Sodium selenates

The roasted pellets or extmdes are ground and leached in water. The hexavalent selenium dissolves as sodium selenate [13410-01 -0] Na2Se04. Sodium teUurate, being highly insoluble in the now very strongly alkaline solution, remains in the residue. The separation between selenium and tellurium is readily achieved, provided all tellurium is oxidized to the hexavalent state. 

Chromium Plating. Sodium selenate or selenic acid are added to chromium-plating baths to improve corrosion protection from pitting. 

Sodium selenate has been used on a small scale in commercial greenhouses, primarily for growing carnations and chrysanthemums. It is transformed by the plants into volatile selenides, which repel red spiders, mites, thrips, and aphids (see Insect control technology). Sodium selenite is not intended for crops which could ultimately be used as food for humans or domestic animals. 

Silver Selenate. Silver selenate, Ag2Se04, is prepared from silver carbonate and sodium selenate (see Seleniumand selenium compounds). 

A proprietary tetrachromate bath has been used in Germany under the name of the D process. By the use of additions of magnesium oxide and sodium tungstate it is claimed that the current efficiency of the bath can be raised to as high as 35-40%. Other additives such as indium sulphate, sodium selenate or sodium hexavanadate enable bright deposits to be obtained. 

Deficiencies were usually prevented or reversed by supplements with sodium selenate or selenite at 100 pg Se/kg ration, or 20 pg Se/kg body weight administered parenterally. 

Chickens, ducks 100 pg/kg DW ration as sodium selenate or selenite 37... 

Rees CB, Thode HG (1966) Selenium isotope effects in file reduction of sodium selenite and of sodium selenate. Can J Chem 44 419-427... 

Compounds Selenium dioxide selenium trioxide selenium oxychloride sodium selenite sodium selenate hydrogen selenide selenic acid selenium sulfide selenium disulfide... 

Reaction with sodium selenate yields lead selenate, PbSe04. Similarly, with sodium selenite or selenious acid, the product is lead selenite, PbSeOs. 

Alternatively, raw anode slimes are aerated with hot dilute sulfuric acid to remove copper. Slimes are then mixed thoroughly with sodium carbonate and roasted in the presence of sufficient air. Sodium selenate formed is leached with water. Hydrochloric acid is added to this selenate solution. Treatment with sulfur dioxide precipitates elemental selenium. Alternatively, the selenate solution is evaporated to dryness. Sodium selenate is reduced to sodium selenide by heating with carbon at high temperatures. Sodium selenide is leached with water. Air is blown over the solution. Selenide is oxidized to elemental selenium which precipitates. 

When fused with caustic soda or caustic potash, sodium selenate, or potassium selenate, Na2Se04, or K2Se04 is obtained. 

DeYoimg DJ, Bande JA, Eort DJ (1991) Assessment of the developmental toxicity of ascorbic acid, sodium selenate, comnarin, serotonin, and 13-cis retinoic acid using FETAX. Drug Chem Toxicol 14 127-141... 

Highly toxic groups will be found. They may be used to step up old nematocides or bring new ones to the fore. However, soil nematocides are contact killers and as such will be supplanted by chemotherapy. Plants will be fed materials toxic to the nematode. Such chemicals (stomach poisons) are already here, as indicated by sodium selenate. Plant parasitic nematodes can bathe in it, but unless it is absorbed by the plant and thus fed to the nematode, no injury is done. The mode of action of parathion is still uncertain. Plant parasitic nematodes placed in a saturated aqueous solution certainly survive for long periods, yet it has been found effective in the control of certain nematodes in living plants 16y 0), The next step is the introduction into the plant of nutriments to replace those taken from the plant by the nematode. The final step is the introduction into the plant of neutralizers of nemic enzymes. This may have already been done in the case of parathion, for it is said to inhibit cholinesterase formation in other animals. Chemotherapy will then have its day, but when that day is done physics may be expected to take over liie burdens of the control of plant diseases. We can expect the use of ultrasonics and radioactive fertilizers. 

Sodium selenate (see Selenium and selenium compounds) Sodium selenite (see Selenium and selenium compounds) Sodium silicofluoride (see Fluorides)... 

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