Sulfides of metals

Silica, the silicates and, in general, crystals containing oxygen or fluorine and metal atoms which can form noble-gas type cations are found to satisfy the electrostatic valence rule and the other rules for ionic crystals, which indicates that the ionic character of these substances is of greatest importance. The sulfides of metals other than the alkalies and alkaline earths, on the other hand, do not satisfy these rules magnetic evidence further shows these substances not to be ionic. 

Only a limited amount of thermodynamic data are available for 2-D sulfides of metals other than nickel. Data reported for Ag (57), Co (252), Cu (255), Fe (252, 154), Mo (255, 255), Ru (256), and Pt (84, 85) indicate that the heats of sulfur adsorption are generally 20-40% larger than the heats of formation of the most stable bulk sulfides. Indeed, Benard et al. (255) have shown a linear correlation between the heats of adsorption of sulfur and the... 

Ceramic materials can be made from the oxides, nitrides, carbides, or sulfides of metals. The precursor solution must contain both the metal and the requisite O, N, C, or S in close liaison. Three broad... 

Use Purification of hydrochloric acid and sulfuric acid, precipitating sulfides of metals, analytical reagent, source of sulfur and hydrogen. 

Arsenic is ubiquitous in nature and is found in detectable concentrations in all environmental matrices. The occurrence of As in the continental crust of Earth is usually given as 1.5 to 2.0 mg/1. The distribution of arsenic in nature is extremely variable, showing little correlation with geological formation, climate, or soil. Numerous minerals, rocks, sediments and soils contain arsenic partly as constituent of sulfide minerals or complex sulfides of metal cations and partly as a constituent retained by soils and/or sediments in occluded or adsorbed forms. The latter is manifested primarily by the adsorption or occlusion of As on hydrous A1 and Fe oxides, but these are not necessarily the only source. Arsenic is also adsorbed on clay colloid, is bound to organic matter and may form slightly water soluble compounds with Al, Fe, Ca and Mg in the soil matrix. Some of the more common minerals in soils are arsenopyrite (FeAsS), Orpiment (AsgSg) etc. 

Objective 16 61. Hydrogen sulfide, H2S, used to precipitate sulfides of metals, is a colorless gas... 

The most important MX structures involving tetrahedral coordination are the cubic ZnS sphalerite (Fig. 5a) and the hexagonal ZnS wurtzite (Fig. 5b) arrangements. It is striking that halides and sulfides of metal ions with d5 and d10 shells have a tendency to crystallize in the sphalerite structure for example, the cuprous halides, Agl, HgS, MnS, CdS, and ZnS. (The last three also occur in the wurtzite modification, as do the oxides of Zn and Be). (See Table V.) Here again, the simple ionic theory fails to account for the facts for (1) the radius ratios of some of these compounds are compatible with a 6-coordinated structure, and (2) interatomic distances calculated from the usual ionic radii (decreased by 5% to com-... 

Table II. Sulfiding of Metals in Automobile Exhaust Gas Atmosphere, [SO2/H2]0 [H2S/H2]...

Because the sulfides of metals have a lower heat of formation than the oxides, some difficult-to-obtain metals can be made from their lulfides with aluminum. This process has been described by Gardner > for niobium (columbium) and tantalum from their disulfides (NbS and TaSj), whereby the relatively volatile by-product Al S, distills off above 1550°C. It is an interesting coincidence that the production of the same two metals by reduction of the pentoxides NbfOs and Ta s with silicon can be performed under formation of silicon (II) oxide (SiO), which volatilizes in vacuum. 

Oxides and sulfides of metals react with phosgene at elevated temperatures, usually yielding very pure chlorides. The reaction of phosgene with cadmium... 

Hydrogen sulfide is used commercially to purify hydrochloric and sulfiiric acid, to precipitate sulfides of metals, and to manufacture elemental sulfiir and organosulfur compounds. Chemical production processes using hydrogen sulfide include the manufacture of mercaptans pharmaceuticals plastics adhesives television, cathode ray tubes (CRT), and fluorescent tube phosphors dyes pigments biodegradable pesticides ethylene nylon soda ash sodium hydrosulfide heavy water and others. 

Treatment with hydrogen sulfide of metal-ion-exchanged solid acids enhances the acidity and catalytic activity. ... 

Under these conditions, the vapor sulfur molecule is diatomic and the reaction only produced a sulfide of metal M MS. 

Most metals react directly with sulfur to form sulfides, which in the main are very insoluble in water, although the sulfides of metals from Groups I and II are ionic, and are soluble. However, like oxides, they are salts of a weak acid, and are therefore extensively hydrolysed in solution ... 

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