Amalgam forming metals

About 20 amalgam-forming metals, including Pb, Sn, Cu, Zn, Cd, Bi, Sb, Tl, Ga, In and Mn, are easily measurable by stripping strategies (ASV and PSA) based on cathodic deposition onto mercury electrodes. Additional metals, such as Se, Hg, Ag, Te and As are measurable at bare solid electrodes such as carbon or gold. 

Reactions of Amalgam-Forming Metals on Thin Mercury Film Electrodes... 

While early ASV schemes were limited to about a dozen amalgam-forming metals, the recent development of adsorptive stripping procedures has greatly expanded the scope of stripping analysis to more than 40 trace metals. 

Finally, since polarography involves mercury, which often solvates metals as amalgams, there can be a significant difference between the potential E° of standard tables and the appropriate value of E° for an amalgam-forming metal. Polarography therefore uses so-called half-wave potentials EU2 instead of standard potentials E°. All the above effects are incorporated in spreadsheet exercise 6.10. 

The reduction of lactones of polyhydroxy carboxylic acids to the corresponding aldoses with sodium amalgam can be successfully achieved by electroreduction at a mercury cathode, provided that the catholyte contains salts of amalgam-forming metals. The electroreduction of the lactones of n-ribonic and n-arabinonic acids to n-ribose and n-arabinose, respectively, is performed at a mercury cathode, with sodium, potassium, or zinc sulfate (or their mixtures) as the catholyte, and platinum gauze as the anode, immersed in aqueous, 15% sulfuric acid. The electrolyzer compartments are separated by a diaphragm, and the electrolysis is performed with intensive stirring of the catholyte, which is maintained at a temperature of +5 to +12° and at a constant pH (adjusted by additions of dilute sulfuric acid). Yields of monosaccharide are increased by addition of boric acid to the reaction mixture. 

For cations of amalgam-forming metals and for anions forming slightly soluble compounds with mercury, the sensitivity of polarographic techniques can be increased by accumulating the material within the electrode (as an amalgam) or at the surface... 

Amalgams are metallic systems in which mercury is one of the components. The solubility of the alkali metals, the alkaline earths, the rare earths and Au, Zn, Cd, Ga, In, n, Sn, Pb, Bi, Ru, Rh, and Pt in mercury is higher than 0.1 atom % [1]. A reversible redox reaction of an amalgam-forming metal ion on a mercury electtode... 

Applications of anodic stripping voltammetry, are chiefly for the determination of trace amounts of amalgam-forming metals (Fig. 5), while cathodic stripping voltammetry is used for determining species that form insoluble salts with mercury. The preconcentration stage allows determination in the concentration range 10 tolO M. 

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