Physical properties of arsenic briefly. What is arsenic? Definition, formula, properties

Arsenic is a classic poison of medieval and modern poisoners
and medicine in modern sports and rehabilitation medicine
Toxic and poisonous stones and minerals

Arsenic(lat. Arsenicum), As, chemical element of group V of the periodic system of Mendeleev, atomic number 33, atomic mass 74.9216; steel-gray crystals. The element consists of one stable isotope 75 As. Poisonous in any form, medicine.

Historical reference.

Natural compounds of arsenic with sulfur (orpiment As 2 S 3, realgar As 4 S 4) were known to the peoples of the ancient world, who used these minerals as medicines and paints. The product of burning arsenic sulfides was also known - arsenic (III) oxide As 2 O 3 (“white arsenic”).

The name arsenikon is found already at the beginning of our era; it is derived from the Greek arsen - strong, courageous and served to designate arsenic compounds (based on their effect on the body). The Russian name is believed to come from “mysh” (“death” - after the use of arsenic preparations to kill yaks, as well as exterminate mice and rats). The chemical production of free arsenic is attributed to 1250 AD. In 1789, A. Lavoisier included arsenic in the list of chemical elements.

Arsenic. Belorechenskoye deposit, North. Caucasus, Russia. ~10x7 cm. Photo: A.A. Evseev.

Distribution of arsenic in nature.

The average arsenic content in the earth's crust (clarke) is 1.7 * 10 -4% (by mass), in such quantities it is present in most igneous rocks. Since arsenic compounds are volatile at high temperatures (dry volcanic sublimation on batholiths), the element sublimes into the atmosphere and air in the form of metal vapors (mirages - the air below ripples) does not accumulate during magmatic lava processes sublimating through cracks and tubes; it is concentrated, deposited from vapors and hot deep waters on crystal formation catalysts - metallic iron (together with S, Se, Sb, Fe, Co, Ni, Cu and other elements).

During volcanic eruptions (during dry sublimation of arsenic), arsenic in the form of its volatile compounds enters the atmosphere. Since arsenic is multivalent, its migration is influenced by the redox environment. Under oxidizing conditions of the earth's surface, arsenates (As 5+) and arsenites (As 3+) are formed.

These are rare minerals found in areas of arsenic deposits. Native arsenic and As 2+ minerals are even less common. Of the minerals and arsenic compounds (about 180), arsenopyrite FeAsS is of industrial importance (the iron atom is the center of pyrite formation, the formula of the starting “single crystal” is Fe + (As + S)).

Arsenopyrite vein. Trifonovskaya mine, Kochkarskoe deposit (Au), Plast, South Ural, Russia. Arsenics. Photo: A.A. Evseev.

Small amounts of arsenic are essential for life. However, in areas of arsenic deposits and the activity of young volcanoes, soils in some places contain up to 1% arsenic, which is associated with livestock diseases and death of vegetation. The accumulation of arsenic is especially typical for landscapes of steppes and deserts, in the soils of which arsenic is inactive. In humid climates and when plants and soils are watered, arsenic is washed out of the soil.

In living matter there is an average of 3·10 -5% arsenic, in rivers 3·10 -7%. Arsenic carried by rivers into the ocean precipitates relatively quickly. In sea water there is 1 * 10 -7% arsenic (there is a lot of gold there, which displaces it), but in clays and shales there is arsenic (along the banks of rivers and reservoirs, in clayey black formations and along the edges of quarries) - 6.6 * 10 - 4 %. Sedimentary iron ores, ferromanganese and other iron nodules are often enriched in arsenic.

Physical properties of arsenic.

Arsenic has several allotropic modifications. Under normal conditions, the most stable is the so-called metallic, or gray, arsenic (α-As) - steel gray fragile crystalline mass (according to properties - like pyrite, gold blende, iron pyrite); when freshly fractured, it has a metallic luster; in air it quickly becomes dull, as it is covered with a thin film of As 2 O 3 .

Arsenic is rarely called silver blende - the case of the Tsar's Clerks A.M. Romanov in the middle of the 17th century, “silver”, not malleable, comes in powder, can be ground - poison for the Tsar of All Rus'. The most famous Spanish scandal in the poisoners' tavern near the Don Quixote mill on the road to Almaden, Spain, where red cinnabar is mined on the European continent (scandals about the sale of virgins in the Krasnodar Territory of the Russian Federation, the village of Novy, crystalline red cinnabar, do not want to work) .

Arsenopyrite. Druze of prismatic crystals with calcite spherulites. Freiberg, Saxony, Germany. Photo: A.A. Evseev.

The crystal lattice of gray arsenic is rhombohedral (a = 4.123Å, angle α = 54 o 10", x = 0.226), layered. Density 5.72 g/cm 3 (at 20 o C), electrical resistivity 35 * 10 -8 ohm *m, or 35*10 -6 ohm*cm, temperature coefficient of electrical resistance 3.9·10 -3 (0 o -100 o C), Brinell hardness 1470 MN/m 2, or 147 kgf/mm 2 (3- 4 according to Moocy); arsenic is diamagnetic.

Under atmospheric pressure, arsenic sublimes at 615 o C without melting, since the triple point of α-As lies at 816 o C and a pressure of 36 at.

Arsenic vapor consists of As 4 molecules up to 800 o C, above 1700 o C - only As 2. When arsenic vapor condenses on a surface cooled by liquid air, yellow arsenic is formed - transparent, wax-soft crystals with a density of 1.97 g/cm 3, similar in properties to white phosphorus.

When exposed to light or low heat, it turns into gray arsenic. Glassy-amorphous modifications are known: black arsenic and brown arsenic, which, when heated above 270 o C, turn into gray arsenic

Chemical properties of arsenic.

The configuration of the outer electrons of the arsenic atom is 3d 10 4s 2 4p 3. In compounds, arsenic has oxidation states +5, +3 and -3. Gray arsenic is less chemically active than phosphorus. When heated in air above 400 o C, arsenic burns, forming As 2 O 3.

Arsenic combines directly with halogens; under normal conditions, AsF 5 is a gas; AsF 3 , AsCl 3 , AsBr 3 - colorless volatile liquids; AsI 3 and As 2 I 4 are red crystals. When arsenic is heated with sulfur, sulfides are obtained: orange-red As 4 S 4 and lemon-yellow As 2 S 3.

Pale yellow silver sulfide As 2 S 5 ( arsenopyrite) is deposited by passing H 2 S into an ice-cooled solution of arsenic acid (or its salts) in fuming hydrochloric acid: 2H 3 AsO 4 + 5H 2 S = As 2 S 5 + 8H 2 O; At about 500 o C it decomposes into As 2 S 3 and sulfur.

All arsenic sulfides are insoluble in water and dilute acids. Strong oxidizing agents (mixtures of HNO 3 + HCl, HCl + KClO 3) convert them into a mixture of H 3 AsO 4 and H 2 SO 4.

As 2 S 3 sulfide easily dissolves in sulfides and polysulfides of ammonium and alkali metals, forming salts of acids - thioarsenic H 3 AsS 3 and thioarsenic H 3 AsS 4 .

With oxygen, arsenic produces oxides: arsenic oxide (III) As 2 O 3 - arsenous anhydride and arsenic oxide (V) As 2 O 5 - arsenic anhydride. The first of them is formed by the action of oxygen on arsenic or its sulfides, for example 2As 2 S 3 + 9O 2 = 2As 2 O 3 + 6SO 2.

As 2 O 3 vapors condense into a colorless glassy mass, which becomes opaque over time due to the formation of small cubic crystals, density 3.865 g/cm 3 . The vapor density corresponds to the formula As 4 O 6; above 1800 o C the steam consists of As 2 O 3.

2.1 g of As 2 O 3 dissolves in 100 g of water (at 25 o C). Arsenic (III) oxide is an amphoteric compound with a predominance of acidic properties. Salts (arsenites) corresponding to orthoarsenic acids H 3 AsO 3 and metaarsenic HAsO 2 are known; the acids themselves have not been obtained. Only alkali metal and ammonium arsenites are soluble in water.

As 2 O 3 and arsenites are usually reducing agents (for example, As 2 O 3 + 2I 2 + 5H 2 O = 4HI + 2H 3 AsO 4), but can also be oxidizing agents (for example, As 2 O 3 + 3C = 2As + 3SO ).

Arsenic (V) oxide is prepared by heating arsenic acid H 3 AsO 4 (about 200 o C). It is colorless, at about 500 o C it decomposes into As 2 O 3 and O 2. Arsenic acid is obtained by the action of concentrated HNO 3 on As or As 2 O 3.

Arsenic acid salts (arsenates) are insoluble in water, with the exception of alkali metal and ammonium salts. Salts are known that correspond to the acids orthoarsenic H 3 AsO 4 , metaarsenic HAsO 3 and pyroarsenic H 4 As 2 O 7 ; the last two acids were not obtained in a free state. When alloyed with metals, arsenic mostly forms compounds (arsenides).

Obtaining arsenic.

Arsenic is produced industrially by heating arsenic pyrites:

FeAsS = FeS + As

or (less often) reduction of As 2 O 3 with coal. Both processes are carried out in retorts made of refractory clay connected to a receiver for condensing arsenic vapor.

Arsenic anhydride is obtained by oxidative roasting of arsenic ores or as a by-product of roasting polymetallic ores, which almost always contain arsenic. During oxidative roasting, As 2 O 3 vapors are formed, which condense in the collection chambers.

Crude As 2 O 3 is purified by sublimation at 500-600 o C. Purified As 2 O 3 is used for the production of arsenic and its preparations.

Use of arsenic.

Small additions of arsenic (0.2-1.0% by weight) are introduced into lead used for the production of gun shot (arsenic increases the surface tension of molten lead, due to which the shot takes on a shape close to spherical; arsenic slightly increases the hardness of lead). As a partial substitute for antimony, arsenic is included in some babbitt and printing alloys.

Pure arsenic is not poisonous, but all its compounds that are soluble in water or can go into solution under the influence of gastric juice are extremely poisonous; Arsenic hydrogen is especially dangerous. Of the arsenic compounds used in production, arsenic anhydride is the most toxic.

Almost all sulfide ores of non-ferrous metals, as well as iron (sulfur) pyrite, contain an admixture of arsenic. Therefore, during their oxidative roasting, along with sulfur dioxide SO 2, As 2 O 3 is always formed; Most of it condenses in the smoke channels, but in the absence or low efficiency of treatment facilities, the exhaust gases of ore kilns carry away noticeable amounts of As 2 O 3.

Pure arsenic, although not poisonous, is always covered with a coating of toxic As 2 O 3 when stored in air. In the absence of properly performed ventilation, etching of metals (iron, zinc) with industrial sulfuric or hydrochloric acids containing arsenic is extremely dangerous, since this produces arsenic hydrogen.

Arsenic in the body.

As a trace element, arsenic is ubiquitous in living nature. The average arsenic content in soils is 4*10 -4%, in plant ash - 3*10 -5%. The arsenic content in marine organisms is higher than in terrestrial organisms (in fish 0.6-4.7 mg per 1 kg of raw material, accumulates in the liver).

The largest amount of it (per 1 g of tissue) is found in the kidneys and liver (when ingested, it does not accumulate in the brain). A lot of arsenic is found in the lungs and spleen, skin and hair; relatively little - in the cerebrospinal fluid, brain (mainly in the pituitary gland), gonads and others.

In tissues, arsenic is found mainly protein fraction(“the stone of bodybuilders and athletes”), much less - in the acid-soluble and only a small part of it is found in the lipid fraction. It is used to treat progressive muscular dystrophy - it does not accumulate in the brain and bones (sports doping, treated for hostages and prisoners of concentration camps such as "Auschwitz" in Poland, EU, 1941-1944).

Arsenic is involved in redox reactions: oxidative breakdown of complex biological carbohydrates and sugars, fermentation, glycolysis, etc. Improves mental abilities (promotes the process of breaking down sugars in the brain). Arsenic compounds are used in biochemistry as specific enzyme inhibitors to study metabolic reactions. Promotes the breakdown of biological tissues (accelerates). It is actively used in dentistry and oncology - to eliminate rapidly growing and early aging cancer cells and tumors.

Mixture (hard sulfide alloy) of thallium, arsenic and lead: Hutchinsonite (Hutchinsonite)

The mineral formula is (Pb, Tl)S` Ag2S * 5 As2 S5 - complex sulfide and adsenide carbide salt. Rhombus. The crystals are prismatic to needle-shaped. Cleavage perfect according to (010). The aggregates are radial-needle-shaped, granular. Hardness 1.5-2. Specific gravity 4.6. Red. Diamond shine. In hydrothermal deposits with dolomite, with sulfides and arsenides of Zn, Fe, As and sulfoarsenides. The result of dry sulfuric and arsenic sublimation of magma through calderas and open volcanic vents, as well as dry sublimation through cracks in deep igneous plutonites from the hot magma of the Earth. Contains silver. It is one of the ten very dangerous to human and animal health and carcinogenic stones and minerals that crystallize in modern conditions among other rocks in the form of harmful, hazardous to health (if handled without permission) and deceptive ore beauty. In the photo - Hutchinsonite with orpiment.

Poisonous minerals. Hutchinsonite - named after the mineralogist Hutchinson from the University of Cambridge and resembles lead in appearance (it can be used for protection against radiation). Opened in 1861. A deadly mixture (hard alloy) of thallium, arsenic and lead. Contact with this mineral can lead to hair loss (alopecia, baldness, baldness), complex skin diseases and death. All of its main components are poisonous. Very similar to lead, native silver, pyrite ("dry pyrite") and arsenopyrite. It is also similar to stibnite (an antimony compound, also very poisonous). Also similar to zeolites. Hutchinsonite is a dangerous and striking carbide mixture of thallium, lead and arsenic. Three rare, very expensive and valuable ore metals form a toxic, lethal cocktail of minerals that must be handled with the utmost care. Affects the brain, heart and liver simultaneously.

Thallium is lead's dark counterpart. This dense, fatty metal is similar in atomic mass to lead, but is even more deadly. Thallium is a rare metal that appears in highly toxic compounds consisting of strange combinations of elements (hard alloys). The effects of thallium exposure are more dangerous than lead, and include hair loss (alopecia, baldness), serious illness from skin contact, and in many cases death. Hutchinsonite was named after John Hutchinson, a famous mineralogist at the University of Cambridge. This mineral can be found in mountainous regions of Europe, most often in ore deposits. A mineral popular in medical dentistry, etc. Alcoholics are afraid of the mineral.

Hutchinsonite (Hutchinsonite) is sometimes jokingly called “dry” or “solid alcohol”, “solid alcohol” (and not only for the harmful effects of intoxicating poisoning on the body and human health). The chemical formula of food alcohol (alcohol) is C2 H5 (OH). Hutchinsonite (Hutchinsonite) has a chemical formula - 5 As2 S5 * (Pb, Tl) S` Ag2 S or 5 As2 S5 * (Pb, Tl) S` Ag Ag S. The formula of Hutchinsonite (Hutchinsonite) is sometimes rewritten differently - As2 S5 * ( Pb) + As2 S5 * (Tl) + As2 S5 * S + As2 S5 * Ag + As2 S5 * AgS. Chemical separation of components in production is also carried out according to the type of different alcohols (layers of mechanical enrichment, different in mass and weight, which are crushed by ultrasound and separated in a centrifuge or on a vibration platform - the horror movie "Aliens"). Other similar variations of the chemical formula are possible (composition varies).

ADR 6.1
Toxic substances (poison)
Risk of poisoning through inhalation, skin contact or ingestion. Hazardous to the aquatic environment or sewerage system
Use a mask when leaving a vehicle in an emergency

ADR 3
Flammable liquids
Fire risk. Risk of explosion. Containers can explode when heated (extremely dangerous - burn easily)

ADR 2.1
Flammable gases
Fire risk. Risk of explosion. May be under pressure. Risk of suffocation. May cause burns and/or frostbite. Containers can explode when heated (extremely dangerous - practically do not burn)
Use cover. Avoid low surface areas (holes, lowlands, trenches)
Red diamond, ADR number, black or white flame

ADR 2.2
Gas cylinder Non-flammable, non-toxic gases.
Risk of suffocation. May be under pressure. They can cause frostbite (similar to a burn - pallor, blisters, black gas gangrene - creaking). Containers can explode when heated (extremely dangerous - explosion from a spark, flame, match, practically do not burn)
Use cover. Avoid low surface areas (holes, lowlands, trenches)
Green diamond, ADR number, black or white gas cylinder (cylinder, thermos type)

ADR 2.3
Toxic gases. Skull and crossbones
Danger of poisoning. May be under pressure. May cause burns and/or frostbite. Containers can explode when heated (extremely dangerous - instantaneous spread of gases throughout the surrounding area)
Use a mask when leaving a vehicle in an emergency. Use cover. Avoid low surface areas (holes, lowlands, trenches)
White diamond, ADR number, black skull and crossbones

Arsenic(Latin arsenicum), as, chemical element of group V of the periodic system of Mendeleev, atomic number 33, atomic mass 74.9216; steel-gray crystals. The element consists of one stable isotope 75 as.

Historical reference. Natural compounds of minerals with sulfur (orpiment as 2 s 3, realgar as 4 s 4) were known to the peoples of the ancient world, who used these minerals as medicines and paints. The product of burning M. sulfides was also known - M. oxide (iii) as 2 o 3 (“white M.”). The name arsenik o n is already found in Aristotle; it is derived from the Greek. a rsen - strong, courageous and served to designate M compounds (according to their strong effect on the body). The Russian name is believed to come from “mouse” (from the use of M. preparations for the extermination of mice and rats). The receipt of M. in a free state is attributed to Albert the Great(about 1250). In 1789 A. Lavoisier included M. in the list of chemical elements.

Distribution in nature. The average content of metal in the earth's crust (clarke) is 1.7 × 10 -4% (by mass); it is present in such quantities in most igneous rocks. Since M. compounds are volatile at high temperatures, the element does not accumulate during magmatic processes; it concentrates, precipitating from hot deep waters (together with s, se, sb, fe, co, ni, cu and other elements). During volcanic eruptions, minerals enter the atmosphere in the form of their volatile compounds. Since M. is multivalent, its migration is greatly influenced by the redox environment. Under oxidizing conditions of the earth's surface, arsenates (as 5+) and arsenites (as 3+) are formed. These are rare minerals, found only in areas of mineral deposits. Native mineral and as 2+ minerals are even less common. Of the numerous minerals of M. (about 180), only arsenopyrite feass is of primary industrial importance.

Small amounts of M. are necessary for life. However, in areas with mineral deposits and the activity of young volcanoes, the soils in some places contain up to 1% metal, which is associated with livestock diseases and the death of vegetation. The accumulation of M. is especially characteristic of landscapes of steppes and deserts, in the soils of which M. is inactive. In humid climates, M. is easily washed out of the soil.

In living matter there is an average of 3 × 10 -5% M, in rivers 3 × 10 -7%. M., brought by rivers to the ocean, settles out relatively quickly. In sea water there is only 1 x 10 -7% M, but in clays and shales it is 6.6 x 10 -4%. Sedimentary iron ores and ferromanganese nodules are often enriched in M.

Physical and chemical properties. M. has several allotropic modifications. Under normal conditions, the most stable is the so-called metallic, or gray, M. (a -as) - a steel-gray brittle crystalline mass; when freshly fractured, it has a metallic luster; in air it quickly fades because it is covered with a thin film of as 2 o 3. The crystal lattice of gray M. is rhombohedral ( A= 4.123 a, angle a = 54°10", X= 0.226), layered. Density 5.72 g/cm 3(at 20°c), electrical resistivity 35 10 -8 ohm? m, or 35 10 -6 ohm? cm, temperature coefficient of electrical resistance 3.9 10 -3 (0°-100 °c), Brinell hardness 1470 Mn/m 2, or 147 kgf/mm 2(3-4 according to Mohs); M. diamagnetic. Under atmospheric pressure, metal sublimes at 615 °C without melting, since the triple point a -as lies at 816 °C and a pressure of 36 at. M. steam consists of as 4 molecules up to 800 ° C, above 1700 ° C - only of as 2. When vapor of metal condenses on a surface cooled by liquid air, yellow metal is formed - transparent crystals, soft like wax, with a density of 1.97 g/cm 3, similar in properties to white phosphorus. When exposed to light or weak heating, it turns into gray M. Glassy-amorphous modifications are also known: black M. and brown M., which turn into gray M when heated above 270°c.

Configuration of the outer electrons of the atom M. 3 d 10 4 s 2 4 p 3. In compounds, M has oxidation states of + 5, + 3, and – 3. Gray M is significantly less chemically active than phosphorus. When heated in air above 400°c, M burns, forming as 2 o 3. M combines directly with halogens; under normal conditions asf 5 - gas; asf 3, ascl 3, asbr 3 - colorless, highly volatile liquids; asi 3 and as 2 l 4 - red crystals. When M. is heated with sulfur, the following sulfides are obtained: orange-red as 4 s 4 and lemon-yellow as 2 s 3. Pale yellow sulfide as 2 s 5 is precipitated by passing h 2 s into an ice-cooled solution of arsenic acid (or its salts) in fuming hydrochloric acid: 2h 3 aso 4 + 5h 2 s = as 2 s 5 + 8h 2 o; At about 500°c it decomposes into as 2 s 3 and sulfur. All M. sulfides are insoluble in water and dilute acids. Strong oxidizing agents (mixtures hno 3 + hcl, hcl + kclo 3) convert them into a mixture of h 3 aso 4 and h 2 so 4. Sulfide as 2 s 3 easily dissolves in sulfides and polysulfides of ammonium and alkali metals, forming salts of acids - thioarsenic h 3 ass 3 and thioarsenic h 3 ass 4. With oxygen, M. produces oxides: M. oxide (iii) as 2 o 3 - arsenic anhydride and M. oxide (v) as 2 o 5 - arsenic anhydride. The first of them is formed by the action of oxygen on metal or its sulfides, for example 2as 2 s 3 + 9o 2 = 2as 2 o 3 + 6so 2. As 2 o 3 vapors condense into a colorless glassy mass, which becomes opaque over time due to the formation of small cubic crystals, density 3.865 g/cm 3. The vapor density corresponds to the formula as 4 o 6: above 1800°c steam consists of as 2 o 3. At 100 G water dissolves 2.1 G as 2 o 3 (at 25°c). M. oxide (iii) is an amphoteric compound, with a predominance of acidic properties. Salts (arsenites) corresponding to orthoarsenic acids h 3 aso 3 and metaarsenic haso 2 are known; the acids themselves have not been obtained. Only alkali metal and ammonium arsenites are soluble in water. as 2 o 3 and arsenites are usually reducing agents (for example, as 2 o 3 + 2i 2 + 5h 2 o = 4hi + 2h 3 aso 4), but can also be oxidizing agents (for example, as 2 o 3 + 3c = 2as + 3co ).

M. oxide (v) is obtained by heating arsenic acid h 3 aso 4 (about 200°c). It is colorless, at about 500°c it decomposes into as 2 o 3 and o 2. Arsenic acid is obtained by the action of concentrated hno 3 on as or as 2 o 3. Arsenic acid salts (arsenates) are insoluble in water, with the exception of alkali metal and ammonium salts. Salts are known that correspond to the acids orthoarsenic h 3 aso 4 , metaarsenic haso 3 , and pyroarsenic acid h 4 as 2 o 7 ; the last two acids were not obtained in a free state. When fused with metals, metal mostly forms compounds ( arsenides).

Receipt and use . M. is produced industrially by heating arsenic pyrites:

feass = fes + as

or (less often) reduction of as 2 o 3 with coal. Both processes are carried out in retorts made of refractory clay, connected to a receiver for condensation of M vapors. Arsenic anhydride is obtained by oxidative roasting of arsenic ores or as a by-product of roasting polymetallic ores, which almost always contain M. During oxidative roasting, as 2 o 3 vapors are formed, which condense into catch chambers. Crude as 2 o 3 is purified by sublimation at 500-600°c. Purified as 2 o 3 is used for the production of M. and its preparations.

Small additives of M (0.2-1.0% by weight) are introduced into lead used for the production of gun shot (M increases the surface tension of molten lead, due to which the shot acquires a shape close to spherical; M slightly increases the hardness of lead ). As a partial substitute for antimony, M. is included in some babbitts and printing alloys.

Pure M. is not poisonous, but all its compounds that are soluble in water or can go into solution under the influence of gastric juice are extremely poisonous; especially dangerous arsenous hydrogen. Of the M compounds used in production, arsenous anhydride is the most toxic. Almost all sulfide ores of non-ferrous metals, as well as iron (sulfur) pyrite, contain metal admixtures. Therefore, during their oxidative roasting, along with sulfur dioxide so 2, as 2 o 3 is always formed; Most of it condenses in the smoke channels, but in the absence or low efficiency of treatment facilities, the exhaust gases of ore kilns carry away noticeable amounts of as 2 o 3. Pure M., although not poisonous, is always covered with a coating of poisonous as 2 o 3 when stored in air. In the absence of proper ventilation, etching of metals (iron, zinc) with industrial sulfuric or hydrochloric acids containing an admixture of metals is extremely dangerous, since this produces arsenous hydrogen.

S. A. Pogodin.

M. in the body. As trace element M. is ubiquitous in living nature. The average content of M in soils is 4 · 10 -4%, in plant ashes - 3 · 10 -5%. The M content in marine organisms is higher than in terrestrial organisms (in fish 0.6-4.7 mg in 1 kg crude matter accumulates in the liver). The average content of M in the human body is 0.08-0.2 mg/kg. In the blood, M. is concentrated in erythrocytes, where it binds to the hemoglobin molecule (and the globin fraction contains twice as much as heme). The largest amount of it (per 1 G tissue) is found in the kidneys and liver. A lot of M. is found in the lungs and spleen, skin and hair; relatively little - in the cerebrospinal fluid, brain (mainly the pituitary gland), gonads, etc. In tissues, M. is found in the main protein fraction, much less in the acid-soluble fraction, and only a small part of it is found in the lipid fraction. M. participates in redox reactions: oxidative breakdown of complex carbohydrates, fermentation, glycolysis, etc. M. compounds are used in biochemistry as specific inhibitors enzymes for studying metabolic reactions.

M. in medicine. Organic compounds of M. (aminarsone, miarsenol, novarsenal, osarsol) are used mainly for the treatment of syphilis and protozoal diseases. Inorganic preparations of M. - sodium arsenite (sodium arsenate), potassium arsenite (potassium arsenate), arsenic anhydride as 2 o 3, are prescribed as general strengthening and tonic agents. When applied topically, inorganic M. preparations can cause a necrotizing effect without previous irritation, making this process almost painless; This property, which is most pronounced in as 2 o 3, is used in dentistry to destroy dental pulp. Inorganic M. preparations are also used to treat psoriasis.

Artificially obtained radioactive isotopes M. 74 as (t 1 / 2 = 17.5 days) and 76 as (t 1 / 2 = 26.8 h) are used for diagnostic and therapeutic purposes. With their help, the location of brain tumors is clarified and the degree of radicality of their removal is determined. Radioactive M. is sometimes used for blood diseases, etc.

According to the recommendations of the International Commission on Radiation Protection, the maximum permissible content of 76 as in the body is 11 mccurie. According to sanitary standards adopted in the USSR, the maximum permissible concentrations of 76 as in water and open reservoirs are 1 10 -7 curie/l, in the air of working premises 5 10 -11 curie/l. All M. preparations are very poisonous. In case of acute poisoning, severe abdominal pain, diarrhea, and kidney damage are observed; Collapse and convulsions are possible. In chronic poisoning, the most common are gastrointestinal disorders, catarrh of the mucous membranes of the respiratory tract (pharyngitis, laryngitis, bronchitis), skin lesions (exanthema, melanosis, hyperkeratosis), and sensitivity disorders; the development of aplastic anemia is possible. In the treatment of poisoning with M. drugs, unithiol is of greatest importance.

Measures to prevent industrial poisonings should be aimed primarily at mechanization, sealing and dust removal of the technological process, creating effective ventilation and providing workers with personal protective equipment from exposure to dust. Regular medical examinations of workers are necessary. Preliminary medical examinations are carried out upon hiring, and for employees - once every six months.

Lit.: Remi G., Course of inorganic chemistry, trans. from German, vol. 1, M., 1963, p. 700-712; Pogodin S. A., Arsenic, in the book: Brief chemical encyclopedia, vol. 3, M., 1964; Harmful substances in industry, under general. ed. N. V. Lazareva, 6th ed., part 2, Leningrad, 1971.

download abstract

People have known elemental arsenic and the toxic properties of its compounds for a very long time. This conclusion can be reached knowing that the method for determining death from arsenic poisoning, which is still used today, was created by James Marshais in 1836.

Arsenic, or the “king of poisons,” is a simple substance that is rarely found in nature in a free form. It is a metal with a fragile structure, gray in color with a slightly greenish tint and a pronounced steely sheen.

In its crystalline state it is similar to other metals and has good thermal and electrical conductivity, but its non-metallic properties are much more pronounced. For example, any arsenic hydroxide is an acid.

Elemental arsenic, as well as any of its compounds, is extremely poisonous, but it is quite difficult to obtain such substances, since it reacts with the vast majority of metals and non-metals only at very high temperatures.

For thousands of years, the elemental arsenic metal and its oxides were mistaken for the same substance. Clarity was brought only at the end of the 18th century. In the chemical periodic table, the name of arsenic (33As) sounds like arsenic, from the Latin arsenicum - a direct borrowing from the Greek language, which in turn is a transformation of zarnik. This is exactly what the ancient Persians and Assyrians called the well-known yellow orpiment (arsenic sulfide).

The origin of the Russian name is attributed to the folk phrase “mouse” and “poison”, since the oxide for a long time was the only effective substance for controlling rodents.

Production and applications

To date, just over 200 minerals are known to contain arsenic. In most cases, it is present in deposits of silver, copper or lead ore. However, the mineral that is of primary industrial importance is arsenic pyrite or arsenopyrite.

Among the numerous ways to obtain metallic (gray) arsenic is the roasting of arsenopyrite with the subsequent reduction of its oxide using anthracite coal, but the main part of the raw material is processed into white arsenic or arsenic trioxide - arsenic anhydride.

The use of gray arsenic, a silvery, coarse-crystalline metal, is especially important for metallurgical production because it is used:

• as a flux or alloying additive for the production of certain alloys;
• as an additive that increases the hardness of lead and copper products and increases the surface tension of liquid lead.

The use of arsenic III - arsenic trioxide, is much wider:

• in agriculture - seed treatment, control of plant diseases, destruction of insect pests and rodents;
• in the glass industry - production of glass with easy fusibility, colorless glass, as well as in the production of mirrors;
• in the leather industry – leather preservation;
• in laboratory chemical analyzes arsenic salts are analytical reagents;
• protection against rotting of wooden products for external use - sleepers, poles, fences;
• insoluble arsenic salts are used for the manufacture of materials for semiconductors, including ion-selective membranes;
• production of chemical warfare agents – persistent lewisite and poisonous-smoky adamsite;
• in medicine – for the manufacture of medicines, and also in dental treatment – ​​as an anesthetic.

Industrial safety

The following basic safety measures for working with arsenic are currently approved:

• complete tightness of the equipment;
• using intensive ventilation to remove gases, powder and dust, as well as performing air analysis according to the established schedule;
• use of personal protective equipment: goggles, gloves, special suits, and, if necessary, a gas mask;

Each branch of production has its own special rules, and safety training of workers is carried out against signature annually, once a quarter. Women and boys under 18 years of age are not allowed to work with arsenic, and men are required to undergo quarterly medical examinations.

Possible causes of poisoning

Is it possible to get poisoned by arsenic today? Of course yes, because none of the workers is insured against accidents at work, and when using arsenic-based poisons in everyday life, it may accidentally enter the body. Sometimes intentional cases of poisoning are recorded - suicide or murder. All of these episodes are classified as acute poisoning.

Arsenic poisoning can also occur through occupational exposure to small doses, as well as through prolonged consumption of contaminated water or taking medications. Such poisonings are classified as chronic.

A special, subacute category of poisoning includes cases of a person coming into contact with adamsite, which is used by police in some countries to disperse mass demonstrations. In poisons classified as chemical warfare agents, adamsite occupies a position among sternites - compounds that irritate the upper respiratory tract.

Another common cause of arsenic poisoning is the collection of mushrooms in places where chemical weapons are destroyed or unscrupulous disposal of waste containing arsenic. In the fruiting bodies of mushrooms growing in such areas, the concentration of arsenic exceeds the permissible limit by 1,000 times, but they taste and smell no different from the same mushrooms growing in neighboring “clean” areas. Moreover, scientists have come to the conclusion that mycelia prefer soils rich in arsenic, so eating mushrooms purchased second-hand without appropriate laboratory analysis is quite reckless.

We should not forget that acute, subacute or chronic arsenic poisoning can also be caused by improper washing of vegetables or fruits, since arsenic-based preparations are actively used to control rodents in storage facilities.

The effect of arsenic on the human body

Arsenic quickly and easily penetrates the skin, lungs and gastrointestinal tract, while inorganic compounds, arsenic trioxide, are absorbed more easily than organic ones. The most dangerous gas for humans is arsine gas or arsenous hydrogen. In its pure form, arsine does not smell of anything, so before using it in production, a special admixture is added to it, after which it acquires the smell of garlic.

After penetrating inside, within 24 hours arsenic affects all internal organs, entering them through the bloodstream, and after 2 weeks its traces can be found in bones, skin, hair and nails.

It takes a long time for arsenic to be eliminated from the body, because only about 7% is excreted in feces. And despite the fact that urine excretes 93%, even after taking a single dose, and after 10 days, traces of it are still present in it.

Regardless of the route of penetration, arsenic acts as follows:

• Once in the blood plasma, it forms a strong bond with hemoglobin;
• through blood vessels it reaches all organs, including tissues of the nervous system;
• causes a disruption in the biochemistry of cellular respiration.

Symptoms

The characteristic symptoms of arsenic poisoning depend on the dose of the substance received.

The lethal dose for a person due to arsenic poisoning, if arsenic trioxide was ingested, is between 50 and 340 mg. Its value directly depends on the state of health and weight of the person, as well as what type of toxic substance was used.

For arsenic hydrogen, the lethal indicators are as follows:

• inhalation of gas for 15 minutes with a concentration of 0.6 mg/l;
• 5 min – 1.3 mg/l;
• several breaths – 2-4 mg/l;
• instantly – 5 mg/l.

Signs of poisoning depend on the type of lesion:

• Acute form– there is a metallic taste in the mouth, accompanied by a burning sensation in the throat and laryngeal spasms. The skin becomes bluish, and the sclera of the eyes and palms turn yellow. Blood pressure drops and severe attacks of dizziness occur. Acute renal and liver failure develops. The stomach hurts severely and uncontrollable diarrhea occurs, which quickly removes fluid from the body, resulting in dehydration. In severe cases, possible: spasm or pulmonary edema, paralysis, loss of consciousness and coma.
• Subacute form– severe irritation of the eyes and mucous membranes, leading to watery eyes and a “runny nose.” Sneezing, coughing and chest tightness. Nausea and vomiting are possible, with a metallic aftertaste in the mouth. I have a particularly severe headache.
• Chronic form– anemic conditions, general malaise and rapid physical fatigue. Weakness of the limbs, loss of peripheral sensitivity, numbness of skin areas and “pins and needles” occur. Sustained rosacea, telangiectasia and spider veins develop throughout the body. Dangerous consequences are possible - the development of encephalopathy and toxic hepatitis. Due to its high carcinogenicity, arsenic can be an impetus for the development of cancer.

A typical sign of chronic arsenic poisoning is white stripes on the nails.

In men who work for a long time in hazardous work, arsenic poisoning causes symptoms and the following changes:

• hyperkeratosis - excessive growth of the surface layers of the skin;
• dryness, peeling and peeling of the skin on all parts of the body;
• increased red pigmentation in the temples, eyelids, neck, armpits, nipples and scrotum;
• Transverse white stripes appear on the nails.

Arsenic poisoning in dentistry

Arsenic is used in medicine as a component of some drugs that cause local and general effects. It can help cause irritation, cauterize or anesthetize, and act as a regulator of metabolism and hematopoiesis. Preparations based on organic arsenic compounds are widely used for chemotherapy, spirochetosis, and other numerous diseases caused by protozoa, as well as for the treatment of syphilis, relapsing fever, malaria, and Simanovsky-Vincent angina.

Since arsenic pastes are still used in domestic dentistry, many people are tormented by questions: why are they used and is arsenic poisoning possible during dental treatment, how long can you keep arsenic in a tooth, and what will happen if you swallow arsenic from a tooth? Let's answer briefly and in order:

• after arsenic, the nerve in the tooth dies;
• gray arsenic pastes are used in private dental offices as an anesthetic for devitalizing the pulp if it is impossible to use modern means due to their intolerance, and in public offices this is possible either the old fashioned way or because of their cheapness;
• Even a child cannot be poisoned by arsenic paste during dental treatment;
• You can keep devitalizing pastes on single-rooted teeth for a maximum of 24 hours, and on others only up to 48 hours, otherwise the tooth will turn black;
• Depulpin paste can be kept for 2 weeks;
• If you eat cotton wool with arsenic paste, nothing bad will happen, but it’s still better to follow the following procedures:
  • thoroughly rinse the oral cavity and tooth cavity with a lukewarm infusion of chamomile or a weakly concentrated soda solution;
  • place a dry cotton ball into the tooth cavity;
  • optional, but to “calm the soul”, if you have it, take any kind of sorbent or drink a glass of milk, you can eat 100 g of cottage cheese;
  • visit a doctor soon.

On a note. You should not endure toothache under a filling with arsenic paste. An unscheduled visit to the dentist is necessary.

First aid for poisoning

How to behave in case of arsenic poisoning and how to remove it from the body? When providing first aid, you should adhere to the following algorithm:

1. Call an ambulance and provide fresh air into the room.
2. Give an emetic.
3. Rinse the stomach generously.
4. Give milk with whipped protein or give any available sorbent.
5. Place a hot heating pad on your stomach.
6. If you eat, drink several glasses of the solution - 1 tablespoon of burnt magnesia dissolved in 200 ml of water.
7. It is forbidden to drink sour drinks and inhale ammonia.
8. If there are cramps, actively rub your limbs.

Is there an antidote for arsenic and where can I get one?

In medical centers of enterprises where arsenic is used, the first aid kit of the joint venture must contain a specific antidote - unitol.

In cases of careless household poisoning, you should report your suspicions to the emergency medical operator so that the team can administer it immediately upon arrival.

Treatment

Therapeutic actions depend on the severity of intoxication. For acute poisoning, injections of dimercaprol (unitol) are used:

• on the first day, every 6 hours, 2-3 mg/kg;
• 2-5 days after poisoning - every 12 hours;
• 6-10 days – 1 time per day.

For severe symptoms, the dose of unitol is increased to 3-5 mg/kg.

To relieve abdominal pain, injections of atropine with morphine are used, and to prevent the outflow of fluid from the body, droppers of saline solution with glucose and adrenaline, intravenous administration of calcium chloride and sodium thiosulfate are used. For abdominal pain, injections of morphine with atropine are given. In case of acute renal failure, hemodialysis and/or exchange blood transfusion are used.

When treating chronic forms of poisoning, D-penicillamine is used in courses of 5 days.

Arsenic- a mineral from the class of native elements, a semimetal, chemical formula As. Common impurities are Sb, S, Fe, Ag, Ni; less commonly Bi and V. The As content in native arsenic reaches 98%. Chemical element of the 15th group (according to the outdated classification - the main subgroup of the fifth group) of the fourth period of the periodic table; has atomic number 33. Arsenic (crude arsenic) is a solid extracted from natural arsenopyrites. It exists in two main forms: ordinary, so-called “metallic” arsenic, in the form of shiny steel-colored crystals, brittle, insoluble in water, and yellow arsenic, crystalline, rather unstable. Arsenic is used in the production of arsenic disulfide, shot, hard bronze and various other alloys (tin, copper, etc.)

See also:

STRUCTURE

Several allotropic modifications of arsenic have been identified. Under normal conditions, metallic or gray arsenic (alpha arsenic) is stable. The crystal lattice of gray arsenic is rhombohedral, layered, with a period a = 4.123 A, angle a = 54° 10′. Density (at a temperature of 20° C) 5.72 g/cm 3 ; temperature coefficient linear expansion 3.36 10 degrees; specific electrical resistance (temperature 0° C) 35 10 -6 ohm cm; NV = f 147; coefficient compressibility (at a temperature of 30° C) 4.5 x 10 -6 cm 2 /kg. The melting point of alpha-arsenic is 816 ° C at a pressure of 36 atmospheres.

Under atm. Arsenic sublimes under pressure at a temperature of 615° C without melting. Heat of sublimation 102 cal/g. Arsenic vapor is colorless, up to a temperature of 800° C they consist of As 4 molecules, from 800 to 1700° C - from a mixture of As 4 and As 2, above a temperature of 1700° C - only from As 2. With the rapid condensation of arsenic vapor on a surface cooled by liquid air, yellow arsenic is formed - transparent soft crystals of a cubic system with a density of 1.97 g/cm 3 . Other metastable modifications of arsenic are also known: beta-arsenic - amorphous glassy, ​​gamma-arsenic - yellow-brown and delta-arsenic - brown amorphous with densities of 4.73, respectively; 4.97 and 5.10 g/cm3. Above a temperature of 270° C, these modifications turn into gray arsenic.

PROPERTIES

The color on a fresh fracture is zinc-white, tin-white to light gray, quickly fades due to the formation of dark gray tarnish; black on a weathered surface. Hardness on the Mohs scale 3 - 3.5. Density 5.63 - 5.8 g/cm3. Fragile. Diagnosed by the characteristic smell of garlic when struck. Cleavage is perfect according to (0001) and less perfect according to (0112). The fracture is grainy. Ud. weight 5.63-5.78. The line is gray, pewter-white. The luster is metallic, strong (when freshly fractured), quickly fades and becomes dull on an oxidized surface that has become blackened over time. Is diamagnetic.

MORPHOLOGY

ORIGIN

Arsenic occurs in hydrothermal deposits as metacolloidal formations in voids, apparently formed during the last moments of hydrothermal activity. In association with it, arsenic, antimonous, and, less commonly, sulfur compounds of nickel, cobalt, silver, lead, etc., of various compositions, as well as non-metallic minerals, can be found.

In the literature there are indications of the secondary origin of arsenic in weathering zones of arsenic ore deposits, which, generally speaking, is unlikely, given that under these conditions it is very unstable and, quickly oxidizing, decomposes completely. The black crusts consist of a fine mixture of arsenic and arsenolite (As 2 O 3). Eventually pure arsenolite is formed.

In the earth's crust, the concentration of arsenic is low and amounts to 1.5 ppm. It is found in soil and minerals and can be released into the air, water and soil through wind and water erosion. In addition, the element enters the atmosphere from other sources. As a result of volcanic eruptions, about 3 thousand tons of arsenic are released into the air per year, microorganisms produce 20 thousand tons of volatile methylarsine per year, and as a result of the combustion of fossil fuels, 80 thousand tons are released over the same period.

On the territory of the USSR, native arsenic was found in several deposits. Of these, we note the Sadon hydrothermal lead-zinc deposit, where it was repeatedly observed in the form of kidney-shaped masses on crystalline calcite with galena and sphalerite. Large kidney-shaped accumulations of native arsenic with a concentric shell-like structure were found on the left bank of the river. Chikoya (Transbaikalia). In paragenesis with it, only calcite was observed in the form of rims on the walls of thin veins cutting across ancient crystalline schists. In the form of fragments (Fig. 76), arsenic was also found in the area of ​​st. Jalinda, Amurskaya railway etc. and in other places.

In a number of deposits in Saxony (Freiberg, Schneeberg, Annaberg, etc.), native arsenic was observed in association with arsenic compounds of cobalt, nickel, silver, native bismuth, etc. All these and other finds of this mineral are of no practical significance.

APPLICATION

Arsenic sulfide compounds - orpiment and realgar - are used in painting as paints and in the leather industry as means for removing hair from the skin. In pyrotechnics, realgar is used to produce “Greek” or “Indian” fire, which occurs when a mixture of realgar with sulfur and nitrate burns (when burned, it forms a bright white flame).
Some organoelement compounds of arsenic are chemical warfare agents, for example, lewisite.

At the beginning of the 20th century, some cacodyl derivatives, for example, salvarsan, were used to treat syphilis; over time, these drugs were displaced from medical use for the treatment of syphilis by other, less toxic and more effective, pharmaceutical drugs that do not contain arsenic.

Many of the arsenic compounds in very small doses are used as drugs to combat anemia and a number of other serious diseases, as they have a clinically noticeable stimulating effect on a number of specific functions of the body, in particular, on hematopoiesis. Of the inorganic arsenic compounds, arsenous anhydride can be used in medicine for the preparation of pills and in dental practice in the form of a paste as a necrotizing drug. This drug was colloquially and colloquially called “arsenic” and was used in dentistry for local necrosis of the dental nerve. Currently, arsenic preparations are rarely used in dental practice due to their toxicity. Now other methods of painless necrosis of the tooth nerve under local anesthesia have been developed and are being used.

Arsenic - As

CLASSIFICATION

Arsenic is a non-metal and forms compounds similar in its chemical properties. However, along with non-metallic properties, arsenic also exhibits metallic ones. In air under normal conditions, arsenic is slightly oxidized from the surface. Arsenic and its analogues are insoluble neither in water nor in organic solvents.

Arsenic is chemically active. In air at normal temperatures, even compact (fused) metallic arsenic is easily oxidized; when heated, powdered arsenic ignites and burns with a blue flame to form As 2 O 3 oxide. Thermally less stable non-volatile oxide As 2 O 5 is also known.

When heated (in the absence of air), As sublimes (sublimation temperature 615 o C). The steam consists of As 4 molecules with an insignificant (about 0.03%) admixture of As 2 molecules.

Arsenic belongs to the group of oxidizing-reducing elements. When exposed to strong reducing agents, it exhibits oxidizing properties. Thus, under the action of metals and hydrogen at the moment of release, it is capable of producing the corresponding metal and hydrogen compounds:

6Ca +As 4 = 2Ca 3 As 2

Under the influence of strong oxidizing agents, arsenic transforms into a tri- or pentavalent state. For example, when heated in air, arsenic, oxidized by oxygen, burns and forms white smoke - arsenic (III) oxide As 2 O 3:

As 4 + 3O 2 =2As 2 O 3

Stable forms of arsenic oxide in the gas phase are sesquioxide (arsenic anhydride) As 2 O 3 and its dimer As 4 O 6. Up to 300 o C, the main form in the gas phase is a dimer; above this temperature it is noticeably dissociated, and at temperatures above 1800 o C the gaseous oxide consists practically of monomeric As 2 O 3 molecules.

A gaseous mixture of As 4 O 6 and As 2 O 3 is formed during the combustion of As in oxygen, during the oxidative roasting of As sulfide minerals, such as arsenopyrite, non-ferrous metal ores and polymer ores.

When As 2 O 3 (As 4 O 6) vapor condenses above 310 o C, the glassy form of As 2 O 3 is formed. When steam condenses below 310 o C, a colorless polycrystalline cubic modification of arsenolite is formed. All forms of As 2 O 3 are highly soluble in acids and alkalis.

As(V) oxide (arsenic anhydride) As 2 O 5 – colorless crystals of the orthorhombic system. When heated, As 2 O 5 dissociates into As 4 O 6 (gas) and O 2 . As 2 O 5 is obtained by dehydrating concentrated solutions of H 3 AsO 4 followed by calcination of the resulting hydrates.

The oxide As 2 O 4 is known, obtained by sintering As 2 O 3 and As 2 O 5 at 280 o C in the presence of water vapor. Gaseous AsO monoxide is also known, which is formed during an electrical discharge in As trioxide vapor at reduced pressure.

When dissolved in water, As 2 O 5 forms orthoarsenic H 3 AsO 3 , or As(OH) 3 , and metaarsenic HAsO 2 , or AsO(OH), which exist only in solution and have amphoteric, predominantly acidic, properties.

In relation to acids, arsenic behaves as follows:

— arsenic does not react with hydrochloric acid, but in the presence of oxygen arsenic trichloride AsCl 3 is formed:

4As +3O 2 +12HCl = 4AsCl 3 +6H 2 O

- dilute nitric acid, when heated, oxidizes arsenic to orthoarsenic acid H 3 AsO 3 , and concentrated nitric acid – to orthoarsenic acid H 3 AsO 4:

3As + 5HNO 3 + 2H 2 O = 3H 2 AsO 4 +5NO

Orthoarsenic acid(arsenic acid) H 3 AsO 4 *0.5H 2 O – colorless crystals; melting point – 36 o C (with decomposition); soluble in water (88% by weight at 20 o C); hygroscopic; in aqueous solutions – tribasic acid; when heated to about 100 o C, it loses water, turning into pyroarsenic acid H 4 As 5 O 7, at higher temperatures it turns into metaarsenic acid HAsO 3. Obtained by oxidation of As or As 2 O 3 with concentrated HNO 3 . It is easily soluble in water and is approximately equal in strength to phosphorus.

The oxidizing properties of arsenic acid are noticeable only in an acidic environment. Arsenic acid is capable of oxidizing HI to I 2 by reversible reactions:

H 3 AsO 4 + 2HI = H 3 AsO 3 + I 2 + H 2 O

Orthoarsenic acid (arsenous acid) H 3 AsO 3 exists only in aqueous solution; weak acid; obtained by dissolving As 2 O 3 in water; intermediate product in the preparation of arsenites (III) and other compounds.

- concentrated sulfuric acid reacts with arsenic according to the following equation to form orthoarsenic acids:

2As + 3H 2 SO 4 = 2H 3 AsO 3 +3SO 2

- alkali solutions do not react with arsenic in the absence of oxygen. When arsenic is boiled with alkalis, it is oxidized into the arsenic acid salt H 3 AsO 3 . When fused with alkalis, arsine (arsenous hydrogen) AsH 3 and arsenates (III) are formed. Apply AsH 3

for doping semiconductor materials with arsenic to obtain high purity As.

Unstable higher arsines are known: diarsine As 2 H 4, decomposes already at -100 o C; triarsine As 3 H 5 .

Metallic arsenic easily reacts with halogens, giving volatile halides AsHal 3:

As +3Cl 2 = 2AsCl 3

AsCl 3 is a colorless oily liquid that fumes in air and, when solidified, forms crystals with a pearlescent sheen.

C F 2 also forms AsF 5 - pentafluoride - a colorless gas, soluble in water and alkali solutions (with a small amount of heat), in diethyl ether, ethanol and benzene.

Powdered arsenic spontaneously ignites in an environment of F 2 and Cl 2 .

With S, Se and Te, arsenic forms the corresponding chalcogenides:

sulfides - As 2 S 5, As 2 S 3 (orpiment mineral in nature), As 4 S 4 (realgar mineral) and As 4 S 3 (dimorphite mineral); selenides – As 2 Se 3 and As 4 Se 4; telluride – As 2 Te 3 . Arsenic chalcogenides are stable in air, insoluble in water, highly soluble in alkali solutions, and when heated - in HNO 3. They have semiconductor properties and are transparent in the IR region of the spectrum.

With most metals it gives metallic compounds - arsenides. Gallium arsenide and indium arsenide– important semiconductor compounds.

There are numerous known arsenicorganic connections. Organoarsenic compounds contain an As-C bond. Sometimes organoarsenic compounds include all organic compounds containing As, for example, esters of arsenic acid (RO) 3 As and arsenic acid (RO) 3 AsO. The most numerous group of organoarsenic compounds are As derivatives with a coordination number of 3. This includes organoarsines R n AsH 3-n, tetraorganodiarsines R 2 As-AsR 2, cyclic and linear polyarganoarsines (RAs) n, as well as organoarsonic and diarganoarsinous acids and their derivatives R n AsX 3-n (X= OH, SH, Hal, OR', NR 2', etc.). Most organoarsenic compounds are liquids, polyorganoarsines and organic acids As are solids, CH 3 AsH 2 and CF 3 AsH 2 are gases. These compounds, as a rule, are soluble in organic solvents, limitedly soluble in water, and relatively stable in the absence of oxygen and moisture. Some tetraorganodiarsines are flammable in air.