SELENIUM

From Big Medical Encyclopedia

SELENIUM (Selenium, Se) — chemical element VI of group of a periodic system of D. I. Mendeleyev, belongs to biogenic microelements. Pages and its connections are industrial poisons and represent considerable professional harm; radioisotope 75 Se use in medicine for a stsintigrafiya of a pancreas; in microbiology nek-ry salts C. use for preparation of mediums (see. Selenitovy environments ). The page serves as the catalyst in hydrogenation processes — dehydrogenations, carried out in laboratory and working conditions. It finds broad application in production of semiconductors, rectifiers, photo cells, thermoelements. In the glass industry of S. use as dye, in rubber industry — for curing of rubber, in metallurgy — etc.

S. was open for receiving alloy steels in 1817 by I. Bertselius and is called in honor of the Moon since this element was always found together with the tellurium (see) discovered earlier and called in honor of Earth.

In crust S.'s maintenance makes 6*10 - 3 weight. %. S.'s traces are found in natural sulfides: iron and copper pyrite, blende, galenite. Pure selenic minerals meet seldom. The most important of them — selenides: naumannpt (Ag 2 Se), clausthalite (PbSe), tiemannite (HgSe), berzelianite (Cu 2 Se). Even less often the Page meets native. Minerals C. have no industrial value, and S. receive as a by-product on medeelektrolitny, sulphuric acid and cellulose productions.

Sequence number of selenium 34, atomic weight (weight) 78,96. Selenium has 6 stable isotopes (see) with mass numbers 74 (0,87%), 76 (9,0%), 77 (7,6%), 78 (23,5%), 80 (49,8%), 82 (9,2%) and 17 radioisotopes with mass numbers from 68 to 91; isotopes C. have also 11 isomers (see the Isomerism). Half-lives of 23 radioisotopes and isomers C. matter from fractions of a second till 1 o'clock, half-life 75 Se, primenyaekhmy in medicine, is equal 118,5 days. 75 Se receive in the nuclear reactor radiation of a selenic target neutrons on reaction 74Se (n, s) 75 Se or on the accelerator radiation of arsenic protons or deuterons on reactions 75 As (r, n) and 75 As (d, 2n). 75 Se breaks up with electron capture and emission of gamma radiation in a wide power interval. Main 6 gamma lines 75 Se have energy E scale , equal 96,7 kev (3,1%); 121,1 kev (15,9%); 136 kev (54%); 264,6 kev (58%); 279,5 kev (25,2%); 400,6 kev (11,6%). Besides, there are 18 gamma lines, total intensity to-rykh makes less than 5%.

75 Se for radio isotope researches release in the form of selenate and sodium selenite, and for a wedge, uses — in a look 75 Se-selenometionina (see. Metionin ), a form of release — solution for injections.

75 Se belongs to isotopes of average group of radio toxicity. Minimum significant activity in a workplace which is not demanding registration or obtaining permission of bodies of the State sanitary inspection is equal 10 mkkyur (370 kBq).

The page represents substance, dark gray with a brown shade. A number of polymorphic modifications of S. is known (see. Polymorphism in chemistry ). At a usual temperature so-called gray, hexagonal S. is stable, to-ry it is constructed of spiral chains of Se atoms. From water solution of selenium allocate amorphous S. of red color, during the heating passing into a hexagonal form; t°pl of hexagonal selenium 217 °, t°kip 685 ± 1 °. Selenium is the typical semiconductor, the purest hexagonal S. at temperatures close to temperature of melting, about 104 ohms-cm have resistance. S.'s conductivity sharply increases during the lighting.

In chemical connections C. usually shows valency +4, +6 and — 2. At the room temperature of S. on air, in water and in the atmosphere of O 2 it is steady, does not react with the salt and diluted chamois to-tami, we will well dissolve in concentrated nitric to - those and to aqua regia, in alkalis C. it is dissolved slowly, with oxidation. At S.'s heating is oxidized with formation of dioxide (SeO 2 ) — selenious-acid anhydride, often S.'s oxidation is followed by burning (a flame of blue color). The page reacts with fluorine (at the room temperature), with chlorine and bromine (at small heating), practically does not interact with iodine C. Dioxide and trioxide (SeO 3 ) selenium are strong oxidizers. With halogens C. forms connections, very various on properties; tetrachloride and tetrabromide C. with alkali metals, ammonium, organic amines give complex connections. Selenouglerod (CSe 2 ) it is similar to carbon sulfur (see). Hydrogen selenide (H 2 Se) — hydrogen selenide — colorless gas with extremely off-flavor, surpasses in toxicity hydrogen sulfide (see). Salts selenious to - you (H 2 SeO 3 ) — selenit; salts selenic to - you (H 2 SeO 4 ) — the selenates on many properties reminding the corresponding sulfates during the heating decay with formation of selenit.

Numerous organic compounds C. are similar to the corresponding connections are gray (see).

Methods of definition of S. include qualitative tests and quantitative methods of definition. The most widespread qualitative test on S. is reaction of recovery of its muriatic solution sulfur dioxide gas, a hydrazine or hydroxylamine. The allocated elementary S. forms a characteristic red deposit. Quantitative colorimetric methods of definition of S. are based on measurement of intensity of the coloring of solutions appearing at S.'s recovery to an elementary state.

Pages carry to so-called possibly necessary to microelements (see), however S.'s role in life activity of the person is not found out yet. There is an assumption that S. as antioxidant participates in regulation of free radical processes in an organism, in particular in regulation of peroxide oxidation of lipids.

Professional harm

in the course of receiving and S.'s use couples and S.'s aerosols, Se dioxide can come to air of production rooms, and at nek-ry operations — and hydrogen selenide. At manual operations, at contact with the equipment and the products containing S. and its connections pollution of skin and clothes by them is possible.

Under production conditions S. and its connections get to an organism of hl. obr. through respiratory tracts, is more rare — through went. - kish. a path wriggle skin. Connections C. are easily soaked up and is long circulate in blood. They are capable to be deposited in all bodies, but is preferential in a spleen, a liver, kidneys, and also in skin and in hair. Out of S.'s organism it is brought slowly, within several years, generally through kidneys and went. - kish. a path, in insignificant degree — with expired air.

The page and all its connections are toxic. From inorganic compounds C. hydrogen selenide and selenium dioxide are especially toxic; its connections with metals are less toxic. On the nature of toxic action of connection C. resemble connections arsenic (see) also have polytropic effect with preferential damage of a liver, kidneys and c. N

of the village of Hron. S.'s poisoning and its connections is shown in the form of Qatar of upper respiratory tracts, bronchitis (see) with the phenomena of a bronchospasm (see), toxic hepatitis (see), cholecystitis (see), gastritis (see), a spastic colitis (see), astheno - a vegetative syndrome (see. Asthenic syndrome). In more expressed cases hron. S.'s poisonings note neuroendocrinal disturbances, an enlargement of the thyroid gland, tachycardia, reduction of body weight, increase in intensity standard metabolism (see). At contact with skin of salt C. cause emergence of slowly healing burns (see) and resistant dermatitis (see). At hit on skin of Se dioxide there is a sharp morbidity, numbness, rashes.

At acute poisonings with connections C. note irritation of mucous membranes of upper respiratory tracts and a conjunctiva, dry cough, allocations from a nose, the general weakness, a headache, nausea, vomiting, off-flavor in a mouth. The garlick smell of expired air is characteristic. Sometimes there comes the loss of consciousness, a collapse. Especially hard acute poisoning with hydrogen selenide proceeds, at Krom severe damages of a liver and kidneys are possible a fluid lungs (see), development of pneumonia (see).

First aid and emergency treatment

the Victim needs to be brought to the warm, aired placement or on fresh air, eyes to wash out 2% solution of Natrii hydrocarbonas, the same solution to rinse a throat, in a nose to dig 2% solution of ephedrine, to intramusculary enter 1 ml of 1% of solution of Dimedrol or 2,5% of solution of Pipolphenum, to inside give codeine. At a loss of consciousness or a collapse to enter under skin 1 ml of 0,1% of solution of strychnine, intravenously 1 ml of 0,06% of solution of Korglykonum, 1 ml of 1% of solution of a phenylephine hydrochloride into 200 — 300 ml of 5% of solution of glucose or isotonic solution of sodium chloride (kapelno). At spasms vitamin of Vkh, 5 — 10 ml of 25% of solution of magnesium sulfate intramusculary is shown. At a toxic fluid lungs recommend long inhalation of the moistened oxygen, intravenously 20 ml of 40% of solution of glucose from 500 mg ascorbic to - you, bronchodilators: an Euphyllinum (provided that there is no decrease in the ABP), ephedrine; at an apnoea — lobeline or Cytitonum. The victim needs to provide rest, heat. At hron. S.'s intoxications and its connections symptomatic treatment.

Measures of prevention of poisonings with selenium, hydrogen selenide, Se dioxide and other connections C. consist in improvement tekhiol. processes on the corresponding productions, sealing of the equipment and its maximum mechanization. Careful protection of a respiratory organs by means of industrial gas masks (see) and respirators is necessary (see) and skin by means of overalls and rubber gloves, and also observance of measures of personal hygiene: washing of hands, the general shower and change of linen after work, prohibition of smoking and acceptance of food in production rooms.

The persons contacting to S. and its connections shall have medical examination (see) at employment and annually. Special attention needs to be paid on a condition of a respiratory organs, c. N of page, parenchymatous bodies, conjunctivas and skin. Important preventive value has a diet, to-ry shall be protein-rich also carbohydrates. Women on all duration of gestation from the date of her establishment and for feeding are exempted from work, on a cut they contact to S.; they are transferred to other sites.

The large role in prevention of poisonings is played by the organization a dignity. control of S.'s maintenance and its connections in air of production rooms.

Maximum allowable concentrations for elementary selenium — 2 mg/m 3 , for Se dioxide — 0,1 mg/m3, hydrogen selenide — apprx. 0,1 mg/m3.

Selenium in the medicolegal relation

At a research of a corpse in case of S.'s poisoning which was quickly caused death or its connections from internals is felt a characteristic smell of garlic, mucous membranes of a trachea, bodies went. - kish. a path, kidneys and a liver are painted in pinkish-orange color. At approach of death in later terms after hit in an organism With. this coloring can be expressed poorly or be absent absolutely. Histologically dystrophic changes in a myocardium, a liver and kidneys come to light.

Court. - chemical definition of S. make after a mineralization of cadaveric material during the heating with concentrated sulfuric and nitric to-tami, by S.'s recovery or on reactions with 3,3-diaminoben-zidinom, vismutoly II, dithizon. Carrying out reactions of recovery and with 3,3 diaminobenzidine allows to otdifferentsirovat S. from tellurium. Sensitivity of staining reactions makes 1 — 2 mkg, reactions of recovery — 10 mkg. Quantitatively S. at court. - chemical researches determine by a photometric method by reaction with dithizon.



Bibliography: Brakhnova I. T. Toxicity of powders of metals and their connections, page 136, Kiev, 1971; Harmful substances in the industry, under the editorship of N. V. Lazarev and I. D. Gadaskina, t. 3, page 75, JI., 1977; Glinka N. L. General chemistry, page 373, etc., M., 1978; And z r and e l - with about N 3. And., Mogilev O. Ya. and Suvorov S. V. Questions of occupational health and professional pathology during the work with rare metals, page 245, M., 1973; Krylova A. N. and Rubtsov A. F. Definition of selenium in biological material by a ditizonatny method, Court. - medical examination, t. 17, No. 1, page 41, 1974; Levin V. I. Receiving radioisotopes, M., 1972; N e-nitsesku To. The general chemistry, the lane from Romanians., page 392, M., 1968; Table of isotopes, ed. by C. M. Lederer a. V. S. Shirley, N. Y., 1978.


H. G. Budkovskaya; V. V. Bochkaryov (I am glad.), A. F. Rubtsov (court.), N. Yu. Tarasenko (gigabyte. work).

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