Thallium compound

Metals form an enormous number of compounds (inorganic and or-ganometallic) with a wide variety of hazards of which many retain the toxic nature of their parent metal  

Inorganic, see Terminology, Inorganic, p.241 Iron oxide, spent (obtained from coal gas purification), see Coal, p.44 Iron sponge, spent (obtained from coal gas purification), see Coal, p.44 Metal, see Terminology, Metals, p.242 

Metal sulphides, see also Solid Bulk Materials, p.221 

Soluble, see Terminology, Solutions, p.247 Water-reactive, see Dangerous When Wet Materials and Division 4.3, p.58 

A large number of dangerous goods do not fit neatly into hazard classes 1 through 8, they contain a variety of different dangerous materials, or, because of their size or use, are transported with minimal or no regulation. 

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Intermetallic compounds with gallium are used as semiconductors. Indium is used to coat other metals to protect against corrosion, especially in engine bearings it is also a constituent of low-metal alloys used in safety sprinklers. The toxicity of thallium compounds has limited the use of the metal, but it does find use as a constituent of high-endurance alloys for bearings. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Thallium (1) salts are oxidized only by very powerful oxidizing agents, eg, MnO or Cl, iu acid solutions. The properties of the more important thallium compounds are Hsted in Table 2. 

ThaUous sulfate, thaUous nitrate, and thaUous and thaUic oxide are the main compounds produced in bulk quantities by Noah Chemical. Approximately 20 other thallium compounds are also available commercially from Noah Chemical, Cooper Chemical, and Alfa Products, Ventron Division, Thiokol Corporation, in research and production quantities. However, demand for thallium compounds is small and limited to such appHcations as synthetic or analytical reagents. 

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