Selenite salts

The selenite salts were prepared by precipitation from aqueous solution and well washed. Whether the specimen so obtained was crystalline or amorphous is not mentioned. The selenite was mixed with water and agitated intermittently for 1 h and the conductivity measured. The sampling and measurement were repeated until a constant value of the conductivity was obtained. No pH measurements were apparently made. 

Acute overdose. The oral mean lethal dose (MLD) of selenite salts in the dog is about 4 mg/kg. Ingestion of 1-5 mg/kg sodium selenite in five adults caused moderate reversible toxicity. Ingestion of as little as 15 mL of gun bluing solution (2% selenious acid) has been fatal. 

Sodium selenite (selenium trioxide) CASRN 10102-18-8 White powder Mean lethal dose of selenite salts In dogs 4 mg/kg. Human ingestion of 1-5 mg/kg sodium selenite caused moderate toxicity. 

The calcium selenite thus formed (equation 10) is, however, soluble in water to about 500 mg/1. Oxidation of calcium selenite to calcium selenate does not proceed to any significant extent, and even if it did, calcium selenate is even more soluble in water. Selenite salts of most common metals are also relatively soluble. Therefore, the treatment of the weak acid bleed by lime precipitation cannot achieve high removal levels of selenium. 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

Other oxoacid salts of the alkali metals are discussed in later chapters, e.g. borates (p. 205), silicates (p. 347), phosphites and phosphates (p. 510), sulfites, hydrogensulfates, thiosulfates, etc. (p. 706) selenites, selenates, tellurites and tellurates (p. 781), hypohalites, halites, halates and perhalates (p. 853), etc. 

Selenosulfate is an analogue of thiosulfate wherein one of the S atoms is replaced by a Se atom. Thiosulfate and selenosulfate anions are known to have tetrahedral structure as constituting the S and Se analogues, respectively, of the sulfate anion. The isomeric thioselenate anion SSeO " is not produced by the reaction of sulfur with selenite nor is the selenoselenate ion 86203 formed from selenium and selenite. Actually, SSeOj may be produced as a metal salt by boiling an aqueous solution of selenite with sulfur, but in aqueous solution thioselenates are not stable and isomerize to selenosulfates. 

Selenium is stable in water and in aqueous solutions over the entire pH interval in the absence of any oxidizing or reducing agent. Selenium can be electrochemically reduced to hydrogen selenide or to selenides that are unstable in water and aqueous solutions. It can be oxidized to selenous acid or selenites and further (electrolyti-cally) to perselenic acid (H2Se20s). Selenic and selenous acids and their salts are stable in water. The selenides, selenites, and selenates of metals other than the alkali metals are generally insoluble. 

The methodology most practiced is referred to here as codeposition, where a single solution contains precursors for all the elements being deposited and is reduced at a fixed potential or current density. The earliest report appears to be that by Gobrecht et al., which was published in 1963 [45]. Two anodes were used in the study, one of Se and one of Cd (or Ag), to form selenite and cadmium ions, respectively. CdSe was then formed by co-reduction of both species at the cathode. Reports of the formation of GaP in 1968 [46] and ZnSe in 1975 [47] via codeposition were subsequently published, and both involved molten salt electrolysis. 

The following year Julius Meyer reverted to the analysis of silver selenite. The analysis, however, was made by electrolytic deposition of the silver from a solution of the salt in potassium cyanide 2... 

Mercuric selenite., IIgSe03, prepared by the action of sodium hydrogen selenite on mercuric oxide, forms double salts of the types Na2Hg(Se03)2 and HgCl. SeOgNa.2H20.12... 

With the exception of the calcium, strontium, barium and mercurous salts, the normal selenates are readily soluble in water. Barium chloride and mercurous nitrate are therefore convenient precipitation agents.6 Barium selenate is, however, more soluble than barium sulphate, and also differs from the latter salt in being slowly reduced to selenite by hydrochloric acid 7 for these reasons precipitation with barium chloride is not applicable to the quantitative determination of selenie acid. A concentrated solution of selenie acid which has been saturated with barium selenate deposits crystals of barium selenie acid, H2[Ba(Se04)2].8... 

Reaction of Na2S03 with [Au(OH)4] gives [Au(S03)4]5- and the salt Na5[Au(S03)4]-5H20 has been isolated.51 This contains S-bonded sulfite, and can be reduced by excess sulfite to [Au(S03)2]3-. Selenite complexes of gold(III) are O-bonded, however.525... 

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