Cadmium: effects on the human body. Heavy metal poisoning

Cadmium is a soft, malleable, but heavy metal of gray-silver color, a simple element of the periodic table. Its content in the earth's crust cannot be called high, but cadmium is one of the scattered elements: it is found in soil, sea water and even in the air (especially in cities). usually accompanies zinc minerals, although cadmium minerals also exist. However, most of them have no industrial significance. Cadmium does not form separate deposits and is released from waste ores after zinc, lead or copper have been smelted from them.

Properties of cadmium

Cadmium is well processed, rolled and polished. In dry air, cadmium reacts (burns) with oxygen only at high temperatures. Reacts with inorganic acids to form salts. Does not react with alkali solutions. In the molten state, it reacts with halogens, sulfur, tellurium, selenium, oxygen.
- Despite the fact that cadmium is present in trace amounts in all living organisms and participates in their metabolism, its vapors and vapors of its compounds are extremely toxic. For example, the concentration is 2.5 g / cc. m of cadmium oxide in the air kills in 1 minute. It is very dangerous to inhale air with dust or fumes containing cadmium,
- Cadmium has the ability to accumulate in the human body, in plants, mushrooms. In addition, cadmium compounds are carcinogenic.
- Cadmium is considered one of the most dangerous heavy metals, it is classified as a substance of the 2nd hazard class, as well as mercury and arsenic. It negatively affects the enzyme, hormonal, circulatory and central nervous system, disrupts phosphorus-calcium metabolism (destroys bones), therefore, when working with it, you must use chemical protection. In case of cadmium poisoning, urgent medical attention is required.

Application

Most of the cadmium mined is used for the production of anti-corrosion coatings. The cadmium coating creates a stronger and more flexible adhesion to the part than all others, therefore cadmium plating is used to protect against corrosion in particularly difficult conditions, for example, in contact with sea water, to protect electrical contacts.
- Highly demanded in the manufacture of accumulators and batteries.
- Used as a reagent for laboratory research.
- Almost a fifth of the resulting substance is used for the manufacture of pigments - cadmium salts.
- It is used to impart the desired properties to alloys. Alloys with cadmium are fusible (with lead, tin, bismuth), ductile, and refractory (with nickel, copper, zirconium), wear-resistant. Alloys are used to produce wires for power lines, brazing alloys for aluminum, bearings for large and powerful engines (ship, aircraft). Low-melting alloys are used for the manufacture of gypsum castings, glass and metal brazing, and in some fire extinguishers.
- A very important area of ​​application is the nuclear industry. Rods are produced from cadmium to control the rate of atomic reaction in a reactor, as well as protective screens against neutron radiation.
- It is a part of semiconductors, film solar cells, phosphors, stabilizers for PVC, dental fillings.
- Alloys with gold are used in jewelry. By varying the ratio of gold to cadmium, alloys of different shades, from yellow to greenish, can be obtained.
- Sometimes it is used in cryotechnics because of its high thermal conductivity at very low temperatures.
- Cadmium is able to accumulate in cancer cells, therefore it is used in some methods of anticancer therapy.

The store "PrimeChemicalsGroup" sells chemical protection products, chemical reagents for laboratory research, glassware and instruments for laboratory equipment and research. Buyers will be pleased with the democratic prices, delivery in Moscow and the region, excellent service.

The content of the article

CADMIUM(Cadmium) Cd, - chemical element of the II group of the Periodic system. Atomic number 48, relative atomic mass 112.41. Natural cadmium consists of eight stable isotopes: 106 Cd (1.22%), 108 Cd (0.88%), 110 Cd (12.39%), 111 Cd (12.75%), 112 Cd (24.07 %), 113 Cd (12.26%), 114 Cd (28.85%) and 116 Cd (7.58%). The oxidation state is +2, rarely +1.

Cadmium was discovered in 1817 by the German chemist Stromeyer Friedrich (1776–1835).

When checking zinc oxide produced by one of the Schoenebeck factories, it was suspected that it contains an impurity of arsenic. When the drug was dissolved in acid and passed through a solution of hydrogen sulfide, a yellow precipitate, similar to arsenic sulfides, precipitated; however, a more thorough examination showed that this element was absent. For a final conclusion, a sample of suspicious zinc oxide and other zinc preparations (including zinc carbonate) from the same factory were sent to Friedrich Stromeyer, who since 1802 held the Department of Chemistry at the University of Göttingen and the post of inspector general of Hanoverian pharmacies.

By calcining zinc carbonate, Stromeyer obtained an oxide, but not white, as it should have been, but yellowish. He assumed that the color was caused by an admixture of iron, but it turned out that there was no iron. Stromeyer fully analyzed the zinc preparations and found that the yellow color was due to a new element. It was named after the zinc ore in which it was found: the Greek word kadmeia, "cadmium earth" is the ancient name for smithsonite ZnCO 3. According to legend, this word comes from the name of the Phoenician Cadmus, who supposedly was the first to find zinc stone and noticed its ability to give copper (when smelted from ore) a golden color. The hero of ancient Greek mythology was also called: according to one of the legends, Cadmus defeated the Dragon in a difficult duel and built the fortress of Cadmeus on its lands, around which the seven-fold city of Thebes then grew.

The abundance of cadmium in nature and its industrial extraction.

The cadmium content in the earth's crust is 1.6 · 10 -5%. It is close in prevalence to antimony (2 · 10 –5%) and twice as common as mercury (8 · 10 –6%). Cadmium is characterized by migration in hot groundwater together with zinc and other chemical elements prone to the formation of natural sulfides. It concentrates in hydrothermal deposits. Volcanic rocks contain up to 0.2 mg of cadmium per kg, among sedimentary rocks the richest in cadmium are clays - up to 0.3 mg / kg, to a lesser extent - limestones and sandstones (about 0.03 mg / kg). The average content of cadmium in the soil is 0.06 mg / kg.

Cadmium has its own minerals - greenockite CdS, otavite CdCO 3, monteponite CdO. However, they do not form their own deposits. The only industrially significant source of cadmium is zinc ores, where it is contained in a concentration of 0.01–5%. Cadmium also accumulates in galena (up to 0.02%), chalcopyrite (up to 0.12%), pyrite (up to 0.02%), stannite (up to 0.2%). The total world resources of cadmium are estimated at 20 million tons, industrial resources - at 600 thousand tons.

Characterization of a simple substance and industrial production of metallic cadmium.

Cadmium is a silvery solid with a bluish sheen on a fresh surface, soft, malleable, ductile metal, rolls well into sheets, and is easy to polish. Like tin, cadmium sticks make a crackling sound when bent. It melts at 321.1 ° C, boils at 766.5 ° C, density - 8.65 g / cm 3, which allows it to be classified as a heavy metal.

In dry air, cadmium is stable. In humid air, it quickly fades, and when heated, it easily interacts with oxygen, sulfur, phosphorus and halogens. Cadmium does not react with hydrogen, nitrogen, carbon, silicon and boron.

Cadmium vapors interact with water vapor to release hydrogen. Acids dissolve cadmium to form salts of this metal. Cadmium reduces ammonium nitrate in concentrated solutions to ammonium nitrite. It is oxidized in aqueous solution by cations of some metals, such as copper (II) and iron (III). Unlike zinc, cadmium does not interact with alkali solutions.

The main sources of cadmium are intermediate products of zinc production. Metal precipitates obtained after purification of zinc sulfate solutions by the action of zinc dust contain 2–12% cadmium. The fractions formed during the distillation of zinc contain 0.7-1.1% cadmium, and in the fractions obtained during the rectification purification of zinc - up to 40% cadmium. Cadmium is also extracted from the dust of lead and copper smelters (it can contain up to 5% and 0.5% cadmium, respectively). The dust is usually treated with concentrated sulfuric acid and then the cadmium sulfate is leached with water.

A cadmium sponge is precipitated from cadmium sulfate solutions by the action of zinc dust, then it is dissolved in sulfuric acid and the solution is purified from impurities by the action of zinc oxide or sodium carbonate, as well as by ion exchange methods. Metallic cadmium is isolated by electrolysis on aluminum cathodes or by reduction with zinc.

To remove zinc and lead, cadmium metal is remelted under an alkali layer. The melt is treated with aluminum to remove nickel and ammonium chloride to remove thallium. Using additional methods of purification, it is possible to obtain cadmium with an impurity content of 10–5% by weight.

About 20 thousand tons of cadmium are produced annually. The volume of its production is largely related to the scale of zinc production.

The most important area of ​​application of cadmium is the production of chemical current sources. Cadmium electrodes are used in batteries and accumulators. Nickel cadmium battery negative plates are made of iron meshes with sponge cadmium as the active agent. The positive plates are coated with nickel hydroxide. The electrolyte is a potassium hydroxide solution. Compact batteries for guided missiles are also made on the basis of cadmium and nickel, only in this case, not iron, but nickel nets are installed as a base.

The processes taking place in a nickel-cadmium alkaline battery can be described by the general equation:

Cd + 2NiO (OH) + 2H 2 O Cd (OH) 2 + 2Ni (OH) 2

Nickel-cadmium alkaline batteries are more reliable than lead (acid) batteries. These power sources are distinguished by high electrical characteristics, stability of operation, and long service life. They can be charged in just one hour. However, nickel-cadmium batteries cannot be recharged without full pre-discharge (they are inferior to metal hydride batteries in this regard).

Cadmium is widely used for the application of anti-corrosion coatings to metals, especially in cases of their contact with sea water. The most important parts of ships, airplanes, as well as various products intended for work in tropical climates are cadmized. Previously, iron and other metals were cadmium plated by immersing products in molten cadmium, now cadmium coating is applied electrolytically.

Cadmium coatings have several advantages over zinc coatings: they are more resistant to corrosion, and easier to make even and smooth. The high plasticity of such coatings ensures the tightness of threaded connections. In addition, cadmium, unlike zinc, is stable in an alkaline environment.

However, cadmium plating has its own problems. When cadmium is electrolytically applied to a steel part, hydrogen contained in the electrolyte can penetrate into the metal. It causes so-called hydrogen brittleness in high-strength steels, which leads to unexpected metal fracture under stress. To prevent this phenomenon, titanium is added to the cadmium coatings.

Moreover, cadmium is toxic. Therefore, although cadmium plate is used quite widely, it is prohibited to use it for the manufacture of kitchen utensils and food containers.

About a tenth of the world's cadmium production is spent on alloy production. Cadmium alloys are mainly used as antifriction materials and solders. The alloy containing 99% cadmium and 1% nickel is used for the manufacture of bearings operating in automobile, aircraft and marine engines at high temperatures. Since cadmium is not sufficiently resistant to acids, including organic acids contained in lubricants, sometimes cadmium-based bearing alloys are coated with indium.

Alloying copper with small additions of cadmium makes it possible to make wires on electric transport lines more wear-resistant. Copper with the addition of cadmium almost does not differ in electrical conductivity from pure copper, but it noticeably surpasses its strength and hardness.

Cadmium is included in Wood's metal, which contains 50% bismuth, 25% lead, 12.5% ​​tin, 12.5% ​​cadmium. Wood's alloy can be melted in boiling water. Curiously, the first letters of the components of Wood's alloy form the abbreviation WAX. It was invented in 1860 by the not very famous English engineer B. Wood. This invention is often mistakenly attributed to his namesake - the famous American physicist Robert Williams Wood, who was born only eight years later. Low-melting cadmium alloys are used as material for thin and complex castings, in automatic fire-fighting systems, for glass-to-metal soldering Solders containing cadmium are quite resistant to temperature fluctuations.

A sharp jump in demand for cadmium began in the 1940s and was associated with the use of cadmium in the nuclear industry - it turned out that it absorbs neutrons and began to make control and emergency rods of nuclear reactors from it. The ability of cadmium to absorb neutrons of strictly defined energies is used in the study of the energy spectra of neutron beams.

Cadmium compounds.

Cadmium forms binary compounds, salts and numerous complex, including organometallic, compounds. In solutions, the molecules of many salts, in particular halides, are associated. Solutions have a weakly acidic environment due to hydrolysis. Under the action of alkali solutions, starting from pH 7–8, basic salts precipitate.

Cadmium oxide CdO is obtained by the interaction of simple substances or by calcining cadmium hydroxide or carbonate. Depending on the "thermal history", it can be greenish yellow, brown, red, or nearly black. This is partly due to particle size, but is largely the result of lattice defects. Above 900 ° C, cadmium oxide is volatile, and at 1570 ° C it completely sublimes. It has semiconducting properties.

Cadmium oxide is readily soluble in acids and poorly in alkalis; it is easily reduced by hydrogen (at 900 ° C), carbon monoxide (above 350 ° C), carbon (above 500 ° C).

Cadmium oxide is used as an electrode material. It is a part of lubricating oils and mixtures for obtaining special glasses. Cadmium oxide catalyzes a number of hydrogenation and dehydrogenation reactions.

Cadmium hydroxide Cd (OH) 2 precipitates out as a white precipitate from aqueous solutions of cadmium (II) salts upon addition of alkali. When exposed to very concentrated alkali solutions, it is converted to hydroxocadmates such as Na 2. Cadmium hydroxide reacts with ammonia to form soluble complexes:

Cd (OH) 2 + 6NH 3 H 2 O = (OH) 2 + 6H 2 O

In addition, cadmium hydroxide goes into solution under the action of alkali cyanides. Above 170 ° C, it decomposes to cadmium oxide. The interaction of cadmium hydroxide with hydrogen peroxide in an aqueous solution leads to the formation of peroxides of various compositions.

Cadmium hydroxide is used to obtain other cadmium compounds, as well as an analytical reagent. It is part of cadmium electrodes in power supplies. In addition, cadmium hydroxide is used in decorative glasses and enamels.

Cadmium fluoride CdF 2 is slightly soluble in water (4.06% by weight at 20 ° C), insoluble in ethanol. It can be obtained by the action of fluorine on a metal or hydrogen fluoride on cadmium carbonate.

Cadmium fluoride is used as an optical material. It is included in some glasses and phosphors, as well as solid electrolytes in chemical current sources.

Cadmium chloride CdCl 2 is readily soluble in water (53.2% by weight at 20 ° C). Its covalent nature is responsible for a relatively low melting point (568.5 ° C), as well as solubility in ethanol (1.5% at 25 ° C).

Cadmium chloride is obtained by reacting cadmium with concentrated hydrochloric acid or by chlorination of a metal at 500 ° C.

Cadmium chloride is a component of electrolytes in cadmium galvanic cells and sorbents in gas chromatography. It is a part of some solutions in photography, catalysts in organic synthesis, fluxes for growing semiconductor crystals. It is used as a mordant for dyeing and printing fabrics. Organo cadmium compounds are obtained from cadmium chloride.

Cadmium bromide CdBr 2 forms scaly crystals with a pearlescent sheen. It is very hygroscopic, readily soluble in water (52.9% by weight at 25 ° C), methanol (13.9% by weight at 20 ° C), ethanol (23.3% by weight at 20 ° C).

Cadmium bromide is obtained by metal bromination or by the action of hydrogen bromide on cadmium carbonate.

Cadmium bromide serves as a catalyst in organic synthesis, is a stabilizer for photographic emulsions and a component of virulent compositions in photography.

Cadmium iodide CdI 2 forms shiny, leafy crystals with a layered (two-dimensional) crystal structure. Up to 200 polytypes of cadmium iodide are known, differing in the sequence of arrangement of layers with hexagonal and cubic closest packing.

Unlike other halogens, cadmium iodide is not hygroscopic. It dissolves well in water (46.4% by weight at 25 ° C). Cadmium iodide is obtained by metal iodide by heating or in the presence of water, as well as by the action of hydrogen iodide on cadmium carbonate or oxide.

Cadmium iodide serves as a catalyst in organic synthesis. It is a component of pyrotechnic compositions and lubricants.

Cadmium sulphide CdS was probably the first compound of this element that the industry became interested in. It forms crystals from lemon yellow to orange-red in color. Cadmium sulfide has semiconducting properties.

This compound is practically insoluble in water. It is also resistant to the action of solutions of alkalis and most acids.

Cadmium sulfide is obtained by the interaction of cadmium and sulfur vapors, precipitation from solutions under the action of hydrogen sulfide or sodium sulfide, reactions between cadmium and organosulfur compounds.

Cadmium sulfide is an important mineral colorant; it was previously called cadmium yellow.

In the painting business, cadmium yellow later became more widely used. In particular, it was used to paint passenger cars, because, among other advantages, this paint resisted steam locomotive smoke well. Cadmium sulfide was also used as a dye in the textile and soap industries. The corresponding colloidal dispersions were used to obtain colored transparent glasses.

V last years pure cadmium sulfide is being replaced by cheaper pigments - cadmopon and zinc-cadmium lithopone. Cadmopon is a mixture of cadmium sulfide and barium sulfate. It is obtained by mixing two soluble salts - cadmium sulfate and barium sulfide. The result is a precipitate containing two insoluble salts:

CdSO 4 + BaS = CdSЇ + BaSO 4 Ї

Zinc-cadmium lithopone also contains zinc sulfide. In the manufacture of this dye, three salts precipitate simultaneously. Lithopon is cream or ivory.

With the addition of cadmium selenide, zinc sulfide, mercury sulfide and other compounds, cadmium sulfide gives thermally stable pigments with a bright color from pale yellow to dark red.

Cadmium sulfide imparts a blue color to the flame. This property is used in pyrotechnics.

In addition, cadmium sulfide is used as an active medium in semiconductor lasers. It happens as a material for the manufacture of photocells, solar cells, photodiodes, LEDs, phosphors.

Cadmium selenide CdSe forms dark red crystals. It does not dissolve in water, decomposes with hydrochloric, nitric and sulfuric acids. Cadmium selenide is obtained by fusing simple substances or from gaseous cadmium and selenium, as well as by precipitation from a solution of cadmium sulfate under the action of hydrogen selenide, the reaction of cadmium sulfide with selenous acid, and the interaction between cadmium and organoselenium compounds.

Cadmium selenide is a phosphor. It serves as an active medium in semiconductor lasers, is a material for the manufacture of photoresistors, photodiodes, solar cells.

Cadmium selenide is a pigment for enamels, glazes and artistic paints. Ruby glass is stained with cadmium selenide. It was he, and not chromium oxide, as in the ruby ​​itself, that made the stars of the Moscow Kremlin ruby-red.

Cadmium telluride CdTe can be dark gray to dark brown in color. It does not dissolve in water, but decomposes with concentrated acids. It is obtained by the interaction of liquid or gaseous cadmium and tellurium.

Cadmium telluride, which has semiconducting properties, is used as an X-ray and gamma-ray detector, and mercury-cadmium telluride has found wide application (especially for military purposes) in infrared detectors for thermal imaging.

In case of violation of stoichiometry or the introduction of impurities (for example, copper and chlorine atoms), cadmium telluride acquires photosensitive properties. It is used in electrophotography.

Organic cadmium compounds CdR 2 and CdRX (R = CH 3, C 2 H 5, C 6 H 5 and other hydrocarbon radicals, X are halogens, OR, SR, etc.) are usually obtained from the corresponding Grignard reagents. They are less thermally stable than their zinc counterparts, but are generally less reactive (usually not flammable in air). Their most important field of application is the production of ketones from acid chlorides.

The biological role of cadmium.

Cadmium is found in the organisms of almost all animals (in terrestrial animals it is about 0.5 mg per 1 kg of weight, and in marine animals - from 0.15 to 3 mg / kg). At the same time, it is classified as one of the most toxic heavy metals.

Cadmium is concentrated in the body mainly in the kidneys and liver, while the content of cadmium in the body increases with old age. It accumulates in the form of complexes with proteins that are involved in enzymatic processes. Getting into the body from the outside, cadmium has an inhibitory effect on a number of enzymes, destroying them. Its action is based on binding of the –SH group of cysteine ​​residues in proteins and inhibition of SH enzymes. It can also inhibit the action of zinc-containing enzymes by displacing zinc. Due to the closeness of the ionic radii of calcium and cadmium, it can replace calcium in bone tissue.

People are poisoned with cadmium by consuming water contaminated with cadmium-containing waste, as well as vegetables and grains growing on lands located near oil refineries and metallurgical enterprises. Mushrooms have a special ability to accumulate cadmium. According to some reports, the content of cadmium in mushrooms can reach units, tens and even 100 or more milligrams per kg of their own weight. Cadmium compounds are among the harmful substances in tobacco smoke (one cigarette contains 1-2 μg of cadmium).

A classic example of chronic cadmium poisoning is a disease first described in Japan in the 1950s and called itai-itai. The disease was accompanied by severe pain in the lumbar region, muscle pain. There were also characteristic signs of irreversible kidney damage. Hundreds of itai-itai deaths have been recorded. The disease became widespread due to the high environmental pollution in Japan at that time and the specifics of the Japanese diet - mainly rice and seafood (they are able to accumulate cadmium in high concentrations). Studies have shown that those affected by itai-itai consumed up to 600 mcg of cadmium per day. Subsequently, as a result of environmental protection measures, the frequency and severity of syndromes like “itai-itai” decreased markedly.

In the United States, a relationship was found between atmospheric cadmium and the frequency of deaths from cardiovascular disease.

It is believed that about 1 μg of cadmium per 1 kg of its own weight can enter the human body per day without harm to health. Drinking water should not contain more than 0.01 mg / l of cadmium. The antidote for cadmium poisoning is selenium, but the use of foods rich in this element leads to a decrease in the sulfur content in the body, in which case cadmium becomes dangerous again.

Elena Savinkina

Cadmium

CADMIUM-I am; m.[lat. cadmium from Greek. kadmeia - zinc ore]

1. A chemical element (Cd), a silvery-white soft, viscous metal contained in zinc ores (it is part of many low-melting alloys, used in the nuclear industry).

2. Artificial yellow paint in different shades.

◁ Cadmium, th, th. K-th alloys. K-th yellow(dye).

(lat. Cadmium), chemical element of group II of the periodic system. The name is from the Greek kadméia - zinc ore. A silvery metal with a bluish sheen, soft and fusible; density 8.65 g / cm 3, t pl 321.1ºC. They are mined during the processing of lead-zinc and copper ores. They are used for cadmium plating, in high-power accumulators, in nuclear power engineering (control rods of reactors), for the production of pigments. It is a part of low-melting and other alloys. Cadmium sulfides, selenides and tellurides are semiconducting materials. Many cadmium compounds are poisonous.

Cadmium (lat. Cadmium), Cd (read "cadmium"), a chemical element with atomic number 48, atomic mass 112.41.
Natural cadmium consists of eight stable isotopes: 106 Cd (1.22%), 108 Cd (0.88%), 110 Cd (12.39%), 111 Cd (12.75%), 112 Cd (24.07 %), 113 Cd (12.26%), 114 Cd (28.85%) and 116 Cd (12.75%). Located in the 5th period in group IIB of the periodic table of elements. Configuration of the two outer electronic layers 4 s 2 p 6 d 10 5s 2 ... Oxidation state +2 (valence II).
The radius of the atom is 0.154 nm, the radius of the Cd 2+ ion is 0.099 nm. The sequential ionization energies are 8.99, 16.90, 37.48 eV. Pauling electronegativity (cm. POLING Linus) 1,69.
Discovery history
Discovered by the German professor F. Stromeyer (cm. STROMEIER Friedrich) in 1817. Pharmacists of Magdeburg in the study of zinc oxide (cm. ZINC (chemical element)) ZnO was suspected of arsenic impurity (cm. ARSENIC)... F. Stromeyer isolated brown-brown oxide from ZnO, reduced it with hydrogen (cm. HYDROGEN) and received a silvery-white metal, which was named cadmium (from the Greek kadmeia - zinc ore).
Being in nature
Content in the earth's crust is 1.35 · 10 -5% by weight, in the water of seas and oceans 0.00011 mg / l. Several very rare minerals are known, for example, greenockite GdS, otavite CdCO 3, monteponite CdO. Cadmium accumulates in polymetallic ores: sphalerite (cm. SPHALERITE)(0.01-5%), galena (cm. GALENA)(0.02%), chalcopyrite (cm. HALCOPIRITE)(0.12%), pyrite (cm. PYRITE)(0.02%), fahlores (cm. BLUE ORE) and stannina (cm. STANNIN)(up to 0.2%).
Receiving
The main sources of cadmium are intermediate products of zinc production, dust from lead and copper smelters. The raw material is treated with concentrated sulfuric acid and CdSO 4 is obtained in solution. Cd is isolated from the solution using zinc dust:
CdSO 4 + Zn = ZnSO 4 + Cd
The resulting metal is purified by remelting under a layer of alkali to remove zinc and lead impurities. High-purity cadmium is obtained by electrochemical refining with intermediate purification of the electrolyte or by zone melting (cm. ZONE MELT).
Physical and chemical properties
Cadmium is a silvery white soft metal with a hexagonal lattice ( a = 0,2979, with= 0.5618 nm). Melting point 321.1 ° C, boiling point 766.5 ° C, density 8.65 kg / dm 3. If the cadmium stick is bent, then you can hear a faint crackling - it is the metal microcrystals rubbing against each other. Standard electrode potential of cadmium -0.403 V, in the range of standard potentials (cm. STANDARD CAPACITY) it is located before hydrogen (cm. HYDROGEN).
In a dry atmosphere, cadmium is stable, in a humid atmosphere it gradually becomes covered with a film of CdO oxide. Above the melting point, cadmium burns in air with the formation of brown CdO oxide:
2Cd + O 2 = 2CdO
Cadmium vapors react with water vapor to form hydrogen:
Cd + H 2 O = CdO + H 2
Compared to its neighbor in group IIB - Zn, cadmium reacts more slowly with acids:
Сd + 2HCl = CdCl 2 + H 2
The reaction proceeds most easily with nitric acid:
3Cd + 8HNO 3 = 3Cd (NO 3) 2 + 2NO - + 4H 2 O
Cadmium does not react with alkalis.
In reactions, it can act as a mild reducing agent, for example, in concentrated solutions, it is able to reduce ammonium nitrate to NH 4 NO 2 nitrite:
NH 4 NO 3 + Cd = NH 4 NO 2 + CdO
Cadmium is oxidized by solutions of Cu (II) or Fe (III) salts:
Cd + CuCl 2 = Cu + CdCl 2;
2FeCl 3 + Cd = 2FeCl 2 + CdCl 2
Above the melting point, cadmium reacts with halogens (cm. HALOGENS) with the formation of halides:
Cd + Cl 2 = CdCl 2
With gray (cm. SULFUR) and other chalcogenes forms chalcogenides:
Cd + S = CdS
Cadmium does not react with hydrogen, nitrogen, carbon, silicon and boron. Cd 3 N 2 nitride and CdH 2 hydride are obtained indirectly.
In aqueous solutions, cadmium ions Cd 2+ form aqua complexes 2+ and 2+.
Cadmium hydroxide Cd (OH) 2 is obtained by adding alkali to the cadmium salt solution:
СdSO 4 + 2NaOH = Na 2 SO 4 + Cd (OH) 2 Ї
Cadmium hydroxide practically does not dissolve in alkalis, although during prolonged boiling in very concentrated alkali solutions, the formation of hydroxide complexes 2– is recorded. Thus, amphoteric (cm. AMPHOTHERIC) the properties of cadmium oxide CdO and hydroxide Cd (OH) 2 are much weaker than those of the corresponding zinc compounds.
Cadmium hydroxide Cd (OH) 2, due to complexation, easily dissolves in aqueous solutions of ammonia NH 3:
Cd (OH) 2 + 6NH 3 = (OH) 2
Application
40% of the cadmium produced is used for the application of anti-corrosion coatings to metals. 20% of cadmium goes to the manufacture of cadmium electrodes used in batteries, normal Weston cells. About 20% of cadmium is used for the production of inorganic dyes, special solders, semiconductor materials and phosphors. 10% cadmium is a component of jewelry and low-melting alloys, plastics.
Physiological action
Vapors of cadmium and its compounds are toxic, and cadmium can accumulate in the body. In drinking water, the maximum permissible concentration for cadmium is 10 mg / m 3. Symptoms of acute poisoning with cadmium salts are vomiting and convulsions. Soluble cadmium compounds, after being absorbed into the blood, affect the central nervous system, liver and kidneys, and disrupt phosphorus-calcium metabolism. Chronic poisoning leads to anemia and bone destruction.

encyclopedic Dictionary. 2009 .

See what "cadmium" is in other dictionaries:

- (lat.cadmium). A viscous metal, similar in color to tin. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. CADMIUS lat. cadmium, from kadmeia gea, cadmium earth. A metal that looks like tin. Explanation of 25,000 foreign ... ... Dictionary of foreign words of the Russian language

CADMIUM- CADMIUM, Cadmium, chem. element, char. Cd, atomic weight 112.41, serial number 48. It is contained in small quantities in most zinc ores and is obtained as a by-product when zinc is mined; can also be obtained ... ... Great medical encyclopedia

CADMIUM- see CADMIUM (Cd). Contained in the branch waters of many industrial enterprises, especially lead-zinc and metal-working plants using electroplating. It is present in phosphate fertilizers. Sulfuric acid dissolves in water, ... ... Fish Diseases: A Handbook

Cadmium- (Cd) silvery white metal. It is used in nuclear power engineering and electroplating, is a part of alloys, is used for the preparation of printing plates, solders, welding electrodes, in the production of semiconductors; is a component ... ... Russian encyclopedia of labor protection

- (Cadmium), Cd, chemical element of group II of the periodic system, atomic number 48, atomic mass 112.41; metal, m.p. 321.1shC. Cadmium is used for applying anti-corrosion coatings on metals, making electrodes, obtaining pigments, ... ... Modern encyclopedia

- (symbol Cd), a silvery white metal from the second group of the periodic table. First isolated in 1817. Contained in greenockite (in the form of sulfide), but it is mainly obtained as a by-product in the extraction of zinc and lead. Easy to forge ... Scientific and technical encyclopedic dictionary

Cd (from the Greek kadmeia zinc ore * a. Cadmium; n. Kadmium; f. Cadmium; and. Cadmio), chem. element of group II periodic. Mendeleev system, at.n. 48, at. m. 112.41. In nature, there are 8 stable isotopes 106Cd (1.225%) 108Cd (0.875%), ... ... Geological encyclopedia

Husband. metal (one of the chemical principles or non-degradable elements) found in zinc ore. Cadmium, related to cadmium. Admisty containing cadmium. Dahl's Explanatory Dictionary. IN AND. Dahl. 1863 1866 ... Dahl's Explanatory Dictionary

Cadmium- (Cadmium), Cd, chemical element of group II of the periodic system, atomic number 48, atomic mass 112.41; metal, m.p. 321.1 ° C. Cadmium is used for applying anti-corrosion coatings on metals, making electrodes, obtaining pigments, ... ... Illustrated Encyclopedic Dictionary

CADMIUM- chem. element, symbol Cd (Latin Cadmium), at. n. 48, at. m. 112.41; silvery white shiny soft metal, density 8650 kg / m3, melting point = 320.9 ° С. Cadmium is a rare and trace element, poisonous, usually found in ores together with zinc, for which ... ... Big Polytechnic Encyclopedia

- (lat. Cadmium) Cd, chemical element of group II of the periodic system, atomic number 48, atomic mass 112.41. The name is from the Greek kadmeia zinc ore. A silvery metal with a bluish sheen, soft and fusible; density 8.65 g / cm & sup3, ... ... Big Encyclopedic Dictionary

What is Cadmium? It is a heavy metal that is obtained from the smelting of other metals such as zinc, copper or lead. It is widely used to make nickel-cadmium batteries. In addition, cigarette smoke also contains such an element. As a result of continuous exposure to cadmium, very serious diseases of the lungs and kidneys occur. Let's consider the features of this metal in more detail.

Scope of application of cadmium

Most of the industrial use of this metal is in protective coatings that protect metals from corrosion. Such a coating has a great advantage over zinc, nickel or tin, because it does not peel off during deformation.

What other uses for cadmium can there be? It is used to produce alloys that are remarkably machinable. Cadmium alloys with minor additions of copper, nickel and silver are used for the manufacture of bearings for automobile, aircraft and marine engines.

Where else is cadmium used?

Welders, metallurgists and workers associated with the textile, electronics and battery industries are the most at risk of cadmium poisoning. Nickel-cadmium batteries are used in mobile phones and other electronic devices. This metal is also used in the production of plastics, paints, metal coatings. Many soils that are regularly fertilized can also contain high levels of this toxic metal.

cadmium: properties

Cadmium, as well as its compounds, are characterized as, but it has not been proven that a small amount of the element in environment causes cancer. Inhalation of metal particles in industrial production does contribute to the development of lung cancer, but when they eat contaminated food, they do not pose a risk of developing cancer.

How does cadmium enter the human body?

Everyone has known for a long time that cigarette smoke contains cadmium. This heavy metal enters the body of a smoker in an amount twice as much as that of a person who is not subject to such a bad habit. However, secondhand smoke can be harmful.

Leafy vegetables, grains and potatoes grown in soils high in cadmium can pose a threat. The liver and kidneys of marine life and animals are also famous for the increased content of this metal.

Many industrial enterprises, especially metallurgical ones, emit large amounts of cadmium into the atmosphere. People living near such enterprises are automatically included in the risk group.

Some agricultural areas actively use phosphate fertilizers, which contain trace amounts of cadmium. Products grown on this land pose a potential threat to humans.

The effect of cadmium on the human body

Thus, we have sorted out what cadmium is. The impact on the human body of this heavy metal can cause negative consequences. In any living organism, it is found in an insignificant amount, and its biological role is still not fully understood. Usually cadmium is associated with negative function.

Its toxic effect is based on blocking sulfur-containing amino acids, which leads to disruption of protein metabolism and damage to the cell nucleus. This heavy metal promotes the removal of calcium from the bones and damages the nervous system. It can accumulate in the kidneys and liver, and it is excreted from the body very slowly. This process can take decades. Usually, cadmium is excreted in urine and feces.

Inhalation of cadmium

This element is absorbed into the body of industrial workers by inhalation. To prevent this, use effective protective equipment. Disregard of this rule leads to sad consequences. If cadmium is inhaled, the effect of such a metal on the human body is manifested as follows: the body temperature rises, chills and muscle pain appear.

After a while, lung damage occurs, chest pain, shortness of breath, and coughing occur. In severe cases, this condition causes the death of the patient. Inhalation of air containing cadmium contributes to the development of kidney disease and osteoporosis. The likelihood of lung cancer increases several times.

Intake of cadmium with food

Why is cadmium in water and food dangerous? With the regular use of contaminated foods and water, this metal begins to accumulate in the body, which leads to negative consequences: kidney function is disrupted, bone tissue is weakened, liver and heart are affected, and in severe cases death occurs.

Eating foods contaminated with cadmium can cause stomach irritation, nausea, abdominal pain, diarrhea, and vomiting. In addition, flu-like symptoms appear, laryngeal edema develops and tingling in the hands occurs.

Causes of cadmium poisoning

Heavy metal poisoning most often occurs in children, diabetics, pregnant and lactating women, people who abuse smoking. In Japan, cadmium intoxication occurs as a result of eating contaminated rice. In this case, apathy develops, kidneys are affected, bones soften and deform.

Industrialized regions, where oil refineries and metallurgical enterprises are located, are famous for the fact that the soil there is contaminated with cadmium. If plant products are grown in such places, then there is a high probability that heavy metal poisoning will occur.

The element can accumulate in large quantities in tobacco. If the raw material is dried, then the metal content rises sharply. The intake of cadmium into the body occurs both with active and with the occurrence of lung cancer directly depends on the content of metal in the smoke.

Treatment for poisoning

Cadmium:

• damage to the central nervous system;
• sharp bone pain;
• protein in the urine;
• stones in the kidneys;
• dysfunction of the genitals.

If acute poisoning occurs, the victim should be kept warm, he needs to provide an influx of fresh air and rest. After washing the stomach, he needs to be given warm milk, to which a little baking soda is added. There are no antidotes for cadmium. Unithiol, steroids and diuretics are used to neutralize the metal. Complex treatment involves the use of cadmium antagonists (zinc, iron, selenium, vitamins). The doctor may prescribe a general tonic diet that is high in fiber and pectin.

Possible consequences

A metal such as cadmium has a very serious effect on the human body, and if poisoning with this element occurs, the consequences can be dangerous. It displaces calcium from the bones, contributing to the development of osteoporosis. In adults and children, the spine begins to bend and bone deformation occurs. In childhood, such poisoning leads to encephalopathy and neuropathy.

Output

Thus, we have sorted out what a heavy metal like cadmium is. The influence of this element on the human body is quite serious. Gradually accumulating in the body, it leads to the destruction of many organs. You can even get poisoned with cadmium if you eat a lot of contaminated foods. The consequences of poisoning are also quite dangerous.

DEFINITION

Cadmium- the forty-eighth element of the Periodic Table. Designation - Cd from the Latin "cadmium". Located in the fifth period, IIB group. Refers to metals. The core has a charge of 48.

In terms of its properties, cadmium is similar to zinc and is usually found as an impurity in zinc ores. In terms of prevalence in nature, it is significantly inferior to zinc: the cadmium content in the earth's crust is only about 10 -5% (wt.).

Cadmium is a silvery white (Fig. 1) soft, malleable, ductile metal. In the series of voltages, it stands farther than zinc, but ahead of hydrogen and displaces the last of the acids. Since Cd (OH) 2 is a weak electrolyte, cadmium salts are hydrolyzed and their solutions are acidic.

Rice. 1. Cadmium. Appearance.

Atomic and molecular weight of cadmium

Relative molecular weight of the substance(M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms of a chemical element is more than 1/12 of the mass of a carbon atom.

Since in the free state cadmium exists in the form of monatomic Cd molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 112.411.

Cadmium isotopes

It is known that in nature, cadmium can be in the form of eight stable isotopes, two of which are radioactive (113 Cd, 116 Cd): 106 Cd, 108 Cd, 110 Cd, 111 Cd, 112 Cd and 114 Cd. Their mass numbers are 106, 108, 110, 111, 112, 113, 114 and 116, respectively. The nucleus of the cadmium isotope 106 Cd contains forty-eight protons and fifty-eight neutrons, and the rest of the isotopes differ from it only in the number of neutrons.

Cadmium ions

At the external energy level of the cadmium atom, there are two electrons, which are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2.

As a result of chemical interaction, cadmium donates its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Cd 0 -2e → Cd 2+.

Cadmium molecule and atom

In a free state, cadmium exists in the form of monoatomic Cd molecules. Here are some properties that characterize the atom and molecule of cadmium:

Cadmium alloys

Cadmium is included as a component in some alloys. For example, copper alloys containing about 1% cadmium (cadmium bronze) are used for the manufacture of telegraph, telephone, trolleybus wires, since these alloys have greater strength and wear resistance than copper. A number of low-melting alloys, such as those used in automatic fire extinguishers, contain cadmium.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2