Nickel-copper-platinum minerals with

Rich accumulations of both rare and common metallic elements make Proterozoic rocks a significant source of mineral wealth for North America, as on other continents. Chromium, nickel, copper, tin, titanium, vanadium, and platinum ores are found together in the onionlike layers of crystallized igneous rocks called layered intrusions. Greenstone belts are mined for copper, lead, and zinc, each of which is mixed with sulfur to form a... 

The reaction can be carried out in either the liquid or vapor phase, but the vapor phase process is more common. Catalysts used in the liquid phase are palladium, palladium with platinum, or nickel, or cobalt suspended in a solvent such as methanol, ethanol, or mineral oil. In the vapor phase process, a nonnoble metal catalyst is used. Metals such as copper or chromium with copper are used in either a fixed or fluidized bed reactor. 

Rubeanic acid (I) reacts in ammoniacal solution in its aci-form (II) with copper, cobalt and nickel salts giving insoluble colored compounds (see page 329). In solutions containing strong mineral acid, rubeanic acid reacts only with certain elements of the platinum group. With palladium and platinum salts, red crystalline precipitates are obtained they are inner complex salts (III) of a semi-aci-form of rubeanic acid. Ruthenium salts give a soluble blue compound, whose structure is not known. 

Natural occurrence. Rhodium is one of the rarest element in the Earth s crust with an abundance of 1 pg/kg (i.e., ppb wt.). Rhodium occurs in nature as a native metal along with other platinum-group metals in the native mineral iridosmine or in sulfide ores such as rhodite, sperrylite, and some copper-nickel ores. 

Platinum has a certain tendency to form sulfides and arsenides, as for instance in the minerals cooperite PtS and sperrylite PtASj. The incHnation of platinum to form sulfides has the consequence that platinum often occurs with copper and nickel ores, especially pendandite. The metals are, however, mainly found as metallic phases, alloys with each other, with gold and with iron. The important alloy osmiridium with high contents of osmium and iridium also occurs in nature. 

The corrosion behavior of non-ferrous alloys such as those based on nickel, cobalt, copper, zirconium, and titanium has been reviewed in detail in this chapter. Besides exotic materials such as tantalum and platinum, nickel-based alloys are the most resistant to corrosion by mineral acids, and they are especially resistant to localized corrosion in chloride-containing environments, which troubles stainless steels. Nickel-based alloys can broadly be divided into alloys, e.g. Ni-Mo (B-2, B-3) and Ni-Cu (alloy 400), that do not contain chromium, and are not, therefore, passivated under oxidizing conditions, and alloys, e.g. Ni-Cr-Mo (C-22, C-2000,59,686, etc.) and Ni-Cr-Fe (G-30, 825, etc.), that form a chromium oxide passive film under oxidizing conditions. Ni-Mo alloys such as B-3 have excellent corrosion resistance in hot reducing acids such as hydrochloric and sulfuric. Ni-Mo alloys cannot withstand oxidizing conditions such as nitric acid and hydrochloric acid contaminated with ferric ions. Ni-Cr-Mo alloys such as C-2000 alloy are multipurpose alloys that can be used both in reducing and oxidizing conditions. 

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