Platinum group metals physical properties

See also Potassium-sodium (NaK) alloys physical properties of, 20 604t Naked license, 25 265 AT-aldehydes, platinum-group metal catalysts and, 19 621 Naled, 4 358t... 

For the overall performance of potential catalysts in practical application additional factors, such as number of active sites, physical form, and porosity must also be taken into account. The classical commercial iron catalyst is an unsupported catalyst. First of all iron is a cheap material and secondly by the incorporation of alumina a surface area similar to that attained in highly dispersed supported catalysts can be obtained. Of course, for an expensive material such as the platinum group metals, the use of a support material is the only viable option. The properties of the supported catalyst will be influenced by several factors [172]... 

Tab. 20.1 Chemical and physical properties of the platinum-group metals (PGM)... 

The platinum group metals (Ru, Rh, Pd, Os, Ir, and Pt), Ag, and Au are called precious or noble metals. Nobility and catalytic activity are unique properties of precious metals, that result in a wide range of applications, such as catalysts in various industrial fields, in electronic industries, and in jewelry. The chemical and physical properties of each precious metal are shown in Table 1. The determination of precious metals attracted the interest of analysts and developed rapidly because these metals are valuable and rare, and also very important for many products. Their concentration levels are very low in many natural sources, metallurgical intermediates, and environmental samples. Furthermore, precious metals are collectively handled in the analytical chemistry field, because of the close resemblance of their chemical properties and behavior. Precious metals are the subproducts in copper, zinc, or lead smelting and refining, which is the most important source of precious metals. Whereas many analytical methods for the ultratrace determination of precious metals in environmental or biological samples were recently published with the development of high-sensitivity analytical instruments, the classical fire-assay has been widely applied for the accurate determination of expensive precious metals. 

TABLE 1. Physical Properties of the Platinum Group Metals... 

Table 4.102. Selected physical and chemical properties of the six platinum-group metals (PGMs)... 

THE NOBLE METALS, or precious metals, consist of gold, silver, and the platinum group metals (PGM)— platinum, palladium, iridium, rhodium, osmium, and ruthenium. These metals are known for their stability in corrosive environments, physical beauty, and unique physical and chemical properties. They command a premium price because of their low abundance in nature. The noble metals are used in many applications with great success and often with few, if any, substitutable materials. 

Iron (Fe), cobalt (Co) and nickel (Ni) are sometimes called iron group metals while ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt) are known as platinum group metals. Metals of each group have similar physical and chemical properties. Table 2.73 sununarizes some physical properties of group-VIII metals. 

Rhodium is a hard shiny-white metal that resists corrosion from oxygen, moisture, and acids at room temperatures. As a member of group 8 (VIII), Rh shares many chemical and physical properties with cobalt (j Co) just above it and iridium ( ylr) below it in the vertical group. Therefore, it is considered one of the elements that are transitory between metals and nonmetals. It is rare and only found in combination with platinum ores. 

Electronic configuration 1. v22522/763 23/7 3 l04 24/764 /5.s 1. Ionic rad ius Ru4+ 0,60 A. Metallic radius 1,3251 A. First ionization potential 7.5 eV. Other physical properties of ruthenium will be found under Platinum and Platinum Group. See also Chemical Elements,... 

Synthesis, reactions, and physical properties of stable mononuclear platinum and zirconium complexes of cyclohexyne reported prior to the late 1980s have been comprehensively covered in earlier reviews.2-8 More recently, reaction of the zirconocene complex of cyclohexyne with trimethyla-luminum and trimethylgallium has been reported to give 247 and 248, respectively [Eq. (36)].57-58 These products are novel because four atoms (carbons Cl and C3, the transition metal, and the main group metal) are covalently bonded to an sp2 hybridized carbon (C2) in a planar tetracoordi-nate fashion. Synthesis of this type of complex, which Erker describes as anti-van t Hoff/LeBel, does not require the strained cycloalkyne ring zirconocene complexes of acyclic alkynes react similarly.57-58... 

Hardness of the aimealed metals covers a wide range. Rhodium (up to 40%), iridium (up to 30%), and mthenium (up to 10%) are often used to harden platinum and palladium whose intrinsic hardness and tensile strength are too low for many intended appHcations. Many of the properties of rhodium and indium. Group 9 metals, are intermediate between those of Group 8 and Group 10. The mechanical and many other properties of the PGMs depend on the physical form, history, and purity of a particular metal sample. For example, electrodeposited platinum is much harder than wrought metal. 

Iridium is a third-row d-block metal and is the heaviest element in group 9. It is a hard, lustrous, silvery metal, discovered by Tennant in 1803 the name iridium derives from the Latin iris (rainbow). The element occurs as a native platinum alloy and in osmiridium (a native alloy of osmium, 15-40%, and iridium, 50-80%). Selected physical and chemical properties of Ir are given in Table 1. It is considered both as a platinum metal and as a precious metal. At room temperature, Ir is particularly resistant to corrosion. 

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