Arsenic structure. Hazardous element arsenic - areas of application

As known to mankind since ancient times. Already the great Aristotle mentioned the chemical element arsenic in natural compounds. In addition, the possibility of developing its sulphurous variety, by calcination, is described by Dioscorides in the first century BC.

Later, European steelworkers encountered this element when working with ore, interspersed with arsenic. The alchemists studied it very closely. Such attention was explained by the fact that he, like sulfur and mercury, belonged to the elemental elements, which are the basis of all metals.

The ability of arsenic to change the color of copper alloys to white was perceived by professors of modern chemistry as a metamorphosis of copper into silver. Now in the world, not a single laboratory can do without this element.

As is present everywhere. Even a smoked cigarette has its content, which, among other things, determines the harmfulness of smoking.

The discovery of arsenic on a metal base dates back to the eighteenth century, however, the method of obtaining the element using sublimation will only be revealed by the end of the seventeenth. During this period, the chemist Scheele discovered arsenic acid, as well as the hydrogen present in it.

The study of organic compounds containing As originates from the chemist Kade. In the middle of the eighteenth century, he obtains the first compound of an organic nature based on it - "Cade Liquid". The structure was disassembled into its components only after eighty years by another famous chemist Bunsen.

Until now, there are disputes about who to give the palm to the discovery of the element in its purest form. This achievement is credited to the merits of Albert the Great. It was recognized as a chemical element by Lavoisier in 1789.

Production and applications

Modern experts know about two hundred minerals that contain arsenic. In the vast majority of cases, it is found in ore containing copper, silver or lead. However, the mineral of major importance for industry is pyrites with arsenic.

There are several ways to produce As on an industrial scale. The main type of production was the firing of arsenopyrite. Further, oxide is reduced from it by means of anthracite.

However, most of the raw materials with this method are converted into white arsenic.

Arsenic in the dental field

This chemical element is not only a poison, but also a medicine.

The use of arsenic in the field of dentistry in the form of a paste has not lost its significance due to the bright necrotic effect of the substance on the affected tissues.

It is applied in the following cases:

• If the patient does not perceive anesthetics;
• In cases of contraindications of anesthetic drugs;
• In the treatment of toothache in children.

The main condition for its use in dental clinics is a fully formed root system. Therefore, the "children's" version of the application is not so common.

As in industry

The chemical element arsenic is used in many areas of production, among which there are several main areas:

• Metallurgy;
• Electrical engineering;
• Leather processing;
• Textile industry;
• Pyrotechnics;
• Glass production.

Metallurgy- used for alloying lead alloys used for the manufacture of shot. Such an alloy with the addition of As in the turret version of production makes it possible to obtain ideal spherical shapes of pellets. In addition, its strength increases.

electrical engineering– highly purified arsenic (up to 99%) is used to manufacture a number of necessary semiconductor components.

Textile industry- used as a dye.

leather industry- in this area it is used as a reagent for the destruction of bristles on the skin.

Pyrotechnics- the mineral realgar, which is arsenic monosulfide, is used to make "Greek" fire, which is obtained by igniting a mixture of it with sulfur and nitrate. This chemical compound produces a bright white flame.

glass business- As trioxide makes it possible to obtain products with zero transparency. Meanwhile, small additions of the component, on the contrary, lighten it. This element is still part of the production of some glasses.

For example:

• "Vienna";
• used in thermometers;
• Crystal imitations.

In addition, arsenic is also used in agriculture as a fertilizer. Home use is rat poison. Now it is made on the basis of other components.

Eating is strictly prohibited.

Arsenic in the fight against leukemia

Known to poisoners, the ability of arsenic to kill cells is now used for noble purposes. This chemical element is widely used to treat cancer, primarily leukemia.

Leukemia is characterized by tumor formation due to bone marrow replication. In the absence of timely treatment, there is an increase in its volume. For this reason, metastases arise and grow in all parts of the body. The As element helps to cure even a severe form of the disease.

It effectively neutralizes the excessive growth of leukocytes, stimulates the rapid and high-quality formation of red cells. All this allows you to positively influence the recovery process. When treating this dangerous element, clear instructions must be followed. After all, the ultimate price is human life.

Possible causes of poisoning

Nowadays, there is a high risk of poisoning with arsenic. None of the workers in production is immune from various surprises. When using As-based substances in domestic conditions, there is also a possibility of accidental ingestion into the human body.

Sometimes facts of deliberate poisoning are recorded - criminal offenses or suicide. These episodes can be attributed to acute forms of intoxication.

There is a possibility of poisoning in the medical practice of exposure to small doses. Such poisoning is classified as chronic cases.

A separate group of intoxication with this chemical element is the subacute category. When a person is present in places where there is a large concentration of adamsite.

It is used by police officers in some countries to disperse demonstrations. Combat is divided into several categories, including sternites. Arsenic is one of them. Such substances are irritating to the human respiratory apparatus.

The effect of arsenic on the body

The element has the ability to quickly penetrate into the human body, and it is very difficult to remove it.

Poisoning occurs in the following ways:

• Integuments;
• Lungs;
• Gastrointestinal tract.

It should be noted that the inorganic components of arsenic are absorbed much faster than organics.

The greatest danger to humans is arsine in a gaseous state, it does not smell, so for its industrial production it is necessary to make special additives that have a persistent garlic "aroma". Arsenic hydrogen is also dangerous.

Poisoning occurs very quickly. During the day, the element is able to hit the internal organs. Two weeks after intoxication, traces of arsenic can be found in the nails and even in the bones.

Symptoms of arsenic poisoning

Symptoms of the disease may vary depending on the dose taken.

• acute form

Characterized by a metallic persistent taste in the mouth. A person feels a strong throat burning sensation, accompanied by spasms. The skin on the body acquires a bluish tint, and the palms turn yellow.

Blood pressure drops sharply, accompanied by powerful bouts of dizziness. In addition, the poisoned person experiences acute renal and hepatic failure.

Also, the patient has diarrhea and the stomach begins to hurt badly. Diarrhea is characterized by an acute form, as a result of which the body is very quickly dehydrated. In extreme cases, there is a high chance of pulmonary edema, paralysis, or a comatose state.

• Subacute form

There is an extremely severe headache. All mucous membranes are strongly irritated, especially the eyes and respiratory tract. This leads to a runny nose, nasal congestion and watery eyes.

The victim often sneezes and coughs. Severe nausea and even vomiting are also not ruled out. After spasms, an aftertaste with a metallic tint remains in the mouth.

• Chronic form

Fatigue and general malaise set in. Limbs weaken against the background of an anemic condition. Peripheral sensitivity worsens up to a complete loss. Goosebumps run along the skin and its numbness is felt.

Asterisks from the vessels appear on the body and stable rosacea develops.

In the absence of appropriate treatment, serious consequences are very likely up to. Since arsenic is highly carcinogenic, poisoning can lead to the development of oncology in the body.

For a person who has swallowed arsenic trioxide, the lethal dose will be from 50 to 340 milligrams. It is tied to the type of substance and is directly related to a person's weight and overall health.

First aid for poisoning

If you or someone close to you or colleagues accidentally poisoned yourself with arsenic, you should provide immediate assistance before the arrival of specialists.

Actions are carried out according to a simple algorithm:

• The first thing to do is to immediately call an ambulance;
• Before the arrival of doctors, give the victim an emetic to wash the stomach;
• The next step is to take an absorbent (for example, milk with whipped protein or activated charcoal);
• Put a hot heating pad on the victim's stomach;
• If possible, prepare a special solution consisting of one spoonful of burnt magnesia per 200 ml of water;
• In no case should the victim be allowed to smell ammonia or sour drink;
• If convulsions occur, rub the limbs of the victim.

As is a strong poison that can cause great harm.

Unitol became the main antidote for arsenic. This is an effective antidote that has the ability to bind it into safe compounds and allows you to get rid of the chemical element with urea.

Timely preventive measures also help to remove the toxicological effect of arsenic when working in production.

How to prevent poisoning

As a prevention of poisoning, try to avoid foods containing it. Sealing of production processes and improvement of ventilation are carried out at workplaces.

Personal hygiene plays a huge role in the prevention of poisoning. Respirators must be used in the workplace. Or use cotton swabs that are placed in the ears and nostrils. After work, be sure to wash. In addition, keep an eye on your overalls. Keep it clean and washed.

A mandatory preventive measure should be a regular medical examination. Such examinations are recommended to take place at least twelve months with constant contact with preparations containing arsenic.

Some who died in the Middle Ages from cholera did not die from it. The symptoms of the disease are similar to those arsenic poisoning.

Having learned this, medieval businessmen began to offer element trioxide as a poison. Substance. The lethal dose is only 60 grams.

They were divided into portions, giving for several weeks. In the end, no one suspected that the man did not die from cholera.

Arsenic taste is not felt in small doses, being, for example, in food or drinks. In modern realities, of course, there is no cholera.

People do not have to be afraid of arsenic. More likely, mice need to be afraid. A toxic substance is a type of poison for rodents.

In their honor, by the way, the element is named. The word "arsenic" exists only in Russian-speaking countries. The official name of the substance is arsenicum.

Designation in - As. The serial number is 33. Based on it, we can assume a complete list of the properties of arsenic. But let's not assume. Let's look into the matter for sure.

Properties of arsenic

The Latin name of the element is translated as "strong". Apparently, this refers to the effect of the substance on the body.

With intoxication, vomiting begins, digestion is upset, the stomach twists and the work of the nervous system is partially blocked. not one of the weak.

Poisoning occurs from any of the allotropic forms of the substance. Alltropy is the existence of manifestations of the same thing that are different in structure and properties. element. Arsenic most stable in metallic form.

Rhombohedral steel gray brittle. The units have a characteristic metallic, but from contact with moist air, they dim.

Arsenic - metal, whose density is almost 6 grams per cubic centimeter. For other forms of the element, the indicator is less.

In second place is amorphous arsenic. Element characteristic: — almost black color.

The density of this form is 4.7 grams per cubic centimeter. Outwardly, the material resembles.

The usual state of arsenic for the inhabitants is yellow. Cubic crystallization is unstable, it becomes amorphous when heated to 280 degrees Celsius, or under the action of simple light.

Therefore, yellows are soft, like in the dark. Despite the color, the aggregates are transparent.

From a number of modifications of the element, it can be seen that it is only half the metal. The obvious answer to the question is:- " Arsenic metal or non-metal", No.

Chemical reactions serve as confirmation. The 33rd element is acid-forming. However, being in acid itself does not give.

Metals do things differently. In the case of arsenic, they are not obtained even upon contact with, one of the strongest.

Salt-like compounds are "born" during the reactions of arsenic with active metals.

I mean oxidizers. The 33rd substance interacts only with them. If the partner does not have pronounced oxidizing properties, the interaction will not take place.

This applies even to alkalis. I.e, arsenic is a chemical element pretty inert. How, then, to get it, if the list of reactions is very limited?

Arsenic mining

Arsenic is mined along with other metals. Separate them, the 33rd substance remains.

In nature there are compounds of arsenic with other elements. It is from them that the 33rd metal is extracted.

The process is profitable, since, together with arsenic, they often go,, and.

It is found in granular masses, or cubic crystals of tin color. Sometimes, there is a yellow tint.

Arsenic compound and metal ferrum has a "brother", in which instead of the 33rd substance is . It is an ordinary golden-colored pyrite.

The aggregates are similar to arsenoversion, but they cannot serve as arsenic ore, although they also contain it as an impurity.

Arsenic in the usual, by the way, also happens, but, again, as an impurity.

The amount of element per ton is so small, but even secondary extraction does not make sense.

If you evenly distribute the world's reserves of arsenic in the earth's crust, you get only 5 grams per ton.

So, the element is not common, it is comparable in number to , , .

If you look at the metals with which arsenic forms minerals, then this is not only, but also with cobalt and nickel.

The total number of minerals of the 33rd element reaches 200. There is also a native form of matter.

Its presence is explained by the chemical inertness of arsenic. Formed next to elements with which reactions are not provided, the hero remains in splendid isolation.

In this case, often, needle-shaped, or cubic aggregates are obtained. Usually, they grow together.

Application of arsenic

The element arsenic belongs to dual, not only showing the properties of both metal and non-metal.

The perception of the element by humanity is also dual. In Europe, the 33rd substance has always been considered a poison.

In 1733, they even issued a decree prohibiting the sale and purchase of arsenic.

In Asia, the "poison" has been used by physicians for 2000 years in the treatment of psoriasis and syphilis.

Modern doctors have proven that the 33rd element attacks proteins that provoke oncology.

In the 20th century, some European doctors also sided with the Asians. In 1906, for example, Western pharmacists invented the drug salvarsan.

He became the first in official medicine, was used against a number of infectious diseases.

True, immunity is developed to the drug, as well as to any constant intake of arsenic in small doses.

Effective 1-2 courses of the drug. If immunity is formed, people can take a lethal dose of the element and stay alive.

In addition to physicians, metallurgists became interested in the 33rd element, starting to add in for the production of shots.

It is done on the basis of which is included in heavy metals. Arsenic increases the lead and allows its splashes to take on a spherical shape when cast. It is correct, which improves the quality of the shot.

Arsenic can also be found in thermometers, or rather them. It is called Viennese, mixed with the oxide of the 33rd substance.

The connection serves as a clarifier. Arsenic was also used by glassblowers of antiquity, but as a matting additive.

Opaque glass becomes with an impressive impurity of a toxic element.

Keeping proportions, many glassblowers fell ill and died prematurely.

And tanneries use sulfides arsenic.

Element main subgroups The 5th group of the periodic table is part of some paints. In the leather industry, arsenicum helps to remove hair from.

Arsenic price

Pure arsenic is most often offered in metallic form. Prices are set per kilogram, or ton.

1000 grams costs about 70 rubles. For metallurgists, they offer ready-made, for example, arsenic with copper.

In this case, they take 1500-1900 rubles per kilo. Kilograms sell and arsenic anhydrite.

It is used as a skin medicine. The agent is necrotic, that is, it dies the affected area, killing not only the causative agent of the disease, but also the cells themselves. The method is radical, but effective.

Arsenic (= Arsene) (As)

The main weapon of poisoners or a sexual stimulant?

Arsenic belong to conditionally essential, immunotoxic for the human body elements.

Arsenic has been known since ancient times both as medicine and as poison. The poisons of Locusta were famous in Rome; in Venice, for example, poisoners were kept at the court. And the main component of almost all poisons was arsenic. There is an assumption that Napoleon was poisoned with arsenic on Saint Helena .

Symptoms of arsenic poisoning- metallic taste in the mouth, vomiting, severe abdominal pain, later - convulsions, paralysis, death.

It is currently established that in small doses, arsenic is necessary for the human body: it prevents the loss of phosphorus . Just as vitamin D regulates phosphorus-calcium metabolism, so arsenic regulates phosphorus metabolism.
But if the concentration of arsenic in food or in the soil oversteps the limit and approaches poisonous doses, then the number of deaths caused by cancer of the larynx, eyes or leukemia will increase.

The daily requirement of the human body- 12–15 mcg. A deficiency of this element in the body can develop with its insufficient intake (1 mcg / day or less).

In total, the human body contains about 15 mg of arsenic.

Arsenic compounds enter the human body with drinking and mineral water, grape wines and juices, seafood, medicines, pesticides and herbicides.

About 80% of arsenic is absorbed in the gastrointestinal tract, 10% comes through the lungs and about 1% through the skin.

More than 90% of inorganic arsenic compounds are soluble and well absorbed. Further, inorganic arsenic moves to the liver, where it is methylated. Arsenic accumulates in the lungs, liver, skin, and small intestine. Arsenic is deposited mainly in the reticuloendothelial system, probably as a result of the association of arsenite with SH-groups of proteins, which are relatively more in these tissues.
24 hours after intake, 30% of arsenic is excreted from the body with urine and about 4% with feces. Insignificant quantities are removed with sweat, with fallen hair, exfoliated skin and bile.

Biological role in the human body. It is known that arsenic interacts with thiol groups of proteins, cysteine, glutathione, and lipoic acid. Perhaps arsenic is involved in some enzymatic reactions. As an enzyme activator, arsenic probably acts as a substitute for phosphate. As an inhibitor, arsenic apparently reacts with the sulfhydryl groups of enzymes.

Arsenic affects oxidative processes in mitochondria, participates in nucleic metabolism, i.e. is directly related to protein synthesis, and is necessary for the synthesis of hemoglobin, although it is not included in its composition.

It is known that arsenic is present in the organism of mammals in the reduced forms of As, NaAs 3+ , which are considered as potential stimulators of the formation of metallothionein with CdCl 2 .

It was believed that "microdoses of arsenic, introduced with care into a growing organism, contribute to the growth of human and animal bones in length and thickness, in some cases, bone growth can be caused by microdoses of arsenic even after the end of general growth." However, these data have not found scientific confirmation.

Currently the effect of microdoses of preparations containing arsenic as anticancer agents is being studied .

Synergists and antagonists of arsenic. Arsenic can accumulate heavily in the body with selenium deficiency, and thus contribute to selenium deficiency.
Arsenic antagonists are sulfur, phosphorus, selenium, vitamins C, E and amino acids.
Arsenic inhibits the body's absorption of zinc, selenium, ascorbic acid, vitamins A and E, and amino acids.

Signs of arsenic deficiency: in humans - dermatitis, anemia; in animals, a decrease in growth and abnormal reproduction, characterized by high perinatal mortality.
Other known symptoms: low serum triglycerides.

target organs with an excess of arsenic in the body is the bone marrow, gastrointestinal tract, skin, lungs and kidneys. Arsenic and all its compounds are poisonous to varying degrees. .

Arsenic belongs to the so-called "thiol poisons" . The mechanism of its toxicity is associated with a violation of the metabolism of sulfur, selenium and phosphorus. The toxicity of arsenic depends on the chemical properties and decreases in the following order: arsine AsH3 > inorganic As 3+ > organic As 3+ > inorganic As 5+ > arsonium compounds AsH 4+ > elemental arsenic.

There is enough evidence carcinogenicity of inorganic arsenic compounds. A high mortality rate from lung cancer has been reported among workers employed in the production of pesticides, gold mining and the smelting of arsenic alloys with other metals, as well as non-ferrous metals and especially copper. As a result of prolonged use of arsenic-contaminated water or drugs, the development of poorly differentiated skin cancer (Bowen's cancer) is often observed. Probably, liver hemangioendothelioma is also an arsene-dependent tumor.

A small excess of arsenic in the diet causes abnormal fertility in animals., which is characterized by significant increased sexual activity and fertility.

A man-made environmental disaster in southern India received wide publicity - due to increased water withdrawal from aquifers, arsenic began to enter drinking water. This caused toxic and oncological damage in tens of thousands of people.

Reasons for excess arsenic: excessive intake (constant contact with arsenic, environmental pollution, smoking, abuse of grape wine, long-term administration of salvarsan preparations), dysregulation of arsenic metabolism; increased accumulation of arsenic in the body with selenium deficiency.

The main manifestations of excess arsenic: irritability, headaches, impaired liver function, development of fatty hepatosis; skin allergic reactions, eczema, dermatitis, itching, ulcers, skin depigmentation, palmoplantar hyperkeratosis; conjunctivitis; damage to the respiratory system (fibrosis, allergies, nasal septal rupture, tumors); vascular lesions (primarily of the lower extremities - endoangiitis) nephropathy, an increased risk of developing skin, liver, and lung neoplasms.

For acute arsenic poisoning observed abdominal pain, vomiting, diarrhea, depression of the central nervous system; develop: intravascular hemolysis, acute renal, hepatic failure, cardiogenic shock. The similarity of the symptoms of arsenic poisoning with the symptoms of cholera for a long time made it possible to successfully use arsenic compounds (most often arsenic trioxide) as a deadly poison.

In areas where there is an excess of arsenic in soil and water, it accumulates in the thyroid gland of humans and causes endemic goiter.

Arsenic in small doses is carcinogenic. However, for a long time (until the mid-1950s) it was used as a "blood-improving" drug. Such use in most cases led to the development of oncological diseases.

Long-term effects of arsenic intoxication: decreased hearing acuity in children, damage to the nervous system (encephalopathy, speech disorders, coordination of movements, convulsions, psychoses, polyneuritis with pain syndrome), impaired muscle trophism, immunodeficiency.

Arsenic is needed: with inflammatory processes caused by protozoal and microbial damage, with some forms of allergies, with anemia, to increase appetite.
When poisoning a person or domestic animals (dogs, birds, pigs, cows) with large doses of selenium, arsenic is an antidote. In experiments conducted on mice, it was possible to reduce the incidence of cancer with the help of specially selected doses of arsenic. Arsenic in water is less than 10 µg/l, however, in some regions of the world (India, Bangladesh, Taiwan, Mexico) the content of this element reaches more than 1 mg/l, which is the cause of massive chronic arsenic poisoning and causes the so-called "black foot" disease .

Arsenic(lat. arsenicum), as, a chemical element of the v group 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.

History reference. M.'s natural compounds 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 sulfides of M. was also known - the oxide of M. (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 have come from "mouse" (according to the use of M.'s preparations for the extermination of mice and rats). Getting M. in a free state is attributed Albert the Great(about 1250). In 1789 A. Lavoisier included M. in the list of chemical elements.

distribution in nature. The average content of M. in the earth's crust (clarke) is 1.7 × 10 -4% (by mass), in such quantities it is present in most igneous rocks. Since M.'s compounds are volatile at high temperatures, the element does not accumulate during magmatic processes; it is concentrated by precipitating from hot deep waters (together with s, se, sb, fe, co, ni, cu, and other elements). During volcanic eruptions, M. in the form of its volatile compounds enters the atmosphere. Since M. is multivalent, its migration is greatly influenced by the redox environment. Under the 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 rarer. Of the numerous minerals of M. (about 180), only arsenopyrite feass is of major industrial importance.

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

In living matter, on average, 3 × 10 -5% M., in rivers 3 × 10 -7%. M., brought by rivers into the ocean, is relatively quickly precipitated. In sea water, only 1 10 -7% M., but in clays and shales 6.6 10 -4%. Sedimentary iron ores, 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 gray-steel brittle crystalline mass; in a fresh fracture it has a metallic luster, quickly tarnishes in air, 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. is diamagnetic. Under atmospheric pressure, M. sublimates at 615 ° C without melting, since the triple point a -as lies at 816 ° C and a pressure of 36 at. Steam M. up to 800 ° C consists of molecules as 4, above 1700 ° C - only from as 2. During the condensation of vapor M. on a surface cooled by liquid air, yellow M. is formed - transparent, wax-soft crystals, with a density of 1.97 g/cm 3, similar in properties to white phosphorus. Under the action of light or upon slight heating, it turns into gray M. Glassy-amorphous modifications are also known: black M. and brown M., which, when heated above 270 ° C, turn into gray M.

The configuration of the outer electrons of the atom M. 3 d 10 4 s 2 4 p 3 . In compounds, M. has the oxidation states + 5, + 3, and - 3. Gray M. is much less chemically active than phosphorus. When heated in air above 400 ° C, M. burns, forming as 2 o 3. M. connects to halogens directly; under normal conditions asf 5 - gas; asf 3 , ascl 3 , asbr 3 - colorless, easily volatile liquids; asi 3 and as 2 l 4 are red crystals. When M. is heated with sulfur, sulfides are obtained: orange-red as 4 s 4 and lemon-yellow as 2 s 3 . Pale yellow sulfide as 2 s 5 precipitates when h 2 s is passed into an ice-cooled solution of arsenic acid (or its salts) in fuming hydrochloric acid: 2h 3 aso 4 + 5h 2 s \u003d as 2 s 5 + 8h 2 o; around 500°c it decomposes into as 2 s 3 and sulfur. All M.'s 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. Sulfide as 2 s 3 is easily soluble in sulfides and polysulfides of ammonium and alkali metals, forming salts of acids - thioarsenous h 3 ass 3 and thioarsenic h 3 ass 4 . With oxygen, M. gives oxides: oxide M. (iii) as 2 o 3 - arsenic anhydride and oxide M. (v) as 2 o 5 - arsenic anhydride. The first of these is formed by the action of oxygen on M. or its sulfides, for example, 2as 2 s 3 + 9o 2 \u003d 2as 2 o 3 + 6so 2. Vapors as 2 o 3 condense into a colorless vitreous mass, which becomes opaque over time due to the formation of small crystals of cubic system, density 3.865 g/cm 3. The vapor density corresponds to the formula as 4 o 6: above 1800°c, the vapor consists of as 2 o 3 . At 100 G water dissolves 2.1 G as 2 o 3 (at 25°c). Oxide M. (iii) is an amphoteric compound, with a predominance of acidic properties. Salts (arsenites) are known that correspond to orthoarsenic h 3 aso 3 and metaarsenic haso 2 acids; 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 \u003d 4hi + 2h 3 aso 4), but they can also be oxidizing agents (for example, as 2 o 3 + 3c \u003d 2as + 3co ).

Oxide M. (v) is obtained by heating arsenic acid h 3 aso 4 (about 200°c). It is colorless, about 500°c 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 . Salts of arsenic acid (arsenates) are insoluble in water, with the exception of alkali metal and ammonium salts. Salts corresponding to acids orthoarsenic h 3 aso 4 , metaarsenic haso 3 , and pyroarsenic h 4 as 2 o 7 are known; the last two acids have not been obtained in the free state. When fused with metals, M. for the most part forms compounds ( arsenides).

Getting and using . M. is obtained in industry by heating arsenic pyrites:

feass = fes + as

or (more rarely) as 2 o 3 reduction with charcoal. Both processes are carried out in refractory clay retorts connected to a receiver for condensing M vapor. 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 capture 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 shotgun 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 part of some babbits and printing alloys.

Pure M. is not poisonous, but all its compounds that are soluble in water or that can go into solution under the action of gastric juice are extremely poisonous; especially dangerous arsenic hydrogen. Of the compounds used in the production of M., arsenic anhydride is the most toxic. Almost all sulfide ores of non-ferrous metals, as well as iron (sulfur) pyrite, contain an admixture of M.. 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 entrain significant 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, it is extremely dangerous to etch metals (iron, zinc) with technical sulfuric or hydrochloric acids containing an admixture of M., since arsenic hydrogen is formed in this case.

S. A. Pogodin.

M. in the body. As trace element M. is ubiquitous in wildlife. The average content of M. in soils is 4 10 -4%, in plant ash - 3 10 -5%. The content of M. in marine organisms is higher than in terrestrial ones (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 (moreover, the globin fraction contains twice as much of it as the heme). The largest amount of it (per 1 G tissue) is found in the kidneys and liver. A lot of M. is contained in the lungs and spleen, skin and hair; relatively little - in the cerebrospinal fluid, brain (mainly the pituitary gland), gonads, etc. In the tissues of M. is in the main protein fraction, much less - in the acid-soluble and only a small part of it is found in the lipid fraction. M. is involved in redox reactions: oxidative breakdown of complex carbohydrates, fermentation, glycolysis, etc. M. compounds are used in biochemistry as specific inhibitors enzymes to study metabolic reactions.

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

Artificially obtained radioactive isotopes M. 74 as (t 1 / 2 = 17.5 day) and 76 as (t 1/2 = 26.8 h) are used for diagnostic and therapeutic purposes. With their help, the localization of brain tumors is clarified and the degree of radicalness 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 allowable content of 76 as in the body is 11 microcurie. According to the 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 rooms 5 10 -11 curie/l. All M.'s preparations are very poisonous. In acute poisoning, they experience severe abdominal pain, diarrhea, kidney damage; possible collapse, convulsions. In chronic poisoning, the most common are gastrointestinal disorders, catarrhs ​​of the mucous membranes of the respiratory tract (pharyngitis, laryngitis, bronchitis), skin lesions (exanthema, melanosis, hyperkeratosis), sensitivity disorders; possible development of aplastic anemia. In the treatment of poisoning with M.'s drugs, unithiol is of the greatest importance.

Measures to prevent industrial poisoning should be aimed primarily at mechanization, sealing and dust removal of the technological process, at creating effective ventilation and providing workers with personal protective equipment against dust exposure. Regular medical examinations of workers are required. Preliminary medical examinations are carried out upon employment, 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 the general. ed. N. V. Lazareva, 6th ed., part 2, L., 1971.

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General information

Uniqueness arsenic is that it can be found everywhere - in rocks, minerals, water, soil, animals and plants. It is even called the omnipresent element. Arsenic is distributed over different geographical regions of the Earth due to the volatility of its compounds and their high solubility in water. If the climate of the region is humid, then the element is washed out of the ground and then carried away by groundwater. Surface waters and deep rivers contain from 3 µg/l to 10 µg/l of the substance, while sea and ocean water contains much less, about 1 µg/l.

Arsenic is found in the body of an adult in an amount of approximately 15 mg. Most of it is found in the liver, lungs, small intestine and epithelium. The absorption of the substance occurs in the stomach and intestines.
The antagonists of the substance are phosphorus, sulfur, selenium, vitamins E, C, as well as some amino acids. In turn, the substance impairs the body's absorption of selenium, zinc, vitamins A, E, C, folic acid.
The secret of its benefits is in its quantity: in a small dose, it performs a number of useful functions; and in large ones it is the strongest poison.

Functions:

• Improving the absorption of phosphorus and nitrogen.
• Stimulation of hematopoiesis.
• Weakening of oxidative processes.
• Interaction with proteins, lipoic acid, cysteine.

The daily requirement for this substance is small - from 30 to 100 mcg.

Arsenic as a chemical element

Arsenic is classified as a chemical element of group V of the periodic table and belongs to the nitrogen family. Under natural conditions, this substance is represented by the only stable nuclide. More than a dozen radioactive isotopes of arsenic have been artificially obtained, with a wide range of half-life values ​​- from a couple of minutes to a couple of months. The formation of the term is associated with its use for the extermination of rodents - mice and rats. Latin name Arsenicum (As) derived from the Greek word arsene", What means: powerful, strong.

Historical information

Arsenic in its purest form was discovered during alchemical experiments in the Middle Ages. And its compounds have been known to people for a long time, they were used for the production of medicines and paints. Today, arsenic is used in metallurgy in a particularly versatile way.

Historians called one of the periods of human development the Bronze Age. At this time, people switched from stone weapons to improved bronze weapons. Bronze is a compound ( alloy) tin with copper. According to historians, the first bronze was cast in the Tigris and Euphrates valley, around the 30th century. BC. Depending on the percentage composition of the components included in the alloy, bronze cast by different blacksmiths could have different properties. Scientists have found that the best bronze with valuable properties is an alloy of copper, which contains up to 3% tin and up to 7% arsenic substances. Such bronze was easily cast and better forged. Probably, during smelting, copper ore was confused with weathering products of copper-arsenic sulfide minerals, which had a similar appearance. The ancient masters appreciated the good properties of the alloy and then purposefully searched for deposits of arsenic minerals. To find them, they used the specific property of these minerals to give a garlic smell when heated. But over time, the smelting of bronze containing arsenic compounds ceased. Most likely, this happened due to the fact that poisoning very often occurred during the firing of arsenic-containing substances.

Of course, in the distant past, this element was known only in the form of its minerals. In ancient China, they knew a solid mineral called realgar, which, as is now known, is a sulfide of the composition As4S4. Word " realgar" in Arabic means " mine dust". This mineral was used for stone carving, but it had one significant drawback: in the light or when heated, the realgar "spoiled", because under the influence of a thermal reaction it turned into a completely different substance As2S3.

Scientist and philosopher Aristotle in the 4th c. BC. gave its name to this mineral - " sandarac". Three centuries later, the Roman scholar and writer Pliny the Elder together with a doctor and a botanist Dioscorides described another mineral called orpiment. The Latin name of the mineral is translated " gold paint". This mineral was used as a yellow dye.

In the Middle Ages, alchemists isolated three forms of the substance: yellow arsenic ( which is the sulfide As2S3), red ( sulfide As4S4) and white ( oxide As2O3). White is formed by the sublimation of some impurities of arsenic during the roasting of copper ores that contain this element. It condensed from the gas phase, and settled in the form of a white coating, after which it was collected.

In the 13th century, alchemists heated yellow arsenic and soap to produce a metal-like substance that may have been the first pure artificial substance. But the resulting substance violated the ideas of alchemists about the mystical "connection" of the seven metals known to them with seven astronomical objects - the planets; that is why the alchemists called the resulting substance "illegitimate metal." They noticed one interesting property behind him - the substance could give copper a white color.

Arsenic was clearly identified as an independent substance at the beginning of the 17th century, when an apothecary Johann Schroeder when reducing oxide with charcoal, I received it in its pure form. A few years later, a French physician and chemist Nicola Lemery managed to obtain this substance by heating its oxide in a mixture with potash and soap. In the next century, it was already well known and was called an unusual "half-metal".

Swedish scientist Scheele experimentally obtained arsenic gaseous hydrogen and arsenic acid. In the same time A.L. Lavoisier recognized this substance as an independent chemical element.

Being in natural conditions

The element is often found in natural conditions in compounds with copper, cobalt, nickel, and iron. There is not so much of it in the earth's crust - about 5 grams per ton, which is about the same as tin, molybdenum, germanium, tungsten and bromine.

The composition of the minerals that form a given chemical element ( today there are more than 200), due to the "semi-metallic" properties of the element. It can be in both negative and positive oxidation states and therefore easily combines with many other elements; in positive oxidation, arsenic plays the role of a metal ( for example, in sulfides), with a negative - non-metal ( in arsenides). Arsenic-containing minerals have a complex composition. The element itself can replace antimony, sulfur, and metal atoms in the crystal lattice.

Many compounds of metals and arsenic, judging by their composition, are rather intermetallic compounds than arsenides; some of them differ in the variable content of the main element. Several metals can be simultaneously present in arsenides, and the atoms of these metals, with a close ion radius, can replace each other in the crystal lattice in arbitrary proportions. All minerals classified as arsenides have a metallic luster. They are opaque, heavy, their hardness is low.

An example of natural arsenides ( there are approximately 25) can serve such minerals as skutterudite, saffflorite, rammelsbergite, nickelskutterudite, nickeline, lollingite, sperrylite, maucherite, algodonite, langisite, clinosafflorite. These arsenides have a high density and belong to the group of "superheavy" minerals.

The most common mineral is arsenopyrite ( or, as it is also called, arsenic pyrite). Of interest to chemists is the structure of those minerals in which arsenic is present simultaneously with sulfur, and in which it plays the role of a metal, since it is grouped together with other metals. These minerals are arsenosulvanite, girodite, arsenohauchecornite, freibergite, goldfieldite, tennantite, and argentotennantite. The structure of these minerals is very complex.

Such natural sulfides as realgar, orpiment, dimorphite, getchellite, have a positive oxidation state As ( lat. arsenic designation). These minerals look like small inclusions, although occasionally large crystals of large size and weight have been mined in some areas.

An interesting fact is that natural salts of arsenic acid, called arsenates, look very different. Erythrite has a cobalt color, scorodite, annabergite and simplesite are green. And gernesite, kettigit, rooseveltite are completely colorless.

In the central district of Sweden, there are quarries in which ferromanganese ore is mined. In these quarries, more than fifty samples of minerals that are arsenates have been found and described. Some of these arsenates were not found anywhere else. According to experts, these minerals were formed at low temperatures as a result of the interaction of arsenic acid with other substances. Arsenates are oxidation products of some sulfide ores. Usually they have no value other than aesthetic. Such minerals are decorations of mineralogical collections.

The names of minerals were given in different ways: some of them were named after scientists, prominent politicians; others were named after the locality in which they were found; still others were named after Greek terms denoting their main properties ( e.g. color); the fourth were called abbreviations denoting the initial letters of the names of other elements.

For example, the formation of the ancient name of such a mineral as nickeline is interesting. Previously, it was called kupfernikel. German miners working on copper five or six centuries ago were superstitiously afraid of an evil mountain spirit called Nickel. German word " kupfer" meant " copper". Kupfernickel they called "damn" or "fake" copper. This ore was very similar to copper, but copper could not be obtained from it. But it has found its application in glass-making. With its help, the glass was painted green. Subsequently, a new metal was isolated from this ore, and it was called nickel.

Pure arsenic is quite inert in its chemical properties and can be found in its native state. It looks like fused needles or cubes. Such a nugget is easy to grind into powder. It contains up to 15% impurities ( cobalt, iron, nickel, silver and other metals).

As a rule, the As content in the soil is from 0.1 mg/kg to 40 mg/kg. In those areas where arsenic ore occurs, and in the area of ​​volcanoes, the soil can contain a very large amount of As - up to 8 g/kg. It is this indicator that is found in some areas of New Zealand and Switzerland. In such areas, flora dies, and animals get sick. The same situation is typical for deserts and steppes, where arsenic is not washed out of the soil. Compared with the average content, clayey rocks are also considered enriched, since they contain four times more arsenic substances.

If a pure substance is converted into a volatile organoarsenic compound as a result of biomethylation, then it is carried out of the soil not only by water, but also by the wind. Biomethylation is the addition of a methyl group to form a C-As bond. This process is carried out with the participation of the substance methylcobalamin - a methylated derivative of vitamin B12. Biomethylation of As occurs both in sea water and in fresh water. This leads to the formation of such arsenic-organic compounds as methylarsonic and dimethylarsonic acids.

In those areas where there is no specific pollution, arsenic concentration is 0.01 µg/m3, and in industrial areas where power plants and factories are located, the concentration reaches the level of 1 µg/m3. In areas where industrial centers are located, arsenic precipitation is intense and amounts to 40 kg/sq. km per year.

Volatile compounds of arsenic, when their properties were not yet fully studied, brought people a lot of trouble. Mass poisonings were not uncommon even in the 19th century. But the doctors did not know the reasons for the poisoning. And the poisonous substance was contained in the green paint for the wallpaper and in the plaster. High humidity led to the formation of mold. Under the action of these two factors, volatile organoarsenic substances were formed.

There is an assumption that the process of formation of volatile organoarsenic derivatives could cause a delayed poisoning of the emperor Napoleon which led to his death. This assumption is based on the fact that 150 years after his death, traces of arsenic were found in his hair.

Arsenic substances are found in moderate amounts in some mineral waters. Generally accepted standards establish that the concentration of arsenic in medicinal mineral waters should not exceed 70 µg/l. In principle, even if the concentration of the substance is higher, then this can lead to poisoning only with constant long-term use.

Arsenic can be found in natural waters in various compounds and forms. Trivalent arsenic, for example, is many times more toxic than pentavalent arsenic.

Some seaweeds can accumulate arsenic to levels that are dangerous to humans. Such algae may well grow and even multiply in an acidic arsenic environment. In some countries they are used as pesticides ( against rats).

Chemical properties

Sometimes arsenic is called a metal, but in fact it is rather a non-metal. It does not form salts in combination with acids, but in itself it is an acid-forming substance. Therefore, it is also called semi-metal. Like phosphorus, arsenic can exist in different allotropic forms.

One of these forms is gray arsenic, a rather fragile substance. Its fracture has a bright metallic sheen ( therefore its second name is "metal arsenic"). The electrical conductivity of this semimetal is 17 times less than that of copper, but at the same time 3.6 times greater than that of mercury. The higher the temperature, the lower the electrical conductivity. This typical property of metals is also characteristic of this semimetal.

If arsenic vapors are cooled for a short time to a temperature of -196 degrees ( is the temperature of liquid nitrogen), you get a soft transparent yellow substance, resembling yellow phosphorus in appearance. The density of this substance is much lower than that of metallic arsenic. Yellow arsenic and arsenic pairs are composed of molecules that are shaped like a tetrahedron ( those. pyramid shape with four bases). Phosphorus molecules have the same shape.

Under the influence of ultraviolet radiation, as well as when heated, yellow arsenic instantly turns into gray; this reaction releases heat. If vapors condense in an inert atmosphere, then another form of this element is formed - amorphous. If arsenic vapor is deposited on glass, a mirror film is formed.

The structure of the electron outer shell of this element is the same as that of phosphorus and nitrogen. Arsenic, like phosphorus, can form three covalent bonds.

If the air is dry, then As has a stable form. From moist air, it fades and is covered with black oxide on top. When ignited, arsenic vapors easily burn with a blue flame.

As in its pure form is quite inert; alkalis, water and various acids that do not have oxidizing properties do not affect it in any way. If we take dilute nitric acid, then it will oxidize pure As to orthoarsenic acid, and if we take concentrated, it will oxidize to orthoarsenic acid.

As reacts with sulfur and halogens. In reactions with sulfur, sulfides of various compositions are formed.

Arsenic as a poison

All arsenic compounds are poisonous.

Acute poisoning with these substances is manifested by abdominal pain, diarrhea, vomiting, and CNS depression. The symptoms of intoxication with this substance are very similar to those of cholera. Therefore, in judicial practice, cases of the use of arsenic as a poison were often encountered earlier. The poisonous compound most successfully used for criminal purposes is arsenic trioxide.

In those areas where there is an excess of a substance in water and soil, it accumulates in the thyroid glands of people. As a result, they develop endemic goiter.

Arsenic poisoning

Symptoms of arsenic poisoning are manifested by a metallic taste in the mouth, vomiting, and severe pain in the abdomen. Later, convulsions or paralysis may occur. Poisoning can lead to death. The most commonly available and well-known antidote for arsenic intoxication is milk. The main protein in milk is casein. It forms an insoluble compound with arsenic, which is not absorbed into the blood.

Poisoning occurs:
1. When inhaling arsenic compounds in the form of dust ( most often in adverse working conditions).
2. By drinking poisoned water and food.
3. When using certain medicines. The excess of the substance is deposited in the bone marrow, lungs, kidneys, skin, intestinal tract. There is a large amount of evidence that inorganic arsenic compounds are carcinogenic. Long-term use of arsenic-poisoned water or medications can lead to low-grade skin cancer ( bowen's cancer) or hemangioendothelioma of the liver.

In acute poisoning, gastric lavage is required as first aid. In stationary conditions, hemodialysis is performed to clean the kidneys. For use in acute and chronic poisoning, Unitiol is used - a universal antidote. Additionally, antagonist substances are used: sulfur, selenium, zinc, phosphorus; and without fail introduce a complex of vitamins and amino acids.

Symptoms of overdose and deficiency

Possible signs of arsenic deficiency are manifested by a decrease in the concentration of triglycerides in the blood, increased fertility, deterioration in the development and growth of the body.

Arsenic is a highly toxic substance, a single dose of 50 mg can be fatal. An overdose is manifested by irritability, allergies, headache, dermatitis, eczema, conjunctivitis, depression of the respiratory function and nervous system, and liver dysfunction. An overdose of a substance increases the risk of developing cancer.

The source of the element is: plant and animal products, seafood, grains, cereals, tobacco, wine, and even drinking water.

You should not worry about getting this trace element into our diet - it is found in almost all products of animal and vegetable origin, it is not present except in the composition of refined sugar. With food, he comes to us in sufficient quantities. Foods that are especially rich in it, such as shrimp, lobsters, spiny lobsters - in order to avoid overdose, you should eat in moderation so as not to get an excessive amount of poison inside.

Arsenic compounds can enter the human body with mineral water, seafood, juices, grape wines, medicines, herbicides and pesticides. This substance accumulates mainly in the reticuloendothelial system, as well as in the lungs, skin, and kidneys. Insufficient daily intake of a substance in the body is considered 1 mcg / day. The toxicity threshold is approximately 20 mg.

A large amount of the element is found in fish oil and, oddly enough, in wines. In normal drinking water, the content of the substance is low and not hazardous to health - about 10 µg / l. Some regions of the world ( Mexico, Taiwan, India, Bangladesh) are notorious for having high levels of arsenic in their drinking water ( 1 mg/l), and therefore mass poisoning of citizens sometimes occurs there.

Arsenic prevents the body from losing phosphorus. Vitamin D is a regulatory factor in the course of phosphorus-calcium metabolism, and arsenic, in turn, regulates phosphorus metabolism.

It is also known that some of the forms of allergies develop due to a deficiency in the body of arsenic.

The trace element is used to increase appetite in anemia. For selenium poisoning, arsenic is an excellent antidote. Experimental studies in mice have shown that precisely calculated doses of the substance help to reduce the incidence of cancer.

With an increase in the concentration of an element in the soil or food, intoxication occurs. Severe intoxication can lead to such serious diseases as laryngeal cancer or leukemia. Moreover, the number of deaths will also increase.

It is known that 80% of the substance that enters the body with food is sent to the gastrointestinal tract and from there enters the bloodstream, and the remaining 20% ​​enters us through the skin and lungs.

A day after entering the body, more than 30% of the substance is excreted from it with urine and about 4% with feces. According to the classification, arsenic is classified as immunotoxic, conditionally essential, elements. It has been proven that the substance takes part in almost all important biochemical processes.

Arsenic in dentistry

This substance is often used to treat dental diseases such as caries. Caries begins with the fact that the lime salts of the tooth enamel begin to break down, and the weakened tooth is attacked by pathogens. Affecting the soft inner part of the tooth, microbes form a carious cavity.
If at this stage of the disease the carious cavity is cleaned and filled with filling material, then the tooth will remain “alive”. And if you let the process take its course, then the carious cavity reaches the tissue that contains the blood, nerve and lymphatic vessels. It's called the pulp.

Inflammation of the pulp develops, after which the only means of preventing further spread of the disease will be the removal of the nerve. It is for this manipulation that arsenic is needed.

The pulp is exposed with a dental instrument, a grain of paste containing arsenic acid is placed on it, and it practically instantly diffuses into the pulp. A day later, the tooth dies. Now the pulp can be removed completely painlessly, and the root canals and pulp chamber can be filled with a special antiseptic paste, and the tooth can be filled.

Arsenic in the treatment of leukemia

Arsenic is quite successfully used to treat a mild form of leukemia, as well as during the period of primary exacerbation, in which a sharp increase in the spleen and lymph nodes has not yet been observed. It reduces or even suppresses the pathological formation of leukocytes, stimulates red hematopoiesis and the release of erythrocytes to the periphery.

Getting arsenic

It is obtained as a by-product of the processing of lead, copper, cobalt and zinc ores, as well as in the extraction of gold. Some of the polymetallic ores contain up to 12% arsenic. If they are heated to 650 - 700 degrees, then in the absence of air, sublimation occurs. If heated in air, "white arsenic" is formed, which is a volatile oxide. It is subjected to condensation and heated with coal, during this reaction, arsenic is reduced. Obtaining this element is a harmful production.

Previously, before the development of ecology as a science, "white arsenic" was released into the atmosphere in large quantities, and subsequently it settled on trees and plants. The permissible concentration in the air is 0.003 mg/m3, while near industrial facilities the concentration reaches 200 mg/m3. Oddly enough, it is not the factories that produce arsenic that pollute the environment more, but power plants and non-ferrous metallurgy enterprises. Bottom sediments near copper smelters contain a large amount of the element - up to 10 g/kg.

Another paradox is that this substance is extracted in larger quantities than it is required. This is a rare occurrence in the metal mining industry. Surpluses have to be disposed of in large metal containers, hiding them in worked-out old mines.

A valuable industrial mineral is arsenopyrite. Large copper-arsenic deposits are found in Central Asia, Georgia, USA, Japan, Norway, Sweden; gold-arsenic - in the USA, France; arsenic-cobalt - in New Zealand, Canada; arsenic-tin - in England and Bolivia.

Determination of arsenic

A qualitative reaction to arsenic consists in the precipitation of yellow sulfides from hydrochloric acid solutions. Traces are determined by the Gutzeit method or the Marsh reaction: paper strips impregnated with HgCl2 change color to dark in the presence of arsine, which reduces sublimate to mercury.

In the last half century, a variety of sensitive analysis techniques have been developed ( spectrometry), thanks to which even a small amount of arsenic can be detected. If there is very little substance in the water, then pre-concentration of the samples is performed.

Some compounds are analyzed by the selective hydride method. This method consists in carrying out the selective reduction of the analyte to the volatile substance arsine. Volatile arsines are frozen out in a container cooled with liquid nitrogen. Then, by slowly heating the contents of the container, it is possible to ensure that different arsines evaporate separately from each other.

Industrial Application

About 98% of all mined arsenic is not used in its pure form. But its compounds have gained popularity and are used in various industries. Hundreds of tons of the substance are mined and used annually. It is added to the composition of bearing alloys to improve quality, is used to create cables and lead batteries to increase hardness, and is used in alloys with germanium or silicon in the manufacture of semiconductor devices. Arsenic is used as a dopant that imparts a certain type of conductivity to "classical" semiconductors.

Arsenic is a valuable material in non-ferrous metallurgy. When added to lead in an amount of 1%, the hardness of the alloy increases. If a little arsenic is added to the molten lead, then in the process of casting the shot, balls of spherical regular shape come out. The addition of copper enhances its strength, corrosion resistance and hardness. Thanks to this additive, the fluidity of copper is increased, which facilitates the process of wire drawing.

As is added to some grades of brass, bronze, printing alloys, babbits. But still, metallurgists are trying to exclude this additive from the production process, since it is very harmful to humans. Moreover, it is also harmful to metals, since the presence of arsenic in large quantities deteriorates the properties of many alloys and metals.

Oxides are used in glassmaking as glass brighteners. Even ancient glassblowers knew that white arsenic contributes to the opacity of glass. However, small additions of it, on the contrary, lighten the glass. Arsenic is still included in the formulation of some glasses, for example, the "Viennese" glass used to create thermometers.

Arsenic compounds are used as an antiseptic to protect against spoilage, as well as for preserving furs, skins, stuffed animals; to create antifouling paints for water transport; for wood impregnation.

The biological activity of some As derivatives interested agronomists, workers of the sanitary and epidemiological service, and veterinarians. As a result, arsenic-containing preparations were created, which were stimulants of productivity and growth; medicines for the prevention of livestock diseases; antihelminthics.

Landowners in ancient China treated rice crops with arsenic oxide to keep them free from fungal diseases and rats, and thus secure the crop. Now, due to the toxicity of arsenic-containing substances, their use in agriculture is limited.

The most important areas for the use of arsenic-containing substances are the production of microcircuits, semiconductor materials and fiber optics, film electronics, as well as the growth of special single crystals for lasers. In these cases, as a rule, gaseous arsine is used. Indium and gallium arsenides are used in the manufacture of diodes, transistors, and lasers.

In tissues and organs, the element is mainly found in the protein fraction, much less of it in the acid-soluble fraction, and only a small part of it is in the lipid fraction. It is a participant in redox reactions; without it, the oxidative breakdown of complex carbohydrates is impossible. It is involved in fermentation and glycolysis. Compounds of this substance are used in biochemistry as specific enzyme inhibitors that are needed to study metabolic reactions. It is necessary for the human body as a trace element.