OXIDE COMPLEXES

Copper III) is known in complex oxides and fluorides and in amino-acid complexes. 

As an indication of the types of infonnation gleaned from all-electron methods, we focus on one recent approach, the FLAPW method. It has been used to detennine the band stmcture and optical properties over a wide energy range for a variety of crystal stmctures and chemical compositions ranging from elementary metals [ ] to complex oxides [M], layered dichalcogenides [, and nanoporous semiconductors The k p fonnulation has also enabled calculation of the complex band stmcture of the A1 (100) surface... 

White phosphorus is very reactive. It has an appreciable vapour pressure at room temperature and inflames in dry air at about 320 K or at even lower temperatures if finely divided. In air at room temperature it emits a faint green light called phosphorescence the reaction occurring is a complex oxidation process, but this happens only at certain partial pressures of oxygen. It is necessary, therefore, to store white phosphorus under water, unlike the less reactive red and black allotropes which do not react with air at room temperature. Both red and black phosphorus burn to form oxides when heated in air, the red form igniting at temperatures exceeding 600 K,... 

Ytterby, a village in Sweden) Discovered by Mosander in 1843. Terbium is a member of the lanthanide or "rare earth" group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Sulfur dioxide concentrations as low as 40 mg/m in air have been determined bypassing air samples through an aqueous solution of tetrachloromercurate, which converts SO2 to the dichlorosulfitomercurate complex. Oxidation of the complex by potassium permanganate is chemiluminescent and the intensity, as measured by a photomultipHer, is proportional to sulfur dioxide concentration (312). 

Benzene-Based Catalyst Technology. The catalyst used for the conversion of ben2ene to maleic anhydride consists of supported vanadium oxide [11099-11-9]. The support is an inert oxide such as kieselguhr, alumina [1344-28-17, or sUica, and is of low surface area (142). Supports with higher surface area adversely affect conversion of benzene to maleic anhydride. The conversion of benzene to maleic anhydride is a less complex oxidation than the conversion of butane, so higher catalyst selectivities are obtained. The vanadium oxide on the surface of the support is often modified with molybdenum oxides. There is approximately 70% vanadium oxide and 30% molybdenum oxide [11098-99-0] in the active phase for these fixed-bed catalysts (143). The molybdenum oxide is thought to form either a soUd solution or compound oxide with the vanadium oxide and result in a more active catalyst (142). 

There are numerous complex (ternary and quaternary) plutonium oxides. Their properties have been reviewed (30). Plutonium oxidizes readily to Pu(VI) from binary oxides to complex oxides such as Ba PuO. The best way to oxidize Pu to Pu(VII) is to prepare complex oxides such as Li PuO from Li20 and PUO2 iu flowing oxygen (85). 

Thin films of photochromic silver complex oxides were prepared by anodic oxidation of silver metal films (15). Complex oxides, such as Ag2V04, Ag SiO, and Ag2P04, darkened by exposure to visible light, but required heating to 150—250°C for thermal bleaching. 

Pigment Systems. Most of the crystals used for ceramic pigments are complex oxides, owing to the great stability of oxides in molten silicate glasses. Table 3 fists these materials. The one significant exception to the use of oxides is the family of cadmium sulfoselenide red pigments. This family is used because the colors obtained caimot be obtained in oxide systems thus it is necessary to sustain the difficulties of a nonoxide system. 

The cycle shown in Figure 20.4 at first appears to be a complicated way to oxidize acetate units to COg, but there is a chemical basis for the apparent complexity. Oxidation of an acetyl group to a pair of COg molecules requires C—C cleavage ... 

F. Wells, Structural Inorganic Chemistry, 5th edn., Oxford University Press, Oxford, 1984 Chap. 12, Binary metal oxides, pp. 531-74 Chap. 13, Complex. oxides, pp. 575-625. 

The modes of thermal decomposition of the halates and their complex oxidation-reduction chemistry reflect the interplay of both thermodynamic and kinetic factors. On the one hand, thermodynamically feasible reactions may be sluggish, whilst, on the other, traces of catalyst may radically alter the course of the reaction. In general, for a given cation, thermal stability decreases in the sequence iodate > chlorate > bromate, but the mode and ease of decomposition can be substantially modified. For example, alkali metal chlorates decompose by disproportionation when fused ... 

The hot rolling of steel produces a surface layer of complex oxides known as millscale . It is unstable, losing adhesion upon weathering, and must be removed prior to painting if predictable paint performance is to be obtained. 

Tantalum and niobium are added, in the form of carbides, to cemented carbide compositions used in the production of cutting tools. Pure oxides are widely used in the optical industiy as additives and deposits, and in organic synthesis processes as catalysts and promoters [12, 13]. Binary and more complex oxide compounds based on tantalum and niobium form a huge family of ferroelectric materials that have high Curie temperatures, high dielectric permittivity, and piezoelectric, pyroelectric and non-linear optical properties [14-17]. Compounds of this class are used in the production of energy transformers, quantum electronics, piezoelectrics, acoustics, and so on. Two of... 

The hydrofluoride method can be used successfully both for the preparation of complex fluoride compounds and of complex oxides. The main advantage is that the synthesis is performed at relatively lower temperatures. In addition, the complex oxide material is formed through its respective fluoride compound and the product obtained is therefore more consistent. For instance, Co4Nb209 can be prepared using the hydrofluoride method at 900-1100°C, whereas the regular synthesis, based on the interaction of simple oxides, requires extended treatment at about 1400°C. 

The processing of tantalum and niobium begins with the fluorination of the raw material, which always consists of complex oxide compounds containing tantalum and niobium. The main types of tantalum- and niobium-containing minerals are discussed in Chapter 1, and typical compositions of such minerals are presented in Table 2. 

In both cases, the fluorination of the complex oxides of tantalum and niobium leads to the formation of the water-soluble compounds (NH4)2TaF7 and (NH4)3NbOF6, the insoluble lithium fluoride and die gaseous components H20, NH3 and HF. 

Since the fluorination enables to separate components of complex oxide compounds containing tantalum and niobium, it seems that it is applicable for... 

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