Selenium - what is it? The chemical element selenium. The use of selenium

What do we know about selenium? School chemistry class, we were told that selenium-a chemical element, we can solve various chemical equations and observe the reactions with its participation. But elements in the periodic table so much that the amount of information it is impossible to cover. So everything is set out quite briefly.

In this article you can get acquainted with the item called "selenium". What is it, what are its properties, where in nature we find this element and how it is used in the industry. In addition, it is important to know the impact it has on our bodies.

What is selenium

Selenium (the element Selenium) – is a chemical element, analogous to sulphur, which belongs to the 16 group (according to the earlier classification-6 th) of the periodic table. The atomic number of the element – 34, and atomic mass is 78,96. The item shows mainly non-metallic properties. In nature, selenium – it is a complex consisting of six isotopes, usually accompanied by sulphur. That is found in the production of sulfur. So mysterious selenium - what is it and how is it so valuable? It has many useful properties.

The history of the discovery of selenium

This chemical element was discovered by Swedish chemist and mineralogist Jens Jakob Berzelius in 1817.

In the scientific literature is the history of the discovery of the mineral, narrated by a scientist.

He says that while he along with another scientist named Johan Gottlieb Gan (which became famous as the discoverer of manganese, and studied its properties) conducted research on the method of production of sulfuric acid in Gripsholm.

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In the course of laboratory experiments in sulfuric acid was found precipitation of the red mixed with light brown substance. When interacting with a wide tube from the sedimentary material came easy radecky smell and formed lead Wren. The Berlin scientist Martin klaproth asserted that the presence of a characteristic odor indicates the presence of tellurium. A colleague of Berzelius also noted that in the mines where the extracted sulphur for acid (Felyne) also felt the same smell.

Hoping to find a newly opened rare metal (tellurium) in solution, researchers began more detailed examination of the sediment, but all was in vain. After Berzelius collected all products that have accumulated over several months the production of sulfuric acid by burning sulfur, and also began to explore.

Studies have shown that a new, previously unknown element has the properties similar to tellurium, but it is not. So the periodic table has got a new element - selenium.

Origin of name

The history of the origin of the name of the new element is quite interesting. Periodic table of elements defines a new element like Selenium (Se). Called on the name of our natural satellite.

Originally in Russian publications element called ‘selenium" (in the second decade of the nineteenth century). Later, after 1835, has taken the name "selenium".

Properties of selenium

Formula selenium-Se. The melting point of the substance – 217 (α-Se) and 170–180 degrees Celsius (β-Se), and it boils at a temperature of 685⁰.

The degree of oxidation, it manifests in the reactions: (-2), (+2), (+4), (+6), it is resistant to air, oxygen, water, hydrochloric acid and dilute sulphuric acid.

Amenable to dissolution in nitric acid of high concentration, Aqua Regia, longer dissolves in the alkaline medium oxidation.

Forms of selenium

There are two versions of selenium:

1. Crystalline (monoclinic selenium a - and b-forms of hexagonal selenium g-form).
2. Amorphous (powder, colloid and vitreous forms of selenium).

Modification of amorphous red selenium. What is it? One of the unstable versions of an element. Powdered and colloidal forms of selenium are obtained by recovery of a substance from a solution of selenous acid H₂SeO₃.

Black vitreous selenium can be obtain by heating element of any modifications to a temperature of 220 degrees Celsius with rapid cooling.

Hexagonal selenium has a gray color. This modification, the most thermodynamically stable, can also be obtained by heating to the melting temperature with further cooling to a temperature of 180-210 degrees Celsius. You need some time to withstand such a temperature.

The Oxide of selenium

There are a number of oxides that are formed by the interaction of selenium and oxygen: SeO₂ SeO₃,SeO, Se₂O₅. While SeO₂ SeO₃ – selenous anhydride (H₂SeO₃) and selenium (H₂SeO₄) acids, which form salts Selenite and selenate. Oxide of selenium, SeO₂ (dissolves in water) and is the most sustainable.

Interesting experiments on selenium

Before you begin your experiments with this element, it is worth remembering that any compounds with selenium is toxic, therefore it is necessary to take all security measures, for example, wear protective equipment and to carry out the reaction in a fume hood.

The Color of selenium is manifested in the course of the eye response. If using a flask with selenous acidmiss sulphur dioxide, which is a good reducing agent, the resulting solution becomes yellow, then orange and finally blood red.

A Weak solution will give the possibility to obtain amorphous colloidal selenium. In the case that the concentration of selenous acid is high, the reaction will settle from red to dark Burgundy colour powder. It will be powdered amorphous selenium basic form.

In order to give substance to a glassy state, it is necessary to heat and abruptly cool. The color will change to black, but the shade of red you will notice only if you look at the lumen.

Crystalline monoclinic selenium to be a bit more difficult. To do this, take a small amount of red powder and mix it with carbon disulphide. To the vessel with the mixture, you need to connect the reverse fridge and boil for 2 hours. Will soon begin to form a light orange liquid with a slight green tint will slowly evaporate in the container under the filter paper.

Selenium

For the First time the selenium began to be used in ceramic and glass industry. This tells us ‘Handbook of rare metals” 1965 edition.

Selenium is added to the glass mass with the aim of discoloration of the glass, eliminate the greenish hue that gives the admixture of iron compounds. To obtain the ruby glass in the glass industry is used a compound of selenium and cadmium (CdSe gadmocera). In the manufacture of ceramics will cadmould gives it a red color and color enamel.

Some selenium is used as a filler in the rubber industry and in the steel – to ensure that the obtained alloy had fine-grained structure.

Most semiconductor equipment is manufactured using selenium. This was the main reason for the growth in the value of such substances as selenium. The price increased from 3.3 to 33 dollars for 1 kilogram in 1930 and 1956 respectively.

Cost of selenium in the global market in 2015 was 68 dollars for 1 kg. whereas in 2012 the kilograms of this metal was worth about $ 130 per kilogram. The demand for selenium (price confirmation) crashes due to high demand.

The Substance is also widely used in the manufacture of photographic equipment.

The Availability of selenium in the human body

Our bodies contain approximately 10-14 milligrams of this substance, which is concentrated to a greater extent in such organs as the liver, kidney, heart, spleen, testicles and the cords in men, and also in the nuclei of cells.

The Need of the human body in trace element such as selenium is low. Only 55-70 micrograms for adults. Limit the daily dose is 400 micrograms. However, there is a disease called Kesan disease that occurs when the deficit of this element. Until about 60 years selenium was considered a toxic substance, which has a negative impact on the human body. But after a detailed study was made opposite conclusions.

Often when identifying pathological levels of selenium doctors can prescribe special preparations containing a combination of zinc-selenium-magnesium, substance, which together make up the deficiency of his body. Of course, not excluding foods that contain selenium.

Effects on the body

Selena has a very important role in the process of vital activity of organism:

• It activates the immune system – “stimulate” white blood cells more active effects on harmful microorganisms (viruses);
• Slow the aging process in the body;
• Reduces the risk of arrhythmia, sudden coronary death or oxygen starvation due to the slowing of the cholesterol oxidation;
• Accelerates blood flow to the brain, activating the mental activity, reduces symptoms of melancholy and depression (fatigue, lethargy, depression, and restlessness);
• Inhibits the growth of cancer cells, with antioxidant properties;
• Actively selenium fights free radicals;
• In interaction with vitamin E acts as an anti-inflammatory agent.

Of Course, it is impossible to ignore such an important property of the trace, as an aid in the fight against dangerous viruses: HIV/AIDS, hepatitis, Ebola.

Due to the presence of selenium, the virus lingers within the cell; the substance prevents the spread of the virus throughout the body. But if selenium is not enough, then its function does not work properly.

The Intake of selenium in complex with the iodine will help to stop the progressive disease of the thyroid gland (lack of thyroxine), and in some cases stimulates the regression of the disease (usually in children).

Also in medicine, selenium is used in the prevention of diabetes because it accelerates the consumption of glucose by the body.

The Drug with vitamins can be administered to pregnant women. It helps to cope with the symptoms of morning sickness, relieve fatigue and lift your spirits.

Selenium Deficiency

Why in the body can be a lack of such substances as selenium? What it is – “selenium deficiency” and how to deal with it? It really is a nasty disease, despite the fact that it occurs rarely.

It is Important to know thatthe worst enemy of this substance is, of course, carbohydrates – flour, sweet. In combination with these selenium is very poorly absorbed by the body and from this it may be the lack of it.

What are the signs of deficiency? First of all, it should be noted that in the deficiency of selenium will decrease the performance and overall mood.

The Lack of selenium weakens the immune system, whereby the body becomes more susceptible to various diseases, both mental and physical.

Also at deficiency of this substance in the body breaks down the process of absorption of vitamin E.

The Main signs of a lack of selenium are: pain in muscles and joints, premature fatigue, anemia, acute illness of the kidneys and the pancreas.

But if you feel any of the symptoms in any case should not engage in medical self-treatment. It is necessary to visit the doctor and consult about the need of acceptance of those or other drugs. Otherwise you can cause an excess of selenium, which is worse in some cases. For example, if the person with cancer is uncontrolled take selenium, chemicals (chemotherapy) may have no effect.

Excess selenium

Oversaturation of selenium also produces a negative effect on the body. The main symptoms of surplus are: loss of hair and nails, tooth damage, fatigue and constant nervous disorders, loss of appetite, dermatitis, arthritis, and yellowness and skin peeling.

But if you are not working on the production capacity of selenium, or don't live near the places where to get this substance, you can not be afraid of excess selenium in the body.

Food rich selenium

Most of selenium found in meat and liver – pork, beef, chicken, duck or Turkey liver. For example, in 100 grams of Turkey liver contains 71 and pork – 53 micrograms of selenium.

Per 100 grams of octopus meat contains about 44.8 mcg selenium. Also the diet should include foods such as shrimp, salmon, eggs, corn, rice, beans, fine ground barley and lentils, wheat, peas, broccoli, inactive bread-yeast (treated pre-heated until 60 degrees water). Do not forget about nuts-pistachios, almonds, walnuts and peanuts also contain selenium, even in small amounts.

It Should also be remembered that in food processing the substance is lost, preserves and concentrates contain two times less selenium than fresh food. Therefore, it is possible to consume as many fresh foods with selenium.