Germanium sulphides

Figure 2.2. Proposed architecture for mesostructured metal germanium sulphides. Adamantanoid clusters [Ge4S10]4 link upon addition of a metal salt to form a supra-molecular mesostructured material where surfactant molecules charge balance the negative charge on the framework. Reproduced with permission from [38].

Germanium traces were separated by co-precipitation with Fe(OH)3 [5]. Germanium sulphide has also been precipitated from 6 M HCl with Hg(II) or As(III) as collectors. 

Diethylberyllium Pyrophoric metals Germanium (II) sulphide Dichlor(ethyl)silane... 

Arsenic(III) sulphide, As2S3 Discussion. The arsenic must be present as arsenic(III), In this condition [ensured by the addition of, for example, iron(II) sulphate, copper(I) chloride, pyrogallol, or phosphorous(III) acid] arsenic may be separated from other elements by distillation from a hydrochloric acid solution, the temperature of the vapour being held below 108 °C arsenic trichloride (also germanium chloride, if present) volatilises and is collected in water or in hydrochloric acid. 

Aluminium B a 5 o B B < I Antimony a < Barium B a 1 3 Bismuth I Boron Cadmium 1 Caesium Calcium 1 Cerium Chloride, Chlorine [ Chromium X) o o C o a Gallium I Germanium Gold 1 Hafnium Hydrogen sulphide B a 5 a B a 5 a o 1 Lanthanons Lead f Lithium 1 Magnesium f Manganese Mercury Molybdenum... 

Ammonium sulphide) Barium sulphide Calcium sulphide Chromium (II) sulphide Copper (II) sulphide Diantimony trisulphide Dibismuth trisulphide Dicaesium selenide Dicerium trisulphide Digold trisulphide Europium (II) sulphide Germanium (II) sulphide Iron disulphide Iron (II) sulphide Manganese (II) sulphide Mercury (II) sulphide Molybdenum (IV) sulphide... 

Properties dependent on adsorption are not confined to conductivity. Luminescence of materials may be affected, as Ewles and Heap (7) have shown for the case of silica, for which the luminescent peak at 4000 A. was shown to be associated with the adsorption of the OID radical. Many workers have demonstrated the dependence of the contact potential on the adsorption of gases. For example, Brattain and Bardeen (8) have shown that the contact potential of germanium varies with the adsorption of water vapor. Photoconductivity may be dependent on the adsorption. For example, Bube has shown (9) that the adsorption of water vapor has a marked effect on the photoconductivity of cadmium sulphide. He concluded (10) that the effect was indirect surface changes affect the lifetime of the excess carriers, thus affecting the photoconductivity. Melnick (11), however, working with zinc oxide, has produced evidence that part of the photoconductivity in this case is directly associated with excitation from adsorption levels. 

SCHEME 24. Proposed mechanism for the copolymerization of a propylene sulphide and bis[bis(tri-methylsilyl)amido]germanium... 

Ge 2 p.p.m. Carbon is important in the atmosphere and is the major element of life. Germanium is widely but thinly distributed in silicate and sulphide minerals. 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

Zinc (0.02% of the earth s crust) occurs almost entirely as ZnS this has two forms (Fig. 277), the much commoner cubic zinc blende or sphalerite, and the rarer, hexagonal wurtzite (p. 149). Iron and cadmium are nearly always present as substitutional impurities and the ore also serves to concentrate a number of much rarer elements such as indium, gallium and germanium. The sulphide is easily converted to oxide by roasting in air. 

The term semiconductor covers a wide range of materials, including the elements silicon and germanium, and compounds such as oxides, sulphides, selenides, etc. A survey of the physics and chemistry of semiconductors is given in the book edited by Hannay and particular reference to semiconductivity and adsorption on oxide surfaces is to be found in an article by Gray . 

Figure 13,01 A comparison of the transmission ranges of Germanium Arsenic Sulphide (a), Selcnide (b) and Telluride (c) (2 mm thick) glasses (After Savage, 1985).

Fig. 1.22. Chromatograms of the products of chlorination of germanium ore with carbon tetrachloride. 1= Chlorine 2 = carbon dioxide 3 = phosgene 4 = carbon sulphide 5 = germanium tetrachloride 6 = carbon tetrachloride. From ref. 113.

The data were generally in accordance with the lists of elements emitted in the course of technological processes applied by particular works. The main zinc ores used in Poland such as sphalerite, ZnS, and galman, ZnC03 + ZnSi04-H20 are almost always accompanied by lead and cadmium compounds, and very often by copper, arsenic and antimony (Jedrzejowski, 1987). Germanium and tin compounds occur as additional components of sulphidic zinc and lead ores. 

Solids have traditionally been divided into three classes when the electrical properties are described. Those that conduct electricity well are called conductors. This group is typified by metals. Those solids that conduct poorly are called semiconductors. This group contains elements such as silicon and germanium, and large numbers of minerals such as the iron sulphide fool s gold, FeS2- Solids that do not conduct electricity are called insulators or dielectrics. Many oxides, such as magnesium oxide, MgO, and most polymers, such as polyethylene, are insulators. 

Thus carbon has only the highly reactive car-benes. Silicon forms analogous silyienes. Germanium has an unstable hydroxide (Ge(OH)2), a sulphide (GeS), and halides. 

---