Tellurium dioxides

Tellurium dioxide is prepared by oxidation of elemental tellurium with concentrated nitric 

Tellurium dioxide is a white solid existing in two crystalline forms. It is soluble in water and in both aqueous sodium hydroxide and hydrochloric acid. 

The preparative methods are outlined in sequence and representative experimental procedures are described in later chapters. 

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Tellurium dioxide, Te02- Obtained by burning Te in air or heating tellurales(IV). Has rutile or brookile structures. Almost insoluble in water but gives tellurates(IV) with bases and, e g., TeCl4 with acids. 

Tellurium dioxide, Te02, is a white non-volatile solid obtained when tellurium is burnt in air. It is only slightly soluble in water but dissolves in alkalis to form salts. 

Tellurite, see Tellurium dioxide Tenorite, see Copper(II) oxide Tephroite, see Manganese silicate(l—)... 

EPM/EPDMcompounding pLASTOTffiRS, SYNTTiETIC - ETTTYLENE-PROPYLENE-DIENE RUBBER] (Vol 8) Tellurium dioxide [7446-07-3]... 

It is apparent from these equations that significant quantities of sulfur dioxide are generated. For selenium, the reaction shown for oxidation of elemental selenium reverses itself at the lower temperatures employed for water scmbbing, thus regenerating sulfuric acid. The tellurium dioxide remains in the sulfated slimes. 

Although this procedure yields tellurium as the same compound found in the original feedstock, the copper teUuride is recovered in a comparatively pure state which is readily amenable to processing to commercial elemental tellurium or tellurium dioxide. The upgraded copper teUuride is leached with caustic soda and air to produce a sodium teUurite solution. The sodium teUurite solution can be used as the feed for the production of commercial grade teUurium metal or teUurium dioxide. 

Tellurium is stUl recovered in some copper refineries by the smelting of slimes and the subsequent leaching of soda slags which contain both selenium and tellurium. The caustic slags are leached in water and, using the controlled neutralization process, tellurium is recovered as tellurium dioxide. 

To produce commercial (99.5%) tellurium, tellurium dioxide is dissolved in hydrochloric acid. The tellurium solution is saturated with sulfur dioxide gas to yield commercial tellurium powder, which is washed, dried, and melted. 

Commercial Products. Tellurium dioxide [7446-07-3] Te02 (79.9% Te theoretically), is made by heating an aqueous suspension of teUurous acid. The acid is purified, if necessary, by redissolving in caustic soda solution and neutralizing with sulfuric acid. 

Tellurium diethyldithiocarbamate [20941 -65-5] [(C2H3)2NC(S)S]4Te, is made by the reaction of diethylarnine, carbon disulfide, and tellurium dioxide in an alcohoHc solution. 

Tellurium dioxide [7446-07-3] M 159.6, m 733 , d 6.04. Dissolved in 5M NaOH, filtered and ppted by adding lOM HNO3 to the filtrate until the soln was acid to phenolphthalein. After decanting the supernatant, the ppte was washed five times with distilled water, then dried for 24h at 110° [Horner and Leonhard J Am Chem Soc 74 3694 7952]. 

Diaza-l,6-dioxa-6fl-tellurapentalenes 97 were obtained in 4—60% yields by oxidation of 1,3-diketone dioximes with tellurium dioxide (79BSF199). 

Discussion. This gravimetric determination depends upon the separation and weighing as elementary selenium or tellurium (or as tellurium dioxide). Alkali selenites and selenious acid are reduced in hydrochloric acid solution with sulphur dioxide, hydroxylammonium chloride, hydrazinium sulphate or hydrazine hydrate. Alkali selenates and selenic acid are not reduced by sulphur dioxide alone, but are readily reduced by a saturated solution of sulphur dioxide in concentrated hydrochloric acid. In working with selenium it must be remembered that appreciable amounts of the element may be lost on warming strong hydrochloric acid solutions of its compounds if dilute acid solutions (concentration <6M) are heated at temperatures below 100 °C the loss is negligible. 

Telluro-cyanide (presumably TeCN ) has been explored as a source of tellurium for electrodeposition of CdTe [14], on account of the possible advantage that this species is less likely than tellurium dioxide to oxidize the cathodically produced telluride ion. Bath solutions were prepared by dissolving powdered Te in a concentrated aqueous solution of KCN and adding CdCb and EDTA. Stoichiometric CdTe deposits, free of excess Te, were reported. 

Tellurium-containing donors, synthesis and manufacture of, 22 212 Tellurium-copper alloys, 24 425-426 Tellurium crystals, 24 405-406 Tellurium decafluoride, 24 419 Tellurium dibromide, 24 420 Tellurium dichloride, 24 419-420 Tellurium diethyldithiocarbamate, 24 411 Tellurium dimethylthiocarbamate, 24 428 Tellurium dioxide, 24 407-408, 409, 411, 420, 428... 

The pure form of tellurium burns with a blue flame and forms tellurium dioxide (TeO ). It is brittle and is a poor conductor of electricity. It reacts with the halogens of group 17, but not with many metals. When it reacts with gold, it forms gold telluride. Tellurium is insoluble in water but readily reacts with nitric acid to produce tellurous acid. If inhaled, it produces a garlic-like odor on one s breath. 

Tellurium dioxide (TeO ) is a whitish crystalline powder that is slightly soluble in water. It is also toxic when inhaled. 

The alkoxytrihaloteUurination of alkenes or cycloalkenes is afforded by treatment with tellurium dioxide/hydrochloric acid/alcohoF or with tellurium tetrachloride (or tetrabro-mide)/alcohol in carbon tetrachloride. ... 

Tellurium dioxide in acetic acid/lithium chloride reacts with 2 equiv of / or 5-hydroxy-olefins, giving tetrahydrofuran or tetrahydropyran dichlorotelluro derivatives. ... 

The reaction can be performed in an equimolar ratio, employing tellurium dioxide in alcoholic aqueous hydrochloric acid. The formed trichlorotelluro derivative is reduced without isolation to the corresponding ditelluride (see Section 3.23.2)d ... 

Bromobenzotellurophene ° A mixture of 2.0 g (19.6 mmol) of phenylacetylene, 1.0 g (6.3 mmol) of tellurium dioxide, 2.0 g (23 mmol) of lithium bromide aud 50 uiL of acetic acid is heated uuder reflux for 20 h, cooled to 20°C, aud poured iuto 150 uiL of diethyl ether. Aqueous sodium hydrogeu carbouate solutiou (5%) is added uutil all the acid has beeu ueutralized. The orgauic phase is separated, dried with auhydrous calcium chloride, fdtered aud evaporated. The browu, oily residue is dissolved iu a mixture of 30 mL of carbou tetrachloride aud 10 mL of petroleum ether (b.p. 30 0°C). Chloriue is carefully bubbled through this solutiou uutil precipitatiou of the product ceases. The yellow precipitate is filtered and recrystallized from acetonitrile. Yield 2.2 g (92%) m.p. 263-265°C. 

Serious cases of tellurium intoxication have not been reported from industrial exposure. Iron foundry workers exposed to concentrations between 0.01 and O.lmg/m complained of garlic odor of the breath and sweat, dryness of the mouth and metallic taste, somnolence, anorexia, and occasional nausea urinary concentrations ranged from 0 to 0.06 mg/1. Somnolence and metallic taste in the mouth did not appear with regularity until the level of tellurium in the urine was at least 0.01 mg/l. Skin lesions in the form of scaly itching patches and loss of sweat function occurred in workers exposed to tellurium dioxide in an electrolytic lead refinery. ... 

Six derivatives of this system have been reported. Compound (113) was obtained by successive nitration of 3,4-dimethoxyphenyl tellurium trichloride (112) and partial reduction of the resulting 6-nitro derivative of (112) (Equation (10)). Compounds (47a)-(47c) were obtained by reaction of the oximes (114a)-(114c) with tellurium dioxide (Equation (11)) <86USP4607000,87USP4661438). 

Also, telluric acid can be prepared by oxidation of tellurium or tellurium dioxide with a strong oxidizing agent such as hydrogen peroxide, sodium peroxide, chromic acid, or potassium permanganate in nitric acid. Molecular equations for overall reactions are shown helow ... 

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