic configuration and the 

The trisulphides (and triselenides) of Ti, Zr, Hf, Nb and Ta crystallize in onedimensional structures formed by MSg trigonal prisms that share opposite faces. Metal atoms in these sulphides are formally in the quadrivalent state, and part of the sulphur exists as molecular anions, M S2 S . TaSj shows a metal-insulator transition of the Peierls type at low temperatures (Section 4.9). NbSj adopts a Peierls distorted insulating structure suggesting the possibility of a transformation to a metallic phase at high temperatures, but does not transform completely to the undistorted structure. Electronic properties and structural transitions of these sulphides have been reviewed (Rouxel et al, 1982 Meerschaut, 1982 Rouxel, 1992). 

A large number of binary metal-rich sulphides (S/M ratio 1.0) possessing metal-metal bonds are known (Franzen, 1978). Typical of them are V3S, V5S4, ZrjS, HfjS, T a S and Nbj 1 Sg. Stoichiometry of such solids cannot be understood in terms of the traditional concepts of valence, owing to the presence of extensive metal-metal bonding. 

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Sulphur dioxide, SO2, m.p. — 72-7°C, b.p. — I0"C. Colourless gas with characteristic smell. Formed by burning S, metal sulphides, H2S in air or acid on a sulphite or hydrogen sulphite. Powerful reducing agent, particularly in water. Dissolves in water to give a gas hydrate the solution behaves as an acid - see sulphurous acid. Used in the production of SO3 for sulphuric acid. 

Gases which are high in FIjS are subject to a de-sulphurisation process in which H2S is converted into elemental sulphur or a metal sulphide. There are a number of processes based on absorption in contactors, adsorption (to a surface) in molecular sieves or chemical reaction (e.g. with zinc oxide). 

Selenium and tellurium occur naturally in sulphide ores, usually as an impurity in the sulphide of a heavy metal. They are recovered from the flue dust produced when the heavy metal sulphide is roasted. 

Sulphur can be reduced directly to hydrogen sulphide by passing hydrogen through molten sulphur the reversible reaction H2 -I-S H2S occurs. In the laboratory the gas is most conveniently prepared by the action of an acid on a metal sulphide, iron(II) and dilute hydrochloric acid commonly being used ... 

Since most metallic sulphides are insoluble, many are precipitated when hydrogen sulphide is passed through solutions containing ions of the metals. Some are precipitated in acid, and others in alkaline... 

Hydrogen sulphide is used in the preparation of metal sulphides, oil additives ete., in the purifieation and separation of metals, as an analytieal reagent and as raw material in organie synthesis. It burns in air with a blue flame ... 

Hydrogen sulphide oeeurs naturally, e.g. in natural gas and petroleum, voleanie gases, and from deeaying organie matter. It may be present near oil wells and where petroleum is proeessed. Commereially it is obtained as a by-produet from many ehemieal reaetions ineluding off-gas in the produetion of some synthetie polymers (e.g. rayon, nylon) from petroleum produets, and by the aetion of dilute mineral aeids on metal sulphides. Physieal properties are summarized in Table 9.14 and effeets of temperature on vapour pressure are shown in Figure 9.5. 

Patches of conductive lead sulphide can be formed on lead in the presence of sewage. This can result in the flow of a large corrosion current . Sulphate-reducing bacteria in soils can produce metal sulphides and H2S, which results in the formation of deep pits containing a black mass of lead sulphide . Other micro-organisms may also be involved in the corrosion of lead in soil . 

Crucibles fitted with permanent porous plates are cleaned by shaking out as much of the solid as possible, and then dissolving out the remainder of the solid with a suitable solvent. A hot 0.1 M solution of the tetrasodium salt of the ethylenediaminetetra-acetic acid is an excellent solvent for many of the precipitates [except metallic sulphides and hexacyanoferrates(III)] encountered in analysis. These include barium sulphate, calcium oxalate, calcium phosphate, calcium oxide, lead carbonate, lead iodate, lead oxalate, and ammonium magnesium phosphate. The crucible may either be completely immersed in the hot reagent or the latter may be drawn by suction through the crucible. 

The dispersion (or sols) are only slightly viscous. Examples sols of metals, silver halides, metallic sulphides, etc. 

With the aid of a table of solubility products of metallic sulphides, we can calculate whether certain sulphides will precipitate under any given conditions of acidity and also the concentration of the metallic ions remaining in solution. Precipitation of a metallic sulphide MS will occur when [M2 + ] x [S2 ] exceeds the solubility product, and the concentration of metallic ions remaining in the solution may be calculated from the equation ... 

It must be pointed out that the above calculation is approximate only, and may be regarded merely as an illustration of the principles involved in considering the precipitation of sulphides under various experimental conditions the solubility products of most metallic sulphides are not known with any great accuracy. It is by no means certain that the sulphide ion S 2 is the most important reactant in acidified solutions it may well be that in many cases the active precipitant is the hydrogensulphide ion HS , the concentration of which is considerable, and that intermediate products are formed. Also much co-precipitation and post-precipitation occur in sulphide precipitations unless the experimental conditions are rigorously controlled. 

Kinetic observations for decomposition of some representative transition metal sulphides are summarized in Table 13. Several instances of an advancing interface [contracting volume, eqn. (7), n = 3] rate process have been identified and the rate may be diminished by the presence of sulphur. Diffusion control is, however, believed to be important in the reactions of two lower sulphides (Ni0.9sS. [687] and Cu1-8S [688]). These solids have attracted particular interest since both are commercially valuable ores and pyrolysis constitutes one possible initial step in metal extraction. 

Summary of kinetic characteristics for decompositions of some transition metal sulphides... 

The application of ly transition metal carbides as effective substitutes for the more expensive noble metals in a variety of reactions has hem demonstrated in several studies [ 1 -2]. Conventional pr aration route via high temperature (>1200K) oxide carburization using methane is, however, poorly understood. This study deals with the synthesis of supported tungsten carbide nanoparticles via the relatively low-tempoatine propane carburization of the precursor metal sulphide, hi order to optimize the carbide catalyst propertira at the molecular level, we have undertaken a detailed examination of hotii solid-state carburization conditions and gas phase kinetics so as to understand the connectivity between plmse kinetic parametera and catalytically-important intrinsic attributes of the nanoparticle catalyst system. 

Carburization was carried out in a fixed-b i stainlras strel reactor (ID = 6 mm). Typically about 0.5 g of metal sulphide was sandwiched between 2 layers of quartz wool placed centrally in a temperature-programmed furnace. iTie sample was heated at 10 Kmin" to the... 

Tacconi NR, Medvedko O, Rajeshwar K (1994) Cathodic electrosynthesis of metal sulphide thin films at a sulphur-modified gold surface application to the iron sulphide system. 1 Electroanal Chem 379 545-547... 

Atiwi SM, Al-Jubori KE (1989) Photoreduction of CO2 by metal sulphide semiconductors. Sol Energy Mater 18 223-229... 

Sulphur/metal mixtures form metal sulphides. The reaction can be very violent. This is the case for lithium or magnesium when both the metal and sulphur are in the molten state. This is also true for sodium by heating. The reaction is much less violent when sodium chloride is present. It is also less dangerous if the interaction is made in toluene. 

Calcium chlorate reacts dangerously as do metal chlorates. This occurs with interactions of this compound with carbon, aluminium, metal sulphides, sulphur and phosphorus. 

Sulphur, hydrogen sulphide and metal sulphides also led either to the ignition of the sulphurous substance (S and H2S) or the incandescence of the mixture. Note that sulphides and cyanides are amongst the most dangerous salts in the presence of oxidants, a fact not to be ignored. 

Electrodes containing a mixture of divalent metal sulphides and Ag2S are used to determine Pb2+, Cu2+ and Cd2+. 

Mills AM, Ruck M (2005) Ce53Fe12S9oX3 (X = Cl, Br, I) The first rare-earth transition-metal sulphide halides. Inorg Chem 45 5172-5178... 

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