Sodium selenite and selanate are the most common inorganic salts of selenium used as mineral supplements.Selenium rarely occurs in nature in its elemental form and its inorganic sodium compounds occur in nature in soils.
It is an essential trace mineral and its inorganic salts like sodium selenite and selenate are used as dietary supplements in animal feeds as well as human nutrient supplement formulations.As an chemical it has many industrial uses and in glass industry it is used to manufacture colorless glass.
Properties of sodium selenateSodium selenite is a colorless solid and is a salt.
It is highly water-soluble and is found in its anhydrous compound (Na2SeO3) form and its pentahydrate form (Na2SeO3(H2O)5).Its selenate compound is also a white/grey powder, slowly soluble in water with the chemical formula Na2SeO4.
Production and synthesis of Na2SeO3Its sodium compounds are by products of copper refining and accumulate as slime on the bottom of electrorefining tank.
By sulfuric acid roasting or soda ash roasting of the copper slime the inorganic salts of selenium are produced.
Its other salt can also be prepared by the reaction of sodium hydroxide with selenium dioxide.SeO2 + 2 NaOH → Na2SeO3 + H2O
Uses of inorganic selenium salt: sodium selenite and selenateSodium selenite and selanate are being used in animal feed formulations, agricultural applications and human nutrition.
The superior forms of selenium like Selenomethionine and enriched yeast are slowly replacing these in human and animal nutrition supplements.
Na2SeO4 form of selenium is almost completely absorbed by the gastro-intestinal tract, but greater amount of it is excreted in urine without utilization.
As for its other form of salt only about 50% of it is absorbed; however it is better retained in the body for utilization.Organic forms of selenium are well absorbed and well utilized by the body.
Precautions while taking sodium selenite and selenate supplementsSelenium is required in very small doses. Uninformed persons can exceed the upper limits and suffer selenosis.
In a multivitamin preparation, this salt may get reduced to element form by the presence of vitamin C.
Hence it is advised not to consume this trace mineral along with vitamin C.
Selenium absorption is also found to be decreased when this supplement is taken along with supplemental iron, zinc, and copper.
However sodium selenate form does not combine with these metals or vitamin C.Very high does of both of these compounds have been found to be mutogenic and carcinogenic in animal experiments.
Ecological impact of indiscriminate use of these sodium compounds.Human activities like irrigation of normally dry lands, mining activity and using selenium in many industries have created many ecological problems.
These sodium compounds in the soil is getting get dissolved in the agricultural and rain run off and the wetlands are becoming loaded with inorganic selenium salts affecting the water birds and fish.
Inorganic selenium - Sodium selenite and selenate (current topic).