Silver compounds base metals

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

The most successful class of active ingredient for both oxidation and reduction is that of the noble metals silver, gold, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum and palladium readily oxidize carbon monoxide, all the hydrocarbons except methane, and the partially oxygenated organic compounds such as aldehydes and alcohols. Under reducing conditions, platinum can convert NO to N2 and to NH3. Platinum and palladium are used in small quantities as promoters for less active base metal oxide catalysts. Platinum is also a candidate for simultaneous oxidation and reduction when the oxidant/re-ductant ratio is within 1% of stoichiometry. The other four elements of the platinum family are in short supply. Ruthenium produces the least NH3 concentration in NO reduction in comparison with other catalysts, but it forms volatile toxic oxides. 

As regards other coordination compounds of silver, electrochemical synthesis of metallic (e.g. Ag and Cu) complexes of bidentate thiolates containing nitrogen as an additional donor atom has been described by Garcia-Vasquez etal. [390]. Also Marquez and Anacona [391] have prepared and electrochemically studied sil-ver(I) complex of heptaaza quinquedentate macrocyclic ligand. It has been shown that the reversible one-electron oxidation wave at -1-0.75 V (versus Ag AgBF4) corresponds to the formation of a ligand-radical cation. Other applications of coordination silver compounds in electrochemistry include, for example, a reference electrode for aprotic media based on Ag(I) complex with cryptand 222, proposed by Lewandowski etal. [392]. Potential of this electrode was less sensitive to the impurities and the solvent than the conventional Ag/Ag+ electrode. 

Alkynylsilver compounds are readily accessible from AgN03 and HC=CR in methanol or water in the presence of base. They are thermally stable. Like many heavy metal acetylides, silver compounds of unsubstituted acetylene are shock sensitive and explosive. 

Trithiane, S3(CH2)3 a chair-shaped molecule like cyclohexane, forms many metal complexes. Two silver compounds have layer structures based on the 6-gon net. In both structures Ag is tetrahedrally coordinated, the fourth ligand (X in Fig. 3.23(a)) being H2O in Ag(trithiane)C104. H2O and 0 of NOJ in Ag(tri-thiane)N03. H2O (JCS A 1968 93). Silver tricyanmethanide, Ag[C(CN)3], has a... 

DIHYDROXYBUTANEDIOIC ACID (87-69-4) C4H6O6 Combustible solid (flash point 410°F/210°C Fire Rating 1). Reacts violently with strong oxidizers, bromine, 90% hydrogen peroxide, phosphorus trichloride, silver powders or dust silver compounds. Mixture with some silver compounds forms explosive salts of silver oxalate. Aqueous solution reacts with bases, ammonia, amines, amides, inorganic hydroxides isocyanates, alkylene oxides, epichlorohydrin. Attacks some metals in the presence of moisture. 

---