Amorphous selenium is found in three forms: black, glassy, obtained when liquid selenium is rapidly cooled, melted at 180 degrees centigrade with a density of 4.28 g/cm3; colloidal red, is obtained by carrying out reduction reactions and crystalline and gray selenium whose structure is hexagonal, this form is the most common, it melts at 220.5 degrees Celsius, its density is equal to 4.81 g/ cm3, This red form has a monoclinic structure, its density is 4.39 g/cm3 and it melts at 221 degrees Celsius.
Selenium is insoluble in alcohol and water but has slight solubility in carbon disulfide and is completely soluble in ether. This is the photoelectric effect in which light is converted into electricity. Its electrical conductivity increases when exposed to light. It is a p-type semiconductor material when below its melting point and in its natural form.
Electron configuration of selenium
Characteristics of Selenium
Selenium is used for different purposes, for example, ammonium selenium is responsible for making glass. Selenium sulfide is used in shampoos and lotions to treat seborrheic dermatitis. Selenium is defined as a micronutrient for all known life forms. It is found in cereals, bread, meat, fish, egg and potato shells, as well as lentils.
This element is present in the amino acid selenocysteine, it is also found in selenomethionine by replacing the sulfur that methionine and cysteine possess. It composes the enzymes peroxidase, glutathione, thioredoxin reductase and iodothyronine deiodinase.
It is also characterized by being an antioxidant, helps neutralize free radicals, stimulates the immune system, induces apoptosis and is part of the functioning of the thyroid gland. Research done suggests that there is a correlation between cancer prevention and selenium supplementation in humans.
Selenium deficiency is rare but can occur in patients with severe intestinal dysfunction or primarily on parenteral nutrition. Also in populations that feed on products grown in soils where there is not much selenium. The recommended daily intake for adults is 55-70 μg, consuming more than 55-70 μg may cause toxic effects.
Selenium is widely dispersed in the earth’s crust, mainly in soils and rocks. It is rarely found in its native state, being essentially obtained as a by-product of refined copper since it is found in electrolysis sludges, close to tellurium. The commercial production of this element is done by roasting with sulfuric acid or soda from the sludge.
Selenium is considered a dangerous element for nature because its compounds must be stored in dry areas, thus avoiding leaks that damage water. Selenium residues are treated with sodium sulphate in acidic solutions, heating them to subsequently obtain elemental selenium which has a lower bioavailability.
selenosis
This is caused by excessive consumption of selenium, this can be generated by ingesting more than 200 ug of this ion per day. Symptoms of selenosis are loss of nails and hair, loss of teeth, skin lesions and central nervous system abnormalities. In most cases, selenosis is concomitant with fluorosis.
