Tellurium oxide TeO

Analogous oxides are known containing one atom of sulphur replaced by selenium or tellurium. The tellurium compound, tellurium sulphoxide, STeOa, decomposes with production of tellurium monoxide, TeO, when gradually heated in a vacuum to 225° C.8 Attempts to produce sulphur monoxide similarly from sulphur sesquioxide have not been successful. 

Oxygen forms three oxides, TeO, Te02, and TeOj. The first two are somewhat basic in nature and are represented by numerous salts in which tellurium is bivalent or quadrivalent, respectively. The dioxide and the trioxide are both mainly acidic in character, although a few hexavalent salts of tellurium are known. 

Tellurium monoxide, TeO, is obtained by heating TeSOj in a vacuum to 230°, sulfur dioxide being evolved. It is amorphous, brown to black in color, and is easily oxidized. 

II. Calaverite—461 °C endotherm, calaverite decomposes and is transformed to Au and Te 671 °C exotherm, tellurium oxidizes and is transformed to TeO, at a temperature higher than 800 °C, TeOj sublimes 1071 "C endotherm, gold melts. 

Tellurium burns in air with a greenish-blue flame. The combustion product is dioxide, Te02, the most stable oxide of the metal. Tellurium also forms other oxides the monoxide, TeO, the trioxide, TeOs, and the pentoxide, Te205. Monoxide has not yet been obtained in solid form. Like sulfur and selenium, tellurium forms oxyacids. Such oxyacids include orthotelluric acid, HeTeOe and tellurous acid, H2Te03, in which the metal is in +6 and +4 valence states respectively. 

Oxides of composition TeO, TeOa and Te03 are known, as well as a fourth compound, Tea07, which appears to be a basic tellurium tellurate,... 

While total inorganic selenium in seawater increases with depth, total inorganic tellurium (Te) is highest at the surface and decreases with depth. Although the +VI oxidation state is more abundant than the +IV state for both Te and Se, in contrast to Se and SeIV, Te is thermodynamically less stable than Te (Lee and Edmond, 1985). The two coexisting oxidation states of Se occur as tetrahe-drally (Se ) and pyramidally (Se ) coordinated forms whereas Te and Te are found in octahedral and tetrahedral coordination, respectively. Te, principally in the form of Te(OH)g and TeO(OH)5, decreases to values at depth that are approximately 50% of surface concentrations, while Te as TeO(OH)3 and Te02(0H)2- is approximately constant with depth. 

Without either spray droplets or flooded pathways, substantial fractions of radionuclides released from the degrading reactor fuel can be retained within the reactor coolant system. Results of some example calculation for radionuclide retention in the reactor coolant systems for various types of accidents are shown in Table III-l. The natural retention of radionuclide vapors oeeurs because the vapors either condense on surfaces or react with these surfaces. Depending on the surface temperature and the duration of its exposure to high temperature steam, the surface material is either ehromium oxide (Cr203) or iron oxide (Fe304 y). Both of these materials are expected to be reactive toward cesium-bearing vapours and strontium or barium vapors. Stainless steel lead screws above the core at Three Mile Island were found to have captured cesium by reaction with silica impurities in the steel. Metallic nickel inclusions in the oxide films on surfaces within the reactor coolant system are reactive toward tellurium whether it is in the metallic state or present as TeO or SnTe. 

The controlled-potential oxidation of selenium and tellurium has been studied extensively by Lingane and Niedrach (222). Both selenium and tellurium (—II) undergo well defined two-electron oxidation processes at all pH values. For selenium (—II) the primary anodic reaction seems to involve oxidation of the mercury electrode followed by formation of HgSe while tellurium (—II) seems to be directly oxidized to tellurium metal. In strongly alkaline solution tellurium (—II) appears to undergo an additional incomplete oxidation to TeOs-... 

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