Selenization

Selenates(IV) contain the [Se03] " and related sp>ecies. They are hydrolysed in solution and give complexes. 

Selenates are poisonous, selenic acid, H2Se04. See selenium oxyacids. 

Selenic acid, H2Se04. Formed by oxidation of selenates(IV) (CI2, Mn04 ). A strong acid similar to H2SO4 but loses O2 on heating. 

Selenious acid, H2Se03. Formed water on Se02. More stable than H2SO3, oxidized to H2Se04, reduced to Se by SO2. Gives selen-ates(IV) with oxides, hydroxides or carbonates. 

Selenium and tellurium react similarly, forming selenides and selenates(IV), and tellurides and tellurates(IV) respectively. Like the sulphide ion, S , the ions Se and Te form polyanions but to a much lesser extent. 

Tellurium trioxide, TeOa, is an orange yellow powder made by thermal decomposition of telluric(VI) acid Te(OH)g. It is a strong oxidising agent which will, like H2Se04, oxidise hydrogen chloride to chlorine. It dissolves in hot water to give telluric(VI) acid. This is a weak acid and quite different from sulphuric and selenic acids. Two series of salts are known. 

Gr. Selene, moon) Discovered by Berzelius in 1817, who found it associated with tellurium, named for the earth. 

The two absorption bands, at 1050 and 1400 cm , which appear in the Raman spectra of solutions of nitric acid in concentrated sulphuric acid are not attributable to either of the acid molecules. In oleum the lower band appears at 1075-1095 cm. That these bands seemed to correspond to those in the spectra of anhydrous nitric acid and solid dinitrogen pentoxide caused some confusion in the assignment of the spectrum. The situation was resolved by examining the Raman spectra of solutions of nitric acid in perchloric or selenic acids , in which the strong absorption at 1400 cm is not accompanied by absorption at about 1050 cm . Thus, the band at 1400 cm arises from the nitronium ion, and the band at about 1050 cm can be attributed in the cases of nitric acid and solid dinitrogen pentoxide to the nitrate ion formed according to the following schemes ... 

Picoline 129 2-Methyl-thiazole 128 2-Methvl-selen azole 149... 

Condensation of Selenated Alkylidene or Benzylidene Hydrazones or Pyrazolones with p-nitroso Dialkyanilines... 

Noncondensed aromatic or satured selenated heterocycles are little mentioned in NMR or mass spectrometry literature. 

HOONO peroxonitrous acid H2Se04 selenic acid... 

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