Arsenic, antimony and germanium

The neutral solution is purified to remove impurities more noble than zinc, e g., cadmium, copper, cobalt, nickel, arsenic, antimony, and germanium. The purification is accomplished by cementation in two or more steps with the addition of zinc dust. Generally, at least one cementation step is conducted at high temperature with arsenic, antimony, or copper-arsenic added. Cadmium is usually recovered in the metallic state and copper, nickel, and cobalt are recovered as sludges if present in sufficient quantities. 

Purification actually starts with the precipitation of the hydrous oxides of iron, alumina, siUca, and tin which carry along arsenic, antimony, and, to some extent, germanium. Lead and silver sulfates coprecipitate but lead is reintroduced into the electrolyte by anode corrosion, as is aluminum from the cathodes and copper by bus-bar corrosion. 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

As was the case with the volume The chemistry of organic arsenic, antimony and bismuth compounds, published in 1994, it was clear that the set of five volumes describing organometallic compounds (edited by Professor Frank R. Hartley) did not deal in sufficient depth with organic compounds of germanium, tin and lead. Hence we decided to publish the present volume, which we hope will be a useful and worthwhile addition to the series The Chemistry of Functional Groups. In this volume the authors literature search extended in most cases up to the end of 1994. 

M. Grotti, C. Lagomarsino and R. Frache, Multivariate study in chemical vapor generation for simultaneous determination of arsenic, antimony, bismuth, germanium, tin, selenium, tellurium and mercury by inductively coupled plasma optical emission spectrometry, J. Anal. At. Spectrom., 20(12), 2005, 1365-1373. 

L. Pauling and P. Pauling, On the valence and atomic size of silicon, germanium, arsenic, antimony, and bismuth in alloys. Acta Cryst. 9, 127-130 (1956). 

Arsenic, Antimony and Bismuth (W. Levason, G. Reid) Germanium, Tin and Lead (J. Parr)... 

The elements have been classified empirically based on similarities in their physical or chemical properties. Metals and nonmetals are distinguished by the presence (or absence) of a characteristic metallic luster, good (or poor) ability to conduct electricity and heat, and malleability (or brittleness). Certain elements (boron, silicon, germanium, arsenic, antimony, and tellurium) resemble metals in some respects and nonmetals in others, and are therefore called semimetals or metalloids. Their ability to conduct electricity, for example, is much worse than metals, but is not essentially zero like the nonmetals. 

Separation. — From most of the metals, germanium may be separated by the formation of the sulfo-salts with ammonium sulfide. It may be separated from arsenic, antimony, and tin by exactly neutralizing the sulfo-salts with sulfuric acid and filtering after 12 hours. Evaporate to small bulk, add ammonia, ammonium sulfate, and sulfuric acid and saturate with H. GeS2 precipitates while the other metals remain in solution. 

The post-transition metals (in their zero formal oxidation states) have a total of 10 + G valence electrons where G is the highest possible oxidation state of the post-transition metal. Thus, germanium, tin, and lead have 10 + 4 = 14 valence electrons arsenic, antimony, and bismuth have 10 + 5 = 15 valence electrons and selenium and tellurium have 10 + 6 = 16 valence electrons. 

Application of this procedure to the post-transition metals forming clusters indicates that bare gallium, indium, and thallium vertices contribute one skeletal electron bare germanium, tin, and lead vertices contribute two skeletal electrons bare arsenic, antimony, and bismuth vertices contribute three skeletal electrons and bare selenium and tellurium vertices contribute four skeletal electrons in 2D and 3D aromatic clusters. Thus, Ge,Sn, and Pb vertices are isoelectronic withBH, Fe(CO)-, andC5H5Co vertices and As, Sb, and Bi vertices are isoelectronic with CH, Co(CO)v and C H Ni vertices in bare metal cluster compounds. 

The elements that lie close to the "stair-step" line in Figure 3.7 often show a mixture of metallic and nonmetallic properties. These elements, which are called metalloids or semimetals, include silicon, germanium, arsenic, antimony, and tellurium. 

Antimony has three valences, 3, 4, and 5 Its chemical properties are very similar to those of arsenic. In other ways it stands close to the zinc group, particularly to the elements germanium and zinc. The likeness between antimony and germanium is so close that the discoverer of the latter at first called it Eka-antiniony of Olendelejeff. Analytically, antimony presents some difficulty in its separation from zinc. 

Metalloid is a term for elements that are sort-of metals, and sort-of not metals. Sometimes this group of elements is referred to as semimetals. To be more precise, these elements exhibit some of the physical and chemical properties of metals. Generally metalloids have some electrical conductivity, but not nearly as much as true metals. Because of these ambiguous definitions, even which elements are called metalloids can vary. Usually boron, silicon, germanium, arsenic, antimony, and tellurium are included as metalloids sometimes polonium and astatine rarely selenium. 

Davis, D. D., Gray, C. E., Alkali Metal and Magnesium Derivatives of Organo-Silicon, -Germanium, -Tin, -Lead, -Phosphorus, -Arsenic, -Antimony and -Bismuth Compounds, Organometal. Chem. Rev. A 6 [1970] 283/318. 

The properties of elements of the p-block vary greatly. At its right-hand end, the p-block includes all of the nonmetals except hydrogen and helium. All six of the metalloids (boron, silicon, germanium, arsenic, antimony, and tellurium) are also in the p-block. At the left-hand side and bottom of the block, there are eight p-block metals. The locations of the nonmetals, metalloids, and metals in the p-block are shown with distinctive colors in Figure 2.3. 

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