Subject selenates

Selenium has a complex chemistry in the environment because of its multiple oxidation states and variable surface adsorption properties. Qualitatively it is analogous to sulfur occurring in the oxidation states +6 (selenate, Se04 ), +4 (selenite, SeOs "), 0 (elemental selenium) and —2 (Se, selenide) The Se anion closely resembles S (radii 0.20 and 0.185nm, respectively) and is often associated with sulfide minerals. Also, like S, Se is subject to volatilization through biological methylation. 

By the action of hydrazine hydrate on a dilute solution of selenic acid, hydrazine hydrogen selenate may be obtained as a colourless compound which is not decomposed by boiling water, but which, when dry, explodes with great readiness when subjected to heat, to shock, or to fumes of hydrogen chloride. For this reason, before hydrazine hydrate is used in the analysis of selenium compounds (see p. 307), it is essential that selenic acid and selenates should be reduced to selenites by means of hydrochloric acid.3... 

No other thermodynamic data have been identified for scandium selenates. The data for ScSeO and Sc SeO )2 in [82WAG/EVA] most likely derive from [67KOL/1VA] and are therefore subject to the same criticism as the original data. 

Compound 68 was subjected to another annelation with MVK to give the tricyclic s/nro-ketone 21. It was also transformed to. sp/ro-dienone 72 via a selenation-elimination process. 

Hawrylak-Nowak B (2009) Beneficial effects of exogenous selenium in cucumber seedlings subjected to salt stress. Biol Trace Elem Res 132 259-269 Hawrylak-Nowak B (2013) Comparative effects of selenite and selenate on growth and selenium accumulation in lettuce plants under hydroponic conditions. Plant Growth Regul 70(2) 149-157. doi 10.1007/s 10725-013-9788-5... 

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