Tellurites, TeO

Tellurium is converted into the dioxide, Te02, by nitric acid. Like sulphur and selenium, it forms two anions, the tellurite, TeOf, and the tellurate, TeO -. 

Reactions of tellurites To study these reactions use a 0-1 m solution of potassium tellurite, K2Te03, or sodium tellurite, Na2Te03. 

Hydrogen sulphide brown precipitate of the disulphide, TeS2, from acid solutions. The sulphide decomposes easily into tellurium and sulphur, and is readily soluble in ammonium sulphide solution but insoluble in concentrated hydrochloric acid. 

Sulphur dioxide complete precipitation of tellurium from dilute (1-5m) hydrochloric acid solutions as a black powder. In the presence of much concentrated hydrochloric acid, no precipitate is formed (difference and method of separation from selenium). 

Iron(II) sulphate solution no precipitation of tellurium (difference from selenium). A similar result is obtained with hydriodic acid (KI + HC1). 

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Many samples have redox potentials such fiiat fiiey can be oxidized by iodine. Therefore, file iodine in file titrant may be consumed by readily oxidizable samples fiiat will give a false high value for file water content. Some common substances fiiat can be oxidized by iodine are ascorbic acid, arsenite (As02 ), arsenate (As04 ), boric acid, tetraborate (3407 ), carbonate (COs ), disulfite (8205 ), iron(ll) salts, hydrazine derivatives, hydroxides (OH ), bicarbonates (HCOs"), copper(l) salts, mercaptans (RSH), nitrite (N02 ), some metal oxides, peroxides, selenite (SeOs "), silanols (RsSiOH), sulfite (SOs ), tellurite (TeOs ), fiiiosulfate (8203 ), and tin(ll) salts. For situations such as fiiese where file material under analysis reacts wifii iodine, an oven can be used to liberate fiie moisture from file sample, which is fiieii carried into file reaction vessel and titrated wifiiout interference. 

TEL, Et4pb. Lead tetraethyl, fellurates Formally salts containing oxy-anions of tellurium. Tellurales(VI) contain octahedral [TeO ] " species and derivatives of these. Tellurates(IV), tellurites, contain [TeOa] " species. 

Tellurous add, HzTeO, does not exist as TeOj is insoluble in water. Tellurates(/V), tellurites containing (TeO,) " species can be formed from TeO, and bases. 

H2Te (hydrogen telluride, colorless), HTe (hydrogen telluride ion, colorless), Te (telluride ion, colorless), Te (ditelluride ion, red), Te" + (tellurous ion), HTeOj (telluryl ion), HTeO (acid tellurite ion, colorless), TeO " (tellurite ion, colorless), H2Te04 (telluric acid, colorless), HTeOJ (acid tellurate ion, colorless), TeO (tellurate ion, colorless). 

Sodium tellurate [10101 -25-8], N TeO (53.7% Te theoretically), is made by oxidizing sodium tellurite solution with hydrogen peroxide. The reaction is exothermic. 

Tellurates. The water-soluble alkali metal and alkaline-earth tellurates are prepared by chlorinating alkaline solutions of the tellurites or by heating solid tellurites with KN03, KQ03, or Pb02 to form, for example, potassium tellurate [7790-58-1], Iv-TeO,. The insoluble tellurates are made by... 

In aqueous chemistry, tellurium is mainly found as telluride (Te- ), tellurite (Te03 ), and tellurate (Te04 ). Zolotov et al. [19] developed an IC procedure for the separation of TeOi, and Te04 by a suppressed ion-chromatographic system. In the method, F interfered with the determination of TeO., while S04 " interfered with the determination of Te04. In a report by Chen et al. [20], a similar method was used to speciate tellurium. The detection limits for Te04 were very poor in both methods. The studies were confined only to standard solutions. 

The reactions of sodium tellurite and potassium tellurite with monosulphide sulphur in alkaline solution have been investigated. Stepwise complex formation was observed in the TeO -S -OH and TeO -S -OH systems. Thio-salts of Te with less than 3 ligands were found to be unstable and to disproportionate into tellurite and trithiotellurite ions. The most... 

Several attempts have been made to construct phase diagrams of the Hg, Cd, Te, 0 system. The earliest diagram constructed, however, contained only Cd, Te and 0 and were constructed from an effort to grow and characterize bulk crystals from various mixtures of CdO and TeO (Figure 11) (43). Two compounds found were reported as cadmium ditellurite (CdTe Og) and cadmium mono-tellurite (CdTeOj). The later was reported to have two phases with a transition occurring at 700°C. 

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