Tellurium vapor

Metal tellurides for semiconductors are made by direct melting, melting with excess tellurium and volatilizing the excess under reduced pressure, passing tellurium vapor in an inert gas carrier over a heated metal, and high temperature reduction of oxy compounds with hydrogen or ammonia. 

Te2 (g). At temperatures above the boiling point, tellurium vapor is diatomic. The vapor pressure data of Doolan and Partington,1 which were obtained at lower temperatures, do not extrapolate to the known boiling point, and indicate higher association of the vapor. See also Deville and Troost.4 These data lead to the values V = —28.0600 and — 20.01500, whence, for Te2 (g), Qf= —24. This value is not very certain. 

Tellurium vapor d or tellurium tetrabromide combined with trifluoromethyl radicals, generated from hexafluoroethane in an electrical discharge, to form bis[trifluoromethyl] tellurium. 

Inhalation of tellurium vapor and tellurium hydride causes irritation of the respiratory tract. Exposure of rats, rabbits, and mice to tellurium hexafluoride caused pulmonary edema [20]. In addition to this, elemental tellurium can cross the blood-brain and placental barriers in rats [21]. 

In principle, tellurium deposition on stainless steel in the primary system would largely prevent this element from being released to the containment. However, tellurium vapor could react chemically with a variety of metallic aerosols to form tellurides in particular it has a high affinity for silver and cadmium, as well as for tin volatilized from the Zircaloy claddings. Thus, tellurium transport through the primary system would be primarily controlled by aerosol transport characteristics. Spence and Wright (1987) have calculated that inclusion of these processes of depo-... 

Tellurium breath (safety) A bad case of halitosis resulting from breathing tellurium vapor. 

Gases and vapors of volatile liquids can be introduced directly into a plasma flame for elemental analysis or for isotope ratio measurements. Some elements can be examined by first converting them chemically into volatile forms, as with the formation of hydrides of arsenic and tellurium. It is important that not too much analyte pass into the flame, as the extra material introduced into the plasma can cause it to become unstable or even to go out altogether, thereby compromising accuracy or continuity of measurement. 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

Tellurium Tetrabromide. Tellurium tetrabromide [10031-27-3] TeBr, forms yellow hygroscopic crystals which decompose above 280°C and melt at 363°C under bromine vapor. It boils at 414—427°C, dissociating into TeBr2 and bromine. It is soluble in ether and chloroform but not in CCl, and is readily hydroly2ed in water. 

With the exception of the reactions of trifluoromethyl radicals with sulfur vapor, which is really a separate class of reactions, if the power supplied to the load coil surrounding the reactor (see Fig. 2) was maintained at, or near, the minimum amount needed to support the discharge, in only two cases were compounds found that clearly resulted from reactions other than replacement of halogen by trifluoromethyl. The reaction of tellurium tetrabromide (or the chloride) gave, in addition to the products just reported, very small proportions of such species as BrCF2TeCF2Br and (C2F5)2Te, which were isolated in yields of... 

Liquid tellurium boils at 990 °C to a golden yellow vapor, with density that corresponds to the molecular formula T 2- Likewise, in polonium vapor only P02 species are present. Clearly, the decreasing complexity of the solid state of the three elements Se, Te, and Po, as compared to sulfur, is reflected in the vapor state. 

Sulfur vapor consists of a mixture of species that includes S8, S6, S4, and S2 (which like 02 is paramagnetic). Because the S8 molecule is nonpolar, it is soluble in liquids such as CS2 and C6H6. Selenium also consists of cyclic molecules that contain eight atoms, and tellurium is essentially metallic in character. In their vapors, several species are found that contain 2, 6, or 8 atoms. Both are useful as semiconductors, and selenium has been used in rectifiers. Because the electrical conductivity of selenium increases as the intensity of illumination increases, it has been used to operate electrical switches that open or close as a light beam is broken. Selenium was also used in light meters, but other types of meters are now available that are more sensitive. Table 15.1 gives a summary of the properties of the group VIA elements. 

Certain volatile elements must be analyzed by special analytical procedures as irreproducible losses may occur during sample preparation and atomization. Arsenic, antimony, selenium, and tellurium are determined via the generation of their covalent hydrides by reaction with sodium borohydride. The resulting volatile hydrides are trapped in a liquid nitrogen trap and then passed into an electrically heated silica tube. This tube thermally decomposes these compounds into atoms that can be quantified by AAS. Mercury is determined via the cold-vapor... 

All forms of tellurium are toxic in gas form. The vapors of all the compounds of the dust and powder forms of the element should not be inhaled or ingested. When a person is poisoned with tellurium, even in small amounts, the breath will smell like garlic. 

C to a bright red vapor. The solid is stable when pure. It disproportionates in oiganic solvents and is decomposed by acids and alkalies. It is hydrolyzed to H2Te03, Te, and HC1, and decomposed by HC1 to Te and H2TeCl6 [17112-43-5]. Air oxidizes tellurium dichloride to Te02 and HCL... 

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. 

The similar behavior of CO and CHO in reactions 0 + C2H and O + C2H provided confirmation to the conclusion that the same CH2 radical is formed by the primary steps of these reactions. In an earlier work4 (using discharge in H20 vapor involving less 02 molecules in the reaction vessel), the formation of CH2 in a reaction of O atoms with C2H4 was evident from its effect on a tellurium mirror. The reaction yielding... 

The atoms of all three elements show considerable tendency to polymerisation, both in the vaporous state and in solution in various solvents. In the vaporous state, sulphur appears to exist as Ss, S, , S2 and S molecules in varying proportions depending upon the conditions selenium behaves similarly, but tellurium vapour appears to consist mainly of Te2 and Te molecules. 

High Temperature Measurements of the Rates of Uptake of Molybdenum Oxide, Tellurium Oxide, and Rubidium Oxide Vapors by Selected Oxide Substrates... 

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