Ammonium tellurate

An ammonium tellurate with the empirical composition (NH4)20,2Te03,3H20 has been prepared by precipitation from solution, and its thermal stability in the temperature range 25—740 C studied. The sequence observed for the decomposition of the compound is shown in Scheme 2. °... 

When a drop of a caustic alkali solution containing AsOa , SbOg- or SnOg- is brought together with a drop of a freshly prepared solution of ammonium tellurate (which contains ions), there is an immediate precipitation of black elemental tellurium. The underl5dng reactions may be ... 

An acidic solution of tellurium (IV) or tellurium (VI) is treated with sulfur dioxide and hydrazine hydrochloride. Tellurium precipitated from solution can be estimated by gravimetry. Selenium interferes with this test. A volumetric test involves converting tellurium to tellurous acid and oxidizing the acid with excess ceric sulfate in hot sulfuric acid in the presence of Cr3+ ion as catalyst. The excess ceric sulfate is measured by titration with a standard solution of ferrous ammonium sulfate. 

The use of sulphur dioxide as precipitant was first proposed by Berzelius, but accurate results by this method are only obtainable under special conditions. Complete precipitation does not take place from a strongly acid solution, and in the presence of other metals small amounts of these are liable to be carried down. In the presence of heavy metals such as copper, bismuth and antimony, the following procedure has been recommended 2 The tellurium is oxidised to telluric acid by the addition of ammonium perdisulphate in the presence of potassium hydroxide, excess of perdisulphate being subsequently removed by boiling. The heavy metals present are next removed by means of hydrogen sulphide. The tellurium may then readily be estimated by reduction with hydrogen chloride and precipitation with sulphurous acid. 

Aryl tellurium halides combine with phosphonium halides, arsonium halides, or ammonium pseudohalides to produce aryl(dihalo)tellurates(II) or aryl(dipseudohalo) tellurates(II). 

Diorgano tellurium dihalides and ammonium, phosphonium, arsonium, or stibonium halides react in refluxing chloroform or ethanol to form onium diorganotetrahalo-tellurates(I V)5,1. When an onium halide with a halogen different from that in the diorgano tellurium dihalide was used, tetrahalotellurates with two different halogens in the molecule were isolated. 

Tellurate(IV) Diphenyl-tetrachloro-(Bis-[tetramethyl-ammonium (arsonium stiboniutn)] E12b, 669 (R2TeY2 + Xs)... 

For the synthesis of Mo/V/Te/Nb/O catalysts, ammonium paramolybdate, vanadyl sulfate, ammonium niobium oxalate and tellurium oxide or telluric acid are mixed as aqueous solutions or slurries and dried at about 150°C. These mixed slurries are then calcined at 500-650°C in a N2 stream [39]. In addition to the dominant Ml and M2 phases, impurity phases, for example M0O3, Mo,5V9O40 and Mo3Nb20ii, are also observed [28c]. It should be noted that Mo-V-Te-O catalysts cannot be obtained by the dry-up method. 

Chromotellurates, 2R 20.4Cr03.Te03, of sodium, potassium, and ammonium, have been prepared by spontaneous evaporation of an aqueous solution containing the eorresiDonding dichromate (1 molecule), chromium trioxide (2 molecules), and telluric acid (1 molecule). 

BFaN, Borate(III), tetrafluoro-, tetrafluoro-ammonium (1 1), 24 42 BFi303Te3, Tellurate(VI), pentafluorooxo-, boron(3 + ) (3 1), 24 35 BKCsHie, Borate(l-), (cyclooctane-1,5-diyl)dihydio-, potassium, 22 BLiCaHu, Borate(l-), (cyclooctane-1,5-diyl)dihydro-, lithium, 22 199 BNCaHia, Borane, (dimethylamino)diethyl-, 22 209... 

TeCl5(NHi)2 Ammonium hexa-chlorotellurate(IV), 2 189 TeFe Tellurium(VI) fluoride, 1 121 TeOa Tellurium(IV) oxide, 3 143 TeOeHe Telluric acid, 3 145, 147 Te(S2CN(CH,)2)2 Tellurium (II) dimethyldithiocarbamate, 4 93 Te(S2CN(C2H5)2)2 Tellurium (II) diethyldithiocarbamate, 4 93 Te(S2COCH,)2 Tellurium(II) methylxanthate, 4 93 Te(S2COC2H6)2 Tellurium(II) eth-ylxanthate, 4 93... 

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