Arsenic to which family applies. Arsenic is a dangerous but necessary substance. Finding in the nature of arsenic

Finding in the nature of arsenic

Get arsenic

Arsenic application

• The use of arsenic in metallurgy - is used to dop the lead alloys going to prepare the fraction, since when casting a fraction with a tower method, a mysterious alloy with lead acquire a strictly spherical shape, and in addition, the strength and solidity of the lead increase.
• Application in electrical engineering - arsenic of particular purity (99.9999%) is used to synthesize a number of practically very valuable and important semiconductor materials - arsenides and complex diamond-like semiconductors.
• Application as a dye - arsenic sulphide compounds - aurapygment and realgar - used in painting in quality paints.
• Application in the leather industry - used as a means to remove hair with leather.
• Application in pyrotechnics - realgar is used to obtain "Greek", or "Indian", fire arising from burning a mixture of Realgar with gray and Selitra (bright white flame).
• Application in medicine - Many of the arsenic compounds in very small doses are used as drugs to combat anemia and a number of serious diseases, as they have a clinically significant stimulating effect on a number of functions of the body, in particular, to bleeding. From the inorganic compounds of arsenic arsenic anhydride can be used in medicine for the preparation of pill and in dental practice in the form of pasta as a necrotic drug (the very "arsenic", which is laying in a tooth channel before removing the nerve and sealing). Currently, arsenic drugs are used in dental practice rarely due to toxicity and the possibility of making painless tooth denervation under local anesthesia.
• Application in glass production - arsenic trioxide makes the glass "deaf", i.e. opaque. However, small additives of this substance, on the contrary, brighten the glass. Arsenic and now enters the recipes of some glasses, for example, the "Vienna" glass for thermometers and twist.

The most promising area of \u200b\u200bthe use of arsenic, undoubtedly semiconductor technique. Of particular importance was the ARSENIDES GALLY GAAS and India Inas. Arsenide Gallium is also needed for an important direction of electronic equipment - optoelectronics, which arose in 1963 ... 1965. At the junction of physics solid, optics and electronics. The same material helped create the first semiconductor lasers.

Why did the arsenids prosesented for semiconductor technology? To answer this question, we remind briefly about some of the basic concepts of semiconductor physics: "valence zone", "prohibited zone" and "conduction zone".

Unlike a free electron, which can possess any energy, an electron, enclosed in an atom, can only have some, well-defined energy values. Of the possible values \u200b\u200bof electron energy in the atom there are energy zones. By virtue of the well-known principle of Pauli, the number of electrons in each zone cannot be more than a certain maximum. If the zone is empty, then it naturally cannot participate in the creation of conductivity. Do not participate in conductivity and electrons entirely filled zone: since there are no free levels, the external electric field cannot cause the electron redistribution and thereby create an electric current. Conductivity is possible only in a partially filled zone. Therefore, the bodies with a partially filled zone belong to metals, and bodies in which the energy spectrum of electronic states consists of filled and empty zones - to dielectrics or semiconductors.

Recall also that the entire zones in crystals are called valence zones, partially filled with and empty - conduction zones, and the energy interval (or barrier) between them is a prohibited zone.

The main difference between dielectrics and semiconductors is precisely in the width of the prohibited zone: if it needs more than 3 eV to overcome it, then crystal refers to dielectrics, and if less - to semiconductors.

Compared to classical semiconductors of the IV group - Germany and silicon - the arsenides of elements of the Group III have two advantages. The width of the forbidden zone and the mobility of charge carriers in them can be varied in broader limits. And the more movable charge carriers, the semiconductor device can work at high frequencies. The width of the forbidden zone is chosen depending on the appointment of the device.

Thus, for rectifiers and amplifiers designed to work at elevated temperatures, a material with a large width of the forbidden zone is used, and for cooled infrared radiation receivers - with small.

Arsenide Galli has acquired a special popularity because he has good electrical characteristicswhich it retains in a wide temperature range - from minus to plus 500 ° C. For comparison, we indicate that India Arsenide, not inferior to GaAs electric properties, starts to lose them already room temperature, Germany - at 70 ... 80, and silicon - at 150 ... 200 ° C.

Arsenic is used as a doping additive, which gives "classic" semiconductors (Si, GE) a conductivity of a certain type. In this case, the so-called transition layer is created in the semiconductor, and, depending on the purpose of the crystal, it is doped so as to obtain a transition layer at different depths. In crystals intended for the manufacture of diodes, its "hiding" deeper; If the semiconductor crystals will do solar panels, then the depth of the transition layer is not more than one micrometer.

Arsenic as a valuable additive is used in non-ferrous metallurgy. Thus, the additive to the lead 0.2 ... 1% AS significantly increases its hardness. The fraction, for example, is always done from lead, doped with arsenic - otherwise not to get a strictly spherical shape of crushers.

Supplement 0.15 ... 0.45% of arsenic in copper increases its tensile strength, hardness and corrosion resistance when working in a rolled medium. In addition, arsenic increases copper fluidity during casting, facilitates the process of wire dragging.

Add arsenic into some varieties of bronze, brass, babbitis, typographic alloys.

And at the same time, arsenic very often harms metallurgists. In the production of steel and many non-ferrous metals, intentionally go to the complication of the process - just to remove all arsenic from metal. The presence of arsenic in ore makes the production of harmful. Harmful twice: first, for people's health; Secondly, for metal - significant impurities of arsenic worsen the properties of almost all metals and alloys.

All compound. arsenic, r-role in water and weakness media (eg, gastric juice), extremely poisonous; MPC in the air arsenic and its comprehensive. (except ash3) in terms of arsenic 0.5 mg / m3. Seda. AS (III) more poisonous than compound. AS (V). From noorg. Seda. AS2O3 and ASH3 are especially dangerous. When working with arsenic and its social. Needed: full sealing of equipment, removal of dust and gases intense ventilation, compliance with personal hygiene (anti-high clothing, glasses, gloves, gas masks), frequent medical control; Women and adolescents are not allowed to work. In acute poisoning, arsenic observed vomiting, abdominal pain, diarrhea, oppression center. nervous system. Help and antidote in arsenic poisoning: Reception of aquatic p-mms Na2S2O3, washing the stomach, reception of milk and cottage cheese; Specific. Antidote - Unitiol. A special problem is to remove arsenic from outgoing gases, tehnol. Waters and side products of processing ores and concentrates of non-ferrous and rare metals and iron. Naib The method of burial arsenic is promising by translating it into almost insoluble sulfide glass.

Arsenic is famous with deep antiquity. An Aristotle mentioned his priest. Survy connections. It is not known who first received elementary arsenic, usually this achievement is attributed to Albert Great Ok. 1250. Chem. The element of arsenic is recognized by A. Lavoisier in 1789.

Such is the element No. 33 deservedly enjoyed by a bad reputation, and yet in many cases very useful.

The content of arsenic in the earth's crust is only 0.0005%, but this element is quite active, and therefore minerals, which includes arsenic, over 120. The main industrial mineral of arsenic - Arsenopyritis Feass. Large copper-arsenic fields are in the USA, Sweden, Norway and Japan, arsenic-cobalt - in Canada, arsenic-tin - in Bolivia and England. In addition, golden-ryyaky deposits in the USA and France are known. Russia has numerous arsenic fields in Yakutia and the Caucasus, in Central Asia and in the Urals, in Siberia and in Chukotka, in Kazakhstan and in Transbaikalia. Arsenic is one of the few items, the demand for which is less than the possibility of their production. World arsenic (without socialist. Countries) in terms of AS2O3 approx. 50 thousand tons (1983); Of these, ~ 11 tons of elementary arsenic of particular purity for the synthesis of semiconductor compounds are obtained.

The x-ray fluorescent method of analyzing arsenic is quite simple and safe, unlike the chemical method. A pure ball is pressed into the tablet and is used as a standard. GOST 1293.4-83, GOST 1367.1-83, GOST 1429.10-77, GOST 2082.5-81, GOST 2604.11-85, GOST 6689.13-92, GOST 11739.14-99 Definition is performed using a X-ray fluorescent spectrometer. The most proven in this area is the EDX 3600 B and EDX 600 spectrometers.

The content of the article

ARSENIC- The chemical element of the group V of the periodic table refers to the nitrogen family. Relative atomic weight 74,9216. In nature, arsenic is represented by only one stable nuclide 75 AS. More than ten of his radioactive isotopes With a half-life from a few minutes to several months. Typical oxidation degrees in connections -3, +3, +5. The name of arsenic in Russian is associated with the use of its compounds for the extermination of mice and rats; latin name Arsenicum comes from the Greek "Arsen" - strong, powerful.

Historical information.

Arsenic refers to the five "alchemical" elements, open in the Middle Ages (surprisingly, but four of them are as, Sb, Bi and P are in one group of periodic table - fifth). At the same time, arsenic compounds were known since ancient times, they were used to produce paints and medicines. Especially interested in using arsenic in metallurgy.

A few thousand years ago, the stone age was replaced by bronze. Bronze is an alloy of copper with a tin. As historians believe, the first bronze was cast in the Tiger Valley and Euphrates, somewhere between 30 and 25 centuries. BC. In some regions, bronze was paid with particularly valuable properties - it was better than and washed easier. As modern scientists found out, it was an alloy of copper, containing from 1 to 7% arsenic and no more than 3% tin. Probably, at first, when it was smelted, Malachite was confused with a rich copper ore of Malachite with the weathered products of some too green sulfide copper-arsenic minerals. Assessing the wonderful properties of the alloy, the ancient craftsmen then specially searched for arsenic minerals. For searches, the property of such minerals was used when heated a specific garlic smell. However, over time, the smelting of arsenic bronze stopped. Most likely it happened due to frequent poisoning when firing arsenic-containing minerals.

Of course, arsenic was known in the distant past only in the form of his minerals. So, B. Ancient Chinam solid realgar mineral (Sulfide of AS 4 S 4, Realgar in Arabic means "mineral dust") used for a stone thread, but when heated or in the light, it "spoiled", since it turned into AS 2 S 3. In 4 c. BC. Aristotle described this mineral called "Sandarak". In i century AD Roman writer and scholar of Pliny Senior, and the Roman doctor and nerd Diospuride described the mineral aurapygment (arsenic sulphide AS 2 S 3). Translated from Latin, the name of the mineral means "gold paint": it was used as a yellow dye. At 11 c. Alchemists distinguished three "varieties" of arsenic: the so-called white arsenic (AS 2 O 3 oxide), yellow arsenic (AS 2 S sulfide) and a red arsenic (AS 4 s 4 sulfide). White arsenic was obtained when the impurities of arsenic impurities under the firing of copper ores containing this element. Condensing from the gas phase, arsenic oxide saddled in the form white Nalea. White arsenic used since ancient times to destroy pests, as well as ...

At 13th century Albert von Troll (Albert Great) received a metal-like substance, heating yellow arsenic with soap; Perhaps it was the first sample of arsenic in the form of a simple substance obtained artificially. But this substance violated a mystical "connection" of seven known metals with seven planets; Probably, therefore, alchemists considered arsenic "illegitimate metal". At the same time, they discovered his property to give copper white colorthat gave the reason to call him "a means whitening Venus (i.e. copper)".

Arsenic was definitely identified as an individual substance in the middle of the 17th century, when the German pharmacist Johann Schröder received it in a relatively clean form of the reduction of oxide wood coal. Later, the French chemist and the doctor Nicola Lemer got arsenic, heating the mixture of its oxide with soap and sweat. In 18 V. The arsenic was already well known as an unusual "semimetal". In 1775, Swedish chemist K.V. Schemele received arsenic acid and gaseous arsenic hydrogen, and in 1789 A.L. Lavuaaze, finally, recognized arsenic with an independent chemical element. At 19 in. Organic compounds containing arsenic were opened.

Arsenic in nature.

In the earth's crust of arsenic - about 5 · 10 -4% (i.e. 5 g per ton), approximately as much as Germany, tin, molybdenum, tungsten or bromine. Often arsenic in minerals meets with iron, copper, cobalt, nickel.

The composition of minerals formed by arsenic (and they are known about 200), reflects the "semi-dollar" properties of this element, which may be both in positive and in a negative degree of oxidation and connect with many elements; In the first case, arsenic can play the role of metal (for example, in sulphides), in the second - non-metalla (for example, in arsenides). The complex composition of a series of arsenic minerals reflects its ability, on the one hand, to partially replace the sulfur and antimony atoms in the crystal lattice (ionic radii S -2, SB -3 and AS -3 are close and amount to 0.182, 0.208 and 0.191 nm), on the other - Metal atoms. In the first case, arsenic atoms are rather a negative degree of oxidation, in the second is positive.

The electronegativity of arsenic (2.0) is small, but higher than that of antimony (1.9) and in most metals, therefore the degree of oxidation -3 is observed for arsenic only in the arsenides of metals, as well as in the SBAs storchene and the fragments of this mineral with clean crystals antimony or arsenic (mineral allemontitis). Many compounds of arsenic with metals, judging by their composition, are more likely to intermetallic compounds, and not to arsenides; Some of them are distinguished by alternating arsenic content. Arsenide may be present at the same time several metals, the atoms of which, with a close radius of ions, replace each other in a crystal lattice in arbitrary ratios; In such cases, in the mineral formula, the symbols of elements are listed through commas. All acenetes have a metal shine, these are opaque, heavy minerals, their hardness is small.

An example of natural agenides (they are known about 25) can serve minerals Leilllingite Feas 2 (Analog Pyrite Fes 2), SkortTerrite COAS 2-3 and Nickelskutterite NIAS 2-3, Nickelin (Red Nickel Qucheredan) Nias, Rammelsbergit (White Nickel Qucheredan) Nias 2 , Sufflorite (Spese cobalt) COAS 2 and KLINOS Acaffloit (CO, FE, NI) AS 2, LANGISIT (CO, NI) AS, Spearlit PTAS 2, Majereite Ni 11 AS 8, Oregonite Ni 2 Feas 2, Alto Cu 6 AS. Due to high density (more than 7 g / cm 3), many of them geologists belong to the group "superheavy" minerals.

The most common mineral of arsenic - Arsenopyritis (Arsenic Qucheredan) FeasS can be viewed as a sulfur replacement product in Fes 2 arsenic atoms (in conventional pyrite, there are also a little arsenic). Such compounds are called sulfosols. The minerals of Cobaltin (cobalt shine) Coass, Glauceodot (CO, FE) Ass, Hersdorfit (Nickel Glitter) of Niass, Enargit and LuConitis of the same composition, but of various buildings of Cu 3 ASS 4, AG 3 ASS 3 is an important silver ore, which is an important silver ore Sometimes called "ruby silver" due to bright red, it is often found in the upper layers of silver lived, where the magnificent large crystals of this mineral were found. Sulfosoli may contain noble metals platinum group; These are minerals OSARSIT (OS, RU) ASS, RUARSIT RUASS, IRARCIT (IR, RU, RH, PT) Ass, Platarsit (PT, RH, RU) Ass, Holling (RD, PT, PD) ASS. Sometimes the role of sulfur atoms in such double arsenides play antimony atoms, for example, in Seinaiokita (Fe, Ni) (SB, AS) 2, Arsenopallade PD 8 (AS, SB) 3, Arsenopolybazitis (AG, CU) 16 (AR, SB) 2 S 11.

Interestingly, the structure of minerals in which arsenic is present simultaneously with sulfur, but plays the role of metal, grouped together with other metals. These are Minerals Arsenosulvanit Cu 3 (AS, V) S 4, Arsenogochorekornitis Ni 9 Biass 8, Freibergitis (AG, CU, FE) 12 (SB, AS) 4 S 13, Tetnutite (CU, FE) 12 AS 4 S 13, Argentotennant (AG, CU) 10 (Zn, Fe) 2 (AS, SB) 4 S 13, Goldfiltite CU 12 (TE, SB, AS) 4 S 13, Loins (CU, ZN, AG) 12 (AS, SB) 4 (SE, S) 13. It can be imagined which complex structure has a crystal lattice of all these minerals.

An unequivocally positive degree of oxidation of arsenic has in natural sulphides - Yellow Auripigiment AS 2 S 3, orange-yellow AS 4 S 3 dimension, orange-red Realgar AS 4 S 4, carmine-red hetchellite ASSBS 3, as well as in colorless AS 2 O oxide 3, which is found in the form of the minerals of arsenolite and clallite with a different crystal structure (they are formed as a result of the weathelation of other arsenic minerals). Usually these minerals are found in the form of small inclusions. But in the 30s 20 century. In the southern part of the Verkhoyansky ridge, huge auripigression crystals of up to 60 cm and a weight of up to 30 kg were found.

In natural arsenic acid salts H 3 ASO 4 - arsenates (about 90), the degree of oxidation of arsenic is +5; An example is the bright pink eryitrine (cobalt color) CO 3 (ASO 4) 2 · 8H 2 O, green Anabergite Ni 3 (ASO 4) 2 · 8H 2 O, rains FE III ASO 4 · 2H 2 O and FE Symplizit 3 (ASO 4) 2 · 8H 2 O, Buro-Red Gasparite (CE, LA, ND) ARO 4, Colorless Gurns MG 3 (ASO 4) 2 · 8H 2 O, Rooseveltitis Biaso 4 and Kettigit Zn 3 (ASO 4) 2 · 8H 2 O, as well as a plurality of basic salts, for example, Cu 2 ASO 4 (OH) olivenitis, Arsenobismite Bi 2 (ASO 4) (OH) 3. But natural arsenites - the derivatives of arsenic acid H 3 ASO 3 are very rare.

In Central Sweden, there are famous Langban iron-manganese careers, which found and described more than 50 samples of minerals, which are arsenates. Some of them are no longer found anywhere. They were formed sometime as a result of the reaction of arsenic acid H 3 ASO 4 with Mn (OH) 2 pyrocroit at not very high temperatures. Usually arsenates - sulfide ore oxidation products. They, as a rule, do not have industrial applications, but some of them are very beautiful and decorated with mineralogical collections.

In the names of numerous arsenic minerals, you can meet toponyms (Lilling in Austria, Freiberg in Saxony, Seinaioki in Finland, Skortterud in Norway, Allemon in France, Canadian Rudnik Langis and Hetchell mine in Nevada, Oregon in the USA, etc.), geologists, names, chemists, political figures, etc. (German chemist Karl Rammelsberg, Munich Mineral Merchant William Muhher, owner of Mine Johann von Hersdorf, French chemist F.Kodé, English Chemists John Prost and Smithson Tennant, Canadian Chemist F. L. Sverri, US President Roosevelt, etc.), Plant Names (So, the name of the mineral of Sufflorite occurred from Saffran), the initial letters of the names of elements - arsenic, osmia, ruthenium, iridium, palladium, platinum, Greek roots ("Eritros" - red, "Enargon" - visible, "Lithos" - stone) and etc. etc.

Interestingly, the old name of the Nickeline mineral (NIAS) is Cuppernikel. Medieval German miners called Nickel of the Evil Mountain Spirit, and Kupfernickel, from him. Kupfer - Copper) - "Damn Copper", "Fake Copper". Copper-red crystals of this ore externally looked like a copper ore; It was used in glassware for staining glass in green. But the copper from it could not get anyone. This ore in 1751 was investigated by Swedish mineralogs Axel Krasctedt and allocated a new metal from it, calling it nickel.

As arsenic is chemically enough inert, it is found in native state - in the form of surrounding needles or cubes. Such arsenic usually contains from 2 to 16% impurities - most often it is SB, BI, AG, FE, NI, CO. It is easy to confuse into powder. In Russia, native arsenic geologists found in Transbaikalia, in the Amur region, it is found in other countries.

The arsenic is unique in that it is found everywhere - in minerals, rocks, soil, water, plants and animals, it is not for nothing that it is called "omnipresent". The distribution of arsenic in various regions of the globe was largely determined in the process of forming a lithosphere of the volatility of its compounds at high temperature, as well as sorption and desorption processes in soils and sedimentary rocks. Arsenic easily migrates, which contributes to a sufficiently high solubility of some of its compounds in water. In the humid climate, arsenic is washed out of the soil and carries ground waters, and then rivers. The average of arsenic content in rivers - 3 μg / l, in surface waters - about 10 μg / l, in the water of the seas and oceans - only about 1 μg / l. This is explained by the relatively rapid precipitation of its compounds from water with accumulation in bottom sediments, for example, in iron orders.

In soils, the content of arsenic is usually from 0.1 to 40 mg / kg. But in the area of \u200b\u200barising arsenic ores, as well as in volcanic areas in the soil, there may be a lot of arsenic - up to 8 g / kg, as in some areas of Switzerland and New Zealand. In such places, vegetation die, and animals are sick. This is characteristic of steppes and deserts, where arsenic is not washed out of the soil. Enriched compared to the average content and clay rocks - they contain four of them more arsenic than an average. In our country, 2 mg / kg is considered the maximum permissible concentration of arsenic in the soil.

Arsenic can be carried out of the soil not only with water, but also by the wind. But for this, he must first turn into volatile arsenaganic connections. Such a transformation occurs as a result of the so-called biometylation - the connection of the methyl group with the formation of C-AS communication; This enzymatic process (it is well known for mercury compounds) occurs with the participation of the coenzyment of methylkobalamina - methylated derivative of vitamin B 12 (it is also in the human body). Arsenic biometylation occurs both in fresh and in sea water and leads to the formation of arsenaganic compounds - methylarsonic acid CH 3 ASO (OH) 2, dimethylarsin (Dimethylsian, or kaocodile acid (CH 3) 2 AS (O) OH, trimethylarsina ( CH 3) 3 AS and its oxide (CH 3) 3 as \u003d o, which are also found in nature. Using 14 C-labeled methylcobalamina and 74 AS-labeled sodium hydroacenate Na 2 Haso 4, it was shown that one of the strains of methanobacteria restores and methylates this salt to volatile dimethylarsin. As a result, rural areas contain an average of 0.001 - 0.01 μg / m 3 of arsenic, in cities where there are no specific contaminants - up to 0.03 μg / m 3, and near the sources of pollution (plants for non-ferrous metals, power plants, power plants, Working on the corner with a high arsenic content, etc.) The concentration of arsenic in the air may exceed 1 μg / m 3. The intensity of the loss of arsenic in the location of industrial centers is 40 kg / km 2 per year.

The formation of volatile arsenic compounds (trimethylarsin, for example, boils only at 51 ° C) caused 19 V. Numerous poisoning, as arsenic was kept in plaster and even in green paint for wallpaper. In the form of paint used to use the greens of Cu 3 (ASO 3) 2 · n.H 2 O and Paris, or Schiafurty Cu 4 (ASO 2) 6 (CH 3 COO) 2. Under the conditions of high humidity and the appearance of mold from such paint, volatile arsenaganic derivatives are formed. It is assumed that this process could cause slow poisoning of Napoleon in the last years of his life (as you know, arsenic was found in Napoleon's hair after a century after his death).

Arsenic in noticeable quantities is contained in some mineral waters. Russian standards establish that in the medical and table mineral waters of arsenic should be no more than 700 μg / l. IN Jermuk It may be several times more. Twisted one or two glasses of "arsenic" mineral water to man harm will not bring: to me to poison themselves, you need to drink at once liters of three hundred ... But it is clear that such water can not be drunk constantly instead of ordinary water.

Chemists found out that arsenic in natural waters can be in different forms, which is essential from the point of view of its analysis, methods of migration, as well as the different toxicity of these compounds; So, the compounds of trivalent arsenic are 25-60 times toxic than the five-time. The compounds of AS (III) in water are usually present in the form of weak arsenic acid H 3 ASO 3 ( rK. a \u003d 9.22), and compounds AS (V) - in the form of a significantly stronger arsenic acid H 3 ASO 4 ( rK. A \u003d 2.20) and its depotonated anions H 2 ASO 4 - and HASO 4 2-.

In the living substance arsenic on average contains 6 · 10 -6%, that is, 6 μg / kg. Some seaweed are capable of concentrating arsenic to such an extent that they become dangerous for people. Moreover, these algae can grow and multiply in pure solutions of arsenic acid. Such algae are used in some Asian countries as a means against rats. Even in the pure waters of Norwegian fjords, algae may contain arsenic in an amount of up to 0.1 g / kg. A person has arsenic in brain fabric and in the muscles, it accumulates in hair and nails.

Properties of arsenic.

Although arsenic looks like a metal, it is still nonmetal: it does not form salts, for example, with sulfuric acid, but itself is an acid-forming element. Therefore, this element is often called semimetal. Arsenic exists in several allotropic forms and in this regard very reminds phosphorus. The most resistant one is gray arsenic, a very fragile substance that has a metal glitter in a fresh break (hence the name "Metal arsenic"); Its density is 5.78 g / cm 3. With strong heating (up to 615 ° C), it is removed without melting (the same behavior is characteristic of the iodine). Under the pressure of 3.7 MPa (37 atm) arsenic melts at 817 ° C, which is significantly higher than the reaches. The electrical conductivity of gray arsenic is 17 times less than in copper, but 3.6 times higher than that of mercury. With increasing temperature, its electrical conductivity, as in typical metals, is reduced to about the same degree as in copper.

If the arsenic couples very quickly cool to the temperature of the liquid nitrogen (-196 ° C), the transparent soft substance is obtained, resembling the yellow phosphorus, its density (2.03 g / cm 3) is significantly lower than that of gray arsenic. Arsenic and yellow arsenic pairs consist of AS 4 molecules having a tetrahedron shape - and here analogy with phosphorus. At 800 ° C, a noticeable dissociation of vapors begins with the formation of AS 2 dimers, and only AS 2 molecules remain at 1700 ° C. When heated and under the action of ultraviolet, yellow arsenic quickly goes into gray with heat release. When condensation of arsenic vapor in an inert atmosphere, another amorphous form of this black element is formed. If the arsenic pairs are precipitated on the glass, a mirror film is formed.

The structure of the external electron shell in arsenic is the same as Nitrogen and Phosphorus, but unlike them, he has 18 electrons on the penultimate shell. As well as phosphorus, it can form three covalent bonds (configuration 4S 2 4P 3), and a recalculated steam remains on the AS atom. The charge sign on the AS atom in compounds with covalent bonds depends on the electronegativity of neighboring atoms. The participation of the conductive pair in complexation for arsenic is significantly difficult compared to nitrogen and phosphorus.

If D-orbital is involved in the AS atom, it is possible to break 4S-electrons to form five covalent bonds. This possibility is practically carried out only in a compound with fluorine - in the ASF 5 pentafluoride (known and pentachloride ASCL 5, but it is extremely distexts and quickly decomposes even at -50 ° C).

In the dry air, arsenic is stable, but in a wet dirty and covered with black oxide. When the pair of arsenic is easily burned in the air with a blue flame with the formation of heavy white vapors of arsenic anhydride AS 2 O 3. This oxide is one of the most common musicals-containing reagents. It has amphoteric properties:

AS 2 O 3 + 6HCl ® 2AsCl 3 + 3H 2 O,

2 O 3 + 6NH 4 OH ® 2 (NH 4) 3 ASO 3 + 3H 2 O.

When oxidizing AS 2 O 3, acidic oxide is formed - arsenic anhydride:

AS 2 O 3 + 2HNO 3 ® AS 2 O 5 + H 2 O + NO 2 + NO.

With its interaction with soda, sodium hydroacente is obtained, which is used in medicine:

AS 2 O 3 + 2NA 2 CO 3 + H 2 O ® 2NA 2 HASO 4 + 2CO 2.

Clean arsenic is quite inert; Water, alkalis and acids that do not have oxidative properties, do not act on it. Dilute nitric acid oxidizes it to orthomyshydic acid H 3 ASO 3, and concentrated - to orthomyshycoa H 3 ASO 4:

3as + 5hno 3 + 2H 2 O ® 3H 3 ASO 4 + 5NO.

Arsenic oxide (III) reacts similarly:

3as 2 O 3 + 4HNO 3 + 7H 2 O ® 6H 3 ASO 4 + 4NO.

Arsenic acid is an acid of medium power, slightly weaker phosphorus. Unlike her, arsenic acid is very weak, according to its strength corresponding to boric acid H 3 BO 3. In its solutions there is an equilibrium H 3 ASO 3 HASO 2 + H 2 O. Arsenic acid and its salts (arsenites) - strong reducing agents:

Haso 2 + i 2 + 2H 2 O ® H 3 ASO 4 + 2HI.

Arsenic reacts with halogens and gray. ASCL 3 chloride - colorless oily liquid, smoking in air; Water hydrolyzed: ASCL 3 + 2H 2 O ® HASO 2 + 3HCl. ASBR 3 bromide and ASI 3 iodide, which are also decomposed by water are known. In the arsenic reactions with sulfur, sulphides of various composition are formed - right up to AR 2 S 5. Arsenic sulphides dissolve in alkalis, in a solution of ammonium sulfide and in concentrated nitric acid, for example:

AS 2 S 3 + 6KOH ® K 3 ASO 3 + K 3 ASS 3 + 3H 2 O,

2 S 3 + 3 (NH 4) 2 S ® 2 (NH 4) 3 ASS 3,

2 S 5 + 3 (NH 4) 2 S ® 2 (NH 4) 3 ASS 4,

AS 2 S 5 + 40HNO 3 + 4H 2 O ® 6H 2 ASO 4 + 15H 2 SO 4 + 40NO.

Tioarsenites and thioarsenates are formed in these reactions - the salts of the corresponding thiocoslons (similar to thioseric acid).

In the reaction of arsenic with active metals, saline arsenids are formed, which are hydrolyzed by water especially quickly the reaction in an acidic environment with the formation of an Arsin: Ca 3 AS 2 + 6HCl ® 3CaCl 2 + 2ash 3. Arsenids of low-effective metals - GaAs, Inas, etc. have a diamond-like atomic grille. Arsin is a colorless very poisonous gas without smell, but the impurities give him the smell of garlic. Arsin is slowly decomposed on the elements at room temperature and quickly - when heated.

Arsenic forms many arsenaganic compounds, for example, tetramethyldaarsin (CH 3) 2 AS-AS (CH 3) 2. Another 1760, director of the Servian Porcelain Factory Louis Claude Cada de Gassicur, distilling potassium acetate with arsenic oxide (III), unexpectedly received a smoking liquid with a disgusting smell, which was called alarcin, or liquid. As they found out later, in this fluid, first obtained organic derivatives of arsenic were contained: the so-called oxide asked, which was formed as a result of the reaction

4CH 3 Cook + AS 2 O 3 ® (CH 3) 2 AS-O-AS (CH 3) 2 + 2K 2 CO 3 + 2CO 2, and Dicacodyl (CH 3) 2 AS-AS (CH 3) 2. I like (from Greek. "Kakos" - bad) was one of the first radicals opened in organic compounds.

In 1854, the Paris professor of Chemistry of Auguste Kaur synthesized trimethylarsin by the action of methylodide on sodium arsenide: 3ch 3 I + ASNA 3 ® (CH 3) 3 AS + 3NAI.

In the subsequent syntheses used arsenic trichloride, for example,

(CH 3) 2 Zn + 2AsCl 3 ® 2 (CH 3) 3 AS + 3ZNCl 2.

In 1882, aromatic arsins were obtained by the action of a metallic sodium on a mixture of aryl halides and arsenic trichloride: 3C 6 H 5 CL + ASCL 3 + 6NA ® (C 6 H 5) 3 AS + 6NACL. The most intensively chemistry of organic arsenic derivatives developed in the 20s of the 20th century, when some of them were detected antimicrobial, as well as an irritant and skin-disruptive effect. Currently, tens of thousands of muscularial compounds are synthesized.

Get arsenic.

Arsenic is obtained mainly as a byproduct of processing copper, lead, zinc and cobalt ores, as well as in gold mining. Some polymetallic ores contain up to 12% of arsenic. When you heated such ores up to 650-700 ° C in the absence of air, arsenic is removed, and when heated in air is formed by flying oxide AS 2 O 3 - "White arsenic". It is condensed and heated with coal, while arsenic recovery occurs. Getting arsenic - harmful production. Previously, when the word "ecology" was known only to narrow specialists, "White arsenic" was released into the atmosphere, and he was sown in the neighboring fields and forests. In exhaust gases of arsenic plants, contains from 20 to 250 mg / m 3 AS 2 O 3, while usually in the air contains approximately 0.00001mg / m 3. The average daily permissible concentration of arsenic in the air is only 0.003 mg / m 3. Paradoxically, but now much more polluting the environment with arsenic not plants in its production, but non-ferrous metallurgy enterprises, burning stone coal. In bottom sediments near the copperlavyl plants, a huge amount of arsenic is contained - up to 10 g / kg. Arsenic can get into the soil and with phosphoric fertilizers.

And one more paradox: get arsenic more than it is required; This is a rather rare case. In Sweden, "unnecessary" arsenic were forced to even be styling in reinforced concrete containers in deep abandoned mines.

Main Industrial Mineral Arsenic - Arsenopyritis Feass. Large copper-arsenic fields are in Georgia, Central Asia and Kazakhstan, in the United States, Sweden, Norway and Japan, arsenic-cobalt - in Canada, arsenic-tin - in Bolivia and England. In addition, gold-arsenic deposits in the United States and France are known. Russia has numerous mysteria deposits in Yakutia, in the Urals, in Siberia, Transbaikalia and Chukotka.

Definition of arsenic.

A high-quality response to arsenic is the deposition of the yellow Sulfide AS 2 S 3 of salt-sized solutions. Traces determine the march reaction or method of Guttsit: Paper strips, moistened with HGCL 2, are darked in the presence of an Arsin, which restores the proportion to mercury.

In recent decades, various sensitive methods of analysis have been developed, with which you can quantify the insignificant concentrations of arsenic, for example, in natural waters. Among them, fiery atomic absorption spectrometry, atomic emission spectrometry, mass spectrometry, atomic fluorescent spectrometry, neutron activation analysis ... If arsenic in water is very small, a preliminary concentration of samples may be required. Using such concentration, a group of Kharkiv scientists from the National Academy of Sciences of Ukraine has developed in 1999 an extraction-x-ray fluorescent method for determining arsenic (as well as Selena) in drinking water With sensitivity up to 2.5-5 μg / l.

For a separate definition of AS (III) and AS (V) compounds, they are pre-separated from each other with well-known extraction and chromatographic methods, as well as using selective hydrogenation. Extraction is usually carried out with the help of sodium dithiocarbamate or ammonium pyrrolidideinidiocarbamate. These compounds are formed with AS (III) insoluble complexes in water, which can be extracted with chloroform. Then, with the help of oxidation with nitric acid, arsenic can be translated into the aqueous phase. In the second sample, the arsenate into arsenitis is translated using a reducing agent, and then produce similar extraction. So define the "general arsenic", and then subtracting the first result from the second, the AS (III) and AS (V) are defined. If there are organic arsenic organic compounds in water, they are usually translated into the methyldarsin CH 3 ASI 2 or in dimetiliodarsyn (CH 3) 2 ASI, which are determined by one or another chromatographic method. So, with the help of highly efficient liquid chromatography, you can define nanogram amounts of the substance.

Many arsenic compounds can be analyzed by the so-called hydride method. It consists in selective restoration of the analyzed substance into the volatile ARSIN. Thus, inorganic arsenites are restored to ASH 3 at pH 5 - 7, and at pH

The neutron activation method is also sensitive. It lies in the irradiation of the neutron sample, while the nucleus 75 AS capture neutrons and turn into radionuclide 76 AS, which is detected by characteristic radioactivity with a half-life of 26 hours. So you can detect up to 10-10% arsenic in the sample, i.e. 1 mg per 1000 tons of substance

The use of arsenic.

About 97% of the mined arsenic is used in the form of its connections. Clean arsenic is rarely used. In the year all over the world, only a few hundred tons of metallic arsenic are obtained. In the amount of 3% arsenic improves the quality of bearing alloys. Arsenic additives to lead noticeably increase its hardness, which is used in the production of lead batteries and cables. Small arsenic additives increase corrosion resistance and improve the thermal properties of copper and brass. Arsenic high degree Purification is used in the production of semiconductor devices, in which it is fused with silicon or with Germany. Arsenic is used as a doping additive, which gives "classic" semiconductors (Si, GE) a conductivity of a certain type.

Arsenic as a valuable additive is used in non-ferrous metallurgy. Thus, the additive to the lead 0.2 ... 1% AS significantly increases its hardness. It has long been noticed that if you add a little arsenic in molten lead, then the fractions are obtained when the balls of correct spherical shape are obtained. Supplement 0.15 ... 0.45% of arsenic in copper increases its tensile strength, hardness and corrosion resistance when working in a rolled medium. In addition, arsenic increases copper fluidity during casting, facilitates the process of wire dragging. Add arsenic into some varieties of bronze, brass, babbitis, typographic alloys. And at the same time, arsenic very often harms metallurgists. In the production of steel and many non-ferrous metals, intentionally go to the complication of the process - just to remove all arsenic from metal. The presence of arsenic in ore makes the production of harmful. Harmful twice: first, for people's health; Secondly, for metal - significant impurities of arsenic worsen the properties of almost all metals and alloys.

Broader use have various connections Arsenic, which are produced annually tens of thousands of tons. AS 2 O 3 oxide is used in glass ward as a glass clarifier. Another ancient glassworms were known that white arsenic makes the glass "deaf", i.e. opaque. However, small additives of this substance, on the contrary, brighten the glass. Arsenic and now enters the formulation of some glasses, for example, the "Vienna" glass for thermometers.

Arsenic compounds are used as an antiseptic for protection against damage and preserving the skins, fur and stuffed, for the impregnation of wood, as the component of non-rigging paints for the bottoms of the courts. In this capacity, arsenic and arsenic acids are used: Na 2 Haso 4, Pbhaso 4, Ca 3 (ASO 3) 2 and others. The biological activity of the arsenic derivatives is interested in veterinarians, agronomists, Sansepid service specialists. As a result, arsenia-containing stimulants of growth and livestock productivity, anti-chemical means, drugs for the prevention of teen diseases on animals farms. Arsenic compounds (AS 2 O 3, CA 3 AS 2, Na 3 AS, Parisian Greens) are used to combat insects, rodents, as well as weeds. Previously, such an application was widespread, especially when processing fruit trees, tobacco and cotton plantations, to get rid of livestocks from lice and fleas, to stimulate growth in poultry and pig breeding, as well as for drying cotton before cleaning. In ancient China, the arsenic oxide treated rice crops to protect them from rats and fungal diseases and thus raise the crop. And in South Vietnam, American troops were used as a defoliant as a co-organic acid ("Agent Blue"). Now because of the poisonousness of the mysteria compounds, their use in agriculture limited.

Important areas of the use of arsenic compounds are the production of semiconductor materials and chips, fiber optics, cultivation of single crystals for lasers, film electronics. For the introduction of small strictly dosed quantities of this element in semiconductors, gaseous ARSIN is used. Gallium Arsenides Gaas and India INAS are used in the manufacture of diodes, transistors, lasers.

Limited application finds arsenic and medicine . The arsenic isotopes 72 AS, 74 AS and 76 AS are convenient for the studies of the half-life (26 hours, 17.8 days. And 26.3 hours, respectively) apply to the diagnosis of various diseases.

Ilya Leenson

Definition

Arsenic - Thirty-third element of the periodic table. Designation - AS from Latin "ARSENICUM". Located in the fourth period, VA group. Refers to semimetillands. The kernel charge is 33.

Arsenic occurs in nature mostly in compounds with metals or gray and only occasionally in a free state. The content of arsenic in the earth's crust is 0.0005%.

Usually arsenic is obtained from the FEASS's arsenic cchedan.

Atomic and molecular weight of arsenic

Relative molecular weight of the substance (M R) is a number indicating how many times the mass of this molecule is greater than 1/12 mass of the carbon atom, and relative atomic weight of the element (A R) - How many times the average mass of the atoms of the chemical element is greater than 1/12 mass of the carbon atom.

Since in the free state of arsenic exists in the form of single-name AS molecules, the values \u200b\u200bof its atomic and molecular masses coincide. They are 74,9216.

Allotropy and allotropic modifications of arsenic

Like phosphorus arsenic exists in the form of several allotropic forms. With quick cooling of steam (consisting of AS 4 molecules), a non-metallic fraction is formed - yellow arsenic (a density of 2.0 g / cm 3), isomorphic white phosphorus and is similar to it soluble in the servo-carbon. This modification is less stable than white phosphorus, and when lighting light or with weak heating, it easily goes into a metal modification - gray arsenic (Fig. 1). It forms a gray-steel fragile crystalline mass with a metal glitter in a fresh fond. The density is 5.75 g / cm 3. When heated under normal pressure, it is sublimated. It has metal electrical conductivity.

Fig. 1. Gray arsenic. Appearance.

Arsework isotopes

It is known that in nature arsenic may be in the form of a single stable isotope 75 AS. The mass number is 75, the atom core contains thirty-three proton and forty-two neutrons.

There are about 33 artificial not stable arsenic isotopes, as well as ten isomeric states of the cores, among which the most long-lived isotope 73 AS with a half-life equal to 80.3 days.

Arsenic ions

At the external energy level of arsenic atom there are five electrons that are valence:

1S 2 2S 2 2P 6 3S 2 3P 6 3D 10 4S 2 4P 3.

As a result of chemical interaction, arsenic gives his valence electrons, i.e. It is their donor, and turns into a positively charged ion:

AS 0 -3E → AS 3+;

AS 0 -5E → AS 5+.

Molecule and arsenic atom

In the free state of arsenic exists in the form of single-name AS molecules. We present some properties characterizing an atom and arsenic molecule:

Examples of solving problems

Example 1.

ARSENIC
As ARSENICUM),
The chemical element Va subgroups of the periodic system of elements belongs to the nitrogen family N, P, AS, SB, BI. Arsenic is most famous due to the use of it and its connections as a poison. In the ores occurs in the form of sulphides, arsenides, arsenites and arsenates. The most spread among the arsenic-containing minerals has arsenopyritis (arsenic verchestan) FeasS - the main raw material for receiving arsenic containing up to 46% AS. The leaders in the production of arsenic are France, Mexico, Sweden and the USA. The arsenic compounds are known from the ancient times, the earliest information is found in the works of the ancient Greek philosopher of the theofora (372-287 BC). The discovery of the element is usually attributed to Albert Great (Magnus, 1206-1280), the German philosopher and the author of the work on physics. In 1733, Brandt found that white arsenic in reality is arsenic oxide, and in 1817 Swedish chemist and minologist Y. Burtsellius determined the relative atomic mass of arsenic.
Properties and connections. Arsenic refers to nonmetallam, although from three allotropic modifications (yellow, black and metallic, or gray) gray is a crystalline mass with a metal gloss in a fresh break and, unlike other modifications, has a metal electrical conductivity. The gray form is most stable at room temperature and properties in the table are given for it. Properties of gray arsenic
Atomic number 33 atomic weight 74,9216 isotopes

stable 75.

unstable 70-74, 76-79, 81

The encyclopedia of the colley. - Open Society. 2000 .

Watch what is "arsenic" in other dictionaries:

ARSENIC - (ARSENUM, ARSENIUM, ARSENI CUM), solid metalloid, sim. AS; at. in. 74.96. In the periodic system of elements, it takes in order 33 E place, in 5 m row of V groups. Natural compounds M. with gray (Realgar and Auripigmentation) were still known in ... ... Big medical encyclopedia

ARSENIC - See arsenic (AS). As arsenic and its compounds are widely used in the national economy, it is contained in the wastewater of various industries of the metallurgical, chemical pharmaceutical, textile, glass, leather, chemical ... Fish diseases: Directory

Arsenic - (crude arsenic) is a solid extracted from natural arsenopyrites. It exists in two main forms: a) ordinary, so-called metallic arsenic, in the form of brilliant steel crystals, fragile, not ... Official terminology

- (symbol AS), poisonous semimetallic element of the fifth group of the periodic table; It was probably obtained in 1250 compounds containing arsenic, used as an invocoule for rodents, insects and as a means against weeds. They also apply ... Scientific and Technical Encyclopedic Dictionary

- (ARSENIUM), AS, chemical element V group of periodic system, atomic number 33, atomic weight 74,9216; Nonmetall gray, yellow or black, TPL 817 shc, is removed at 615 shc. Arsenic is used to obtain semiconductor ... ... Modern encyclopedia

Arsenic - (ARSENIUM), AS, chemical element V group of periodic system, atomic number 33, atomic weight 74,9216; Non-metal gray, yellow or black, TPL 817 ° C, is removed at 615 ° C. Arsenic is used to obtain semiconductor ... ... Illustrated Encyclopedic Dictionary

ARSENIC - Chem. Element, symbol AS (lat. Arsenicum), at. n. 33, at. m. 74.92; Nemmetal, exists in several allotropic modifications, density 5720 kg / m3. Under normal conditions, the most chemically racks are so-called metallic, or gray, arsenic. ... ... Large polytechnic encyclopedia

- (lat. Arsenicum) as, chemical element V group of periodic system, atomic number 33, atomic weight 74,9216. Russian name from the mouse (arsenic preparations were used to exterminate mice and rats). Forms several modifications. Ordinary arsenic ... Big Encyclopedic Dictionary

Arsenic, arsenic, mn. No, husband. one. Chemical element, solid, in large doses of a poisonous, usually part of different minerals, is supplied. For chemical, technical and medical purposes. 2. The preparation of this substance, prescribed by ... ... Explanatory Dictionary Ushakov

Arsenik (mind) Dictionary of Russian Synonyms. Arsenic SUT., Number of synonyms: 12 ARSENIC (2) ARSENICU ... Synonym dictionary

Arsenic (the name happened from the word mouse, was used to persuade mice) - thirty-third element of the periodic system. Refers to semimetillands. In a compound with acid, it does not forms salts, being an acid-forming substance. May form allotropic modifications. Arsenic has three famous crystal lattice structures today. Yellow arsenic shows the properties of a typical nonmetalla, amorphous - black and the most steady metallic, gray. In nature, most often occurs in the form of connections, less often - in a free state. The most common are arsenic compounds with metals (arsenides), such as: arsenic iron (arsenopyritis, poisonous pechestan), Nickelin (Kurfernikel, is named so because of its similarity with copper ore). Arsenic is an inactive element, insoluble in water, and its compounds relate to undermining substances. The oxidation of arsenic occurs during heating, at room temperature this reaction proceeds very slowly.

All arsenic compounds are very strong toxins that provide negative influence Not only at the gastrointestinal tract, but also on the nervous system. Stories are known many sensational cases of poisoning arsenic and its derivatives. The arsenic compounds were used as a poison not only in medieval France, they were still known in ancient Rome, Greece. The popularity of arsenic as a potent poison is explained by the fact that it is almost unrealistic to detect it in food, it does not have a smell or taste. When heated, turns into arsenic oxide. To diagnose arsenic poisoning is rather difficult, as it has similar symptoms with various diseases. Most often, arsenic poisoning is confused with cholera.

Where is arsenic applied?

Despite its toxicity, arsenic derivatives are used not only to escape mice and rats. Since pure arsenic has high electrical conductivity, it is used as a doping additive, which gives such semiconductors as Germany, silicon conductivity of the required type. In non-ferrous metallurgy, arsenic is used as a additive that gives alloys strength, hardness and corrosion resistance in the rolled medium. It adds it in small quantities to clarify the glass, in addition, it is part of the famous "Vienna Glass". Nickelin is used for glass color in green color. In the leather business, sulphate arsenic connections are used when processing the skins for removing hairs. Arsenic is part of varnishes and paints. In the woodworking industry use arsenic as an antiseptic. In pyrotechnics from the sulfide compounds of arsenic make "Greek fire" are used in the production of matches. Some arsenic compounds are used as combat poisoning substances. The toxic properties of arsenic are used in dental practice to kill the teeth pulp. In medicine, arsenic preparations are used as a medicine that increases the overall tone of the body, to stimulate an increase in the number of red blood cells. Arsenic has an inhibitory effect on the formation of leukocytes, so it is used in the treatment of some forms of leukemia. A huge amount of medical preparations created on the basis of arsenic is known, but recently less toxic drugs are gradually replaced.

Despite its toxicity, arsenic is one of the most necessary elements. When working with its compounds, it is necessary to adhere to the safety regulations, which will help to avoid unwanted consequences.