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Sulphides formation

Peter LM, Wright GA (1987) Electrochemical kinetics of bismuth sulphide formation on bismuth amalgam. Electrochim Acta 32 1353-1356... [Pg.149]

This deposit is located in the north-east of Russia and belongs to a gold-arsenic type of low-sulphide formation (Abramson et al, 1980). It lies within a carbonaceous terrigenous rock of Triassic age and is associated with a dome-shaped uplift in a node of intersecting faults of various directions. The ore bodies consist of zones of silicification and kaolinization with veinlet-disseminated sulphide mineralisation. Gold is present in the form of finely-dispersed dissemination in arsenopyrite and pyrite. As an example. Figure 1 illustrates the distribution of Au and Mn in connection with commercial ore... [Pg.103]

Dos Santos Alfonso and Stumm (1992) suggested that the rate of reductive dissolution by H2S of the common oxides is a function of the formation rate of the two surface complexes =FeS and =FeSH. The rate (10 mol m min ) followed the order lepidocrocite (20) > magnetite (14) > goethite (5.2) > hematite (1.1), and except for magnetite, it was linearly related to free energy, AG, of the reduction reactions of these oxides (see eq. 9.24). A factor of 75 was found for the reductive dissolution by H2S and Fe sulphide formation between ferrihydrite and goethite which could only be explained to a small extent by the difference in specific surface area (Pyzik Sommer, 1981). [Pg.341]

Thioacetamide (H3C.C(S)NH2) has also been commonly nsed in CD. It has the advantage, compared with thionrea, that it works in both acid and alkaline so-Intion. A general decomposition reaction for sulphide formation is... [Pg.47]

Reaction (2.12) occnrs because K p for CdS (10 Table 1.1) is much smaller than that for Cd(OH)2 (2 X 10 ). Another way of looking at this is that the free energy of formation of CdS is more negative than that of Cd(OH)2. It has also been suggested that the hydroxide cluster can act as a catalyst for thiourea decomposition. In this case, sulphide formation will occur preferentially at the surface of the hydroxide rather than nucleate separately in the solution. Such a course is logical based on the previous discussion of the effect of metal cations on the equilibrium of thiourea decomposition. [Pg.50]

At intermediate pH values, particularly in weakly acidic solutions (pH > 2), metal sulphide formation using thioacetamide may proceed through decomposition of a metal ion (or solid phase)-thioacetamide complex rather than through intermediate formation of sulphide [4] (see Sec. 3.3.3). Thioacetamide in pure water is fairly stable and does not readily hydrolyze at room temperature. [Pg.102]

Unfortunately, it is nontrivial to distinguish reliably between the complex-decomposition and sulphide-formation mechanisms. For example, in the study of PbS (as a precipitate) formation from thiourea [47], the two main results used to support complex decomposition were (a) very little sulphide was formed in alkaline solutions of thiourea and (b) addition of PbS powder catalyzed the reaction, seen by the disappearance of the induction time for precipitation and more rapid PbS formation when PbS was added at the start of the reaction. However, these results would also be obtained in a free-anion mechanism, for the following reasons ... [Pg.123]

Thermodynamic analyses of metal sulphide formation from thiosulphate [52] and thiourea [53] and metal selenide formation from selenosulphate [13,54]... [Pg.125]

This is used as a solvent for the percutaneous administration of certain drugs in die horse. It imparts an odour of rotten cabbage, probably as the result of sulphide formation. [Pg.99]

Reid and Schey studied the role of substrate composition and other factors in the formation and performance of films on various metal substrates, including copper, aluminium, titanium and mild steel, tested against themselves and against an alloy steel. They used a twist-compression test to assess performance, and concluded that substrate hardness and composition had the greatest influence on film formation and life. They believed that film formation and especially durability are improved by chemical reaction if a substrate, such as copper or iron, has a strong tendency to react to form a sulphide, provided that the reaction kinetics are favourable. However, they found no direct evidence of reaction or of sulphide formation. Their conclusions were based on the fact that the durability of the films was found to be in the sequence aluminium, titanium, iron, copper, which is the same as the order of the free energies of formation of their sulphides. [Pg.74]

Rickard D. T. (1969) The chemistry of iron sulphide formation at low temperatures. Stockholm Contributions in Geology 20, 67-95. [Pg.3750]

This compound forms acicular crystals or small prisms with melting point 110° C. A detection reaction for the primary arsines is based on this sulphide formation (see p. 328). [Pg.278]

Kovalev, V.A. and Generalova, V.A., 1974. Modeling of sulphide formation from iron humate complexes (in Russian). Geokhimiya, 3 425—533. [Pg.363]

Another variant of initiation by naphthalenide was proposed by Sigwalt (12), who studied the anionic polymerization of propylene sulphide. Formation of propylene in the course of this reaction led him to a following mechanism ... [Pg.430]

Iron aluminides containing 5 wt% Cr, 0.2 wt% Zr and 8 to 16 wt% Al show better resistance to a mixed-gas, H2/1.5 %H2S/4.2%H20 environment at 700°C than conventional A1203- and Cr203-forming alloys, with the extent of sulphide formation for the aluminides increasing with decreasing aluminium concentration in the substrate. [Pg.230]

In principle, the formation of halide scales on metals exposed to halide atmospheres will follow the same mechanisms found to be valid for both oxide and sulphide formation. A comprehensive review of the reactions of metals with halogens has been given by Daniel and Rapp. In fact, many metal halides are almost pure ionic conductors so that the growth of halide scales is expected to be controlled by electron migration rather than by ionic transport. In tbis case, the halide scale will grow laterally over the metal surface more readily than it will thicken. [Pg.169]

In all of the situations shown in Figure 7.5 the principal question is where and under what conditions will the sulphide phase form. It is, therefore, important to define the general conditions for sulphide formation. This will occur whenever the local sulphur activity, or chemical potential, is greater than that required to form sulphide with the metal at the activity that obtains at that site. This condition is stated in Equation (7.21). [Pg.187]

The right hand side of Equation (7.32) corresponds to the triple point A-A , S-A 0 in Figure 7.7. Finally, for a given value of pso2 the value of metal activity required for sulphide formation is given by Equation (7.33a),... [Pg.189]

As can be seen from Equation (7.33b), the critical metal activity required for sulphide formation is proportional to the reciprocal of the SO2 partial pressure. Consequently, at lower values of SO2 partial pressure, the duplex zone will be... [Pg.194]


See other pages where Sulphides formation is mentioned: [Pg.1057]    [Pg.1060]    [Pg.28]    [Pg.124]    [Pg.185]    [Pg.203]    [Pg.415]    [Pg.413]    [Pg.484]    [Pg.8]    [Pg.214]    [Pg.318]    [Pg.237]    [Pg.229]    [Pg.79]    [Pg.314]    [Pg.399]    [Pg.186]    [Pg.187]    [Pg.188]    [Pg.189]    [Pg.191]    [Pg.192]    [Pg.193]    [Pg.193]    [Pg.195]    [Pg.196]    [Pg.197]   
See also in sourсe #XX -- [ Pg.220 ]




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