Tellurium content

Most commercial tellurium is recovered from electrolytic copper refinery slimes (8—16). The tellurium content of slimes can range from a trace up to 10% (see Seleniumand selenium compounds). Most of the original processes developed for the recovery of metals of value from slimes resulted in tellurium being the last and least important metal produced. In recent years, many refineries have changed their slimes treatment processes for faster recovery of precious metals (17,18). The new processes have in common the need to remove the copper in slimes by autoclave leaching to low levels (<1%). In addition, this autoclave pretreatment dissolves a large amount of the tellurium, and the separation of the tellurium and copper from the solution which then follows places tellurium recovery at the beginning of the slimes treatment process. 

Selenium and tellurium contents of sulfides are useful indicators for estimating /oj (Shikazono, 1974a, 1978b). The selenium content of sulfide is governed by the reaction. 

Tellurium metal, its alloys, minerals or the teUurides may be dissolved in warm concentrated sulfuric acid or cold fuming sulfuric acid to form a red color, the intensity of which is proportional to the tellurium content in the substance. When this red solution is poured into water, black elemental tellurium metal precipitates out of solution. Oxidized tellurium does not respond to this test. 

Elemental composition Te 79.95%, O 20.05%. The compound can be identified by its physical and x-ray properties. Tellurium content may be measured by digesting the dioxide in HCl or aqua regia, diluting the solution, and analyzing by AA or ICP. 

The concentration of tellurous cation in solutions containing increasing amounts of hydrochloric acid has been determined by potential measurements, using a tellurium electrode, the total tellurium content of the solutions being determined chemically.3 The concentration of the tellurium ion was found to increase as the fourth power of the concentration of the hydrogen ions, the relation being in accordance with the expression... 

This is isolated in the usual manner from di-p-anisyl telluride. It sinters at 180° C. and melts at 183° to 184° C. The crystals consist of four-sided columns, easily soluble in warm benzene, toluene, xylene or chloroform, less soluble in alcohols, carbon disulphide or carbon tetrachloride, insoluble in petroleum ether. Boiling with water for a prolonged period yields a product of which the tellurium content lies between that of the dichloride and that of the oxide. 

The subhalides of tellurium are an especially important class of solid state compounds, and they have been the subject of intensive studies, so that a rather complete picture of their chemistry and their properties has been obtained in recent years. Because of their high tellurium content they contain fragments of the homonuclear tellurium chains their modified tellurium structures are of great current interest with respect to possibly significant physical properties. Consequently, the results of various investigations on the synthesis of the compounds, on phase analysis by thermal methods, on crystal growth, on the structures, on spectroscopic, thermodynamic, optical, photoelectric, electrochemical properties have been reported in the last two decades. In a comprehensive review (237) all significant results are reported and discussed in detail so that the present chapter will be restricted to some selected and chemically important features. 

At present, the geochemistry of tellurium is unclear. The average tellurium content of crustal rock is 2 x 10 %. Tellurium is a component of intrusive and extrusive magmas, volcanic gases, and volcanic sulfur deposits, and is usually associated with sulfur and... 

The tellurium subhalides represent a group of recently discovered compounds which have been investigated by the methods of solid-state and structural chemistry. Because of their high tellurium content and their crystal structures containing homonuclear tellurium connections they have attained significance as modified tellurium structures . As a consequence, tellurium subhalides have been the subject of various investigations in the fields of solid-state and chemical physics. 

The crystal structures of tellurium subhalides are built up of structmal units presented in Fig. 19, Because of the high tellurium content of these compounds, sinularities with the latter and the structural properties of elemental tellurium could be expected and, in fact, were confirmed 5.47)... 

The maximum electron density was obtained for the InSb-InTe section [(1.5 0.15) 10 cm (77 K)] for a tellurium content C(l) 0.1 at.% in the melt. This electron density was confirmed after repolishing the samples and making repeated measurements on them at room temperature and liquid-nitrogen temperature. For a tellurium content of Co(I) = 0.12 at.% and above in the melt, a reduction in the maximum density of free electrons to 1 10 cm was observed for all sections. 

The basis for this preliminary hypothesis is provided by the data from an approximate estimate of the vacancy concentrations [11] in undoped and doped single crystals of indium antimonide, which we obtained by comparing the x-ray (px) a.nd e erimental (pe) densities (Table 2). As may be seen from the table, the vacancy concentration in undoped indium antimonide is about 2 10 cm, and this value is maintained for doped indium antimonide up to a free-electron density of (1.2-1.5) 10 cm (i.e., a tellurium content of about 2 10 cm ). Only with a further increase in tellurium concentration in the crystal does the vacancy concentration iincrease. Therefore, with a further increase in tellurium content in the solid solution, the limitation in the free-carrier density may be due to both precipitation of tellurium from the solid solution and the formation of compensating acceptor vacancies by the mechanism given in [2]. 

Few data are available on levels of tellurium in normal subjects. Determination of the whole-body tellurium content in adult humans by neutron activation analysis gave values of approximately 500 mg [9]. The whole-blood concentrations of tellurium in normal subjects have been reported to range from 0.15 to 0.3 ng/mL [10]. The normal urine tellurium concentrations were measured by hydride generation inductively coupled plasma atomic spectrometry and hydride generation atomic... 

One hundred milliliters of a urine sample is digested with nitric and perchloric acids. After the sample solution has become colorless, it is evaporated to dryness. One milliliter of HCl is added to the residue and evaporated to dryness. The residue is dissolved with 6 M HCl. The sample solution is introduced into a hydride generator and then generated tellurium hydride is passed to a quartz cell heated by flame. The absorption signal is recorded at 214.3 nm. The tellurium content in the sample solution is determined by the method of standard addition. The lower detection limit is 0.04 p,g/liter [12]. 

A hair sample (1 g) is washed with water, acetone, ether, and detergents followed by a successive rinse with water, acetone, and ether. After washing and drying the hair sample, it is digested with nitric, perchloric, and sulfuric acids. After digestion, the hydrochloric acid concentration of the sample solution is adjusted to 4 M, and it is boiled for 5 min. The tellurium content in the sample solution is determined by the hydride generation atomic absorption spectrometry described above. The lower detection limit is 1 ng/g and the levels of unexposed subjects are below the detection limit [13]. 

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