Cadmium oxide

A third group includes silver—nickel, silver—cadmium oxide, and silver—graphite combinations. These materials are characterized by low contact resistance, some resistance to arc erosion, and excellent non sticking characteristics. They can be considered intermediate in overall properties between silver alloys and silver or copper—refractory compositions. Silver—cadmium oxide compositions, the most popular of this class, have wide appHcation in aircraft relays, motor controllers, and line starters and controls. 

Eigure 11 illustrates the superior conductivity of P/M silver—nickel or silver—cadmium oxide contacts when compared with contacts made by standard melting techniques and formed from soHd-solution alloys. 

Almost all the methods described for the nickel electrode have been used to fabricate cadmium electrodes. However, because cadmium, cadmium oxide [1306-19-0], CdO, and cadmium hydroxide [21041-95-2], Cd(OH)2, are more electrically conductive than the nickel hydroxides, it is possible to make simple pressed cadmium electrodes using less substrate (see Cadmium and cadmium alloys Cadmium compounds). These are commonly used in button cells. 

The positive plates are siatered silver on a silver grid and the negative plates are fabricated from a mixture of cadmium oxide powder, silver powder, and a binder pressed onto a silver grid. The main separator is four or five layers of cellophane with one or two layers of woven nylon on the positive plate. The electrolyte is aqeous KOH, 50 wt %. In the aerospace appHcations, the plastic cases were encapsulated in epoxy resins. Most usehil cell sizes have ranged from 3 to 15 A-h, but small (0.1 A-h) and large (300 A-h) sizes have been evaluated. Energy densities of sealed batteries are 26-31 W-h/kg. 

Although it is only slowly oxidized in moist air at ambient temperature, cadmium forms a fume of brown-colored cadmium oxide [1306-19-0] CdO, when heated in air. Other elements which react readily with cadmium metal upon heating include the halogens, phosphoms, selenium, sulfur, and tellurium. The standard reduction potential for the reaction... 

Cadmium is usually plated from a cyanide bath that consists of an aqueous solution of cadmium oxide (35 g/L) and sodium cyanide (75 g/L). An additive and a brightener are used to produce smooth, fine-grain deposits. Current density ranges from 1.4 to 3.7 A/dm, depending on the concentration of cadmium cations in the electrolyte. 

Silver containing 2.5—15% cadmium oxide is used extensively for producing electrical contacts (see Electrical connectors). 

Naturally occurring cadmium compounds are limited to the rare minerals, greenockite [1317-58 ] CdS, and otavite (1), an oxycarbonate, but neither is an economically important source of cadmium metal or its compounds. Instead, cadmium compounds are more usually derived from metallic cadmium [7440-43-9] which is produced as a by-product of lead—2inc smelting or electrolysis (see Cadmiumand cadmium alloys). Typically, this cadmium metal is burnt as a vapor, to produce the brown-black cadmium oxide [1306-19-0], CdO, which then acts as a convenient starting material for most of the economically important compounds. 

The use of a catalyst such as cadmium oxide increases the yield of dibasic acids to about 51% of theoretical. The composition of the mixed acids is about 75% C-11 and 25% C-12 dibasic acids (73). Reaction of undecylenic acid with carbon monoxide using a triphenylphosphine—rhodium complex as catalyst gives 11-formylundecanoic acid, which, upon reaction with oxygen in the presence of Co(II) salts, gives 1,12-dodecanedioic acid in 70% yield (74). 

Labeling. The typical labeling classification for frit may be followed by precautionary labeling for formulations containing lead oxide, free siUca, or cadmium oxide. Special labeling for shipment to specific locaUties may also be necessary to meet local and state requirements. 

Cadmium By-product of zinc and lead smelters Cadmium, cadmium oxide Baghouses... 

Dimethylsilicone rubbers show a high compression set which can be reduced to some extent by additives such as mercurous oxide and cadmium oxide. These materials are undesirable, however, because of their toxicity. Substantially reduced compression set values may be obtained by using a polymer containing... 

Beryllium compounds with the exception of aluminium beryllium silicates Cadmium oxide Cadmium sulphate... 

Fire Hazards - Flash Point Not flammable Flammable Umits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agems Not To Be Used Not pertinent Special Hazards cf Combustion Products Toxic hydrogen fluoride and cadmium oxide fumes can form Behavior in Fire Not pertinent Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Insoluble fluorosilicates are brought into solution by fusion with four times the bulk of fusion mixture, and extracting the melt with water. In either case, the solution is treated with a considerable excess of ammonium carbonate, warmed to 40 °C, and, after standing for 12 hours, the precipitated silicic acid is filtered off, and washed with 2 per cent ammonium carbonate solution. The filtrate contains a little silicic acid, which may be removed by shaking with a little freshly precipitated cadmium oxide. The fluoride in the filtrate is determined as described in Section 11.59. 

If an acid solution of a fluorosilicate is rendered faintly alkaline with aqueous sodium hydroxide and then shaken with freshly precipitated cadmium oxide, all the silicic acid is adsorbed by the suspension. The alkali fluoride is then determined in the filtrate. 

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