Lead is one of the rare native metals that has a white-silver color. It is soft, fusible, plastic.
This metal was already known in ancient times. In this article, we will talk about the use, production, physical and chemical properties of plumbum Pb - a chemical element of the periodic table.
What is lead
This is an element in the chemical table at atomic number 82, aka Pb (Plumbum).
In its classic form, it usually has a silver color. Specific gravity - 11.35 g / cm 3.
The history of the discovery of the chemical element Pb
In the Middle East, lead has been known since the 3rd millennium BC, where it was involved in the creation of bricks, statues and various household items. He was associated with Saturn.
Archaeological excavations, which were carried out on the territory of the Old Kingdom of Egypt, helped to find lead products. Similar discoveries were made in the territory of the former Mesopotamia and Armenia.
It was used not only as an independent metal for the product, but also for the purification of silver and gold. Then a new task was found for the metal - they were sheathed on ship hulls and used for medical purposes.
At the end of the 17th century, crystal glass appeared due to the addition of lead to the glass. After that, they began to make bullets from it.
Lead characterization
If you're wondering what color lead is, the answer is plumbum has a bluish-gray tint. It is dense and heavy. Fairly easy to obtain.
Like any of the existing metals, lead is distinguished by its physical and chemical characteristics, which distinguish it from other metals.
Physical properties
The metal is not distinguished by high hardness. It is a rather soft metal, easily cut with a blade. It melts at a low melting point (327 degrees).
The crystallization temperature is 327 degrees, and the boiling point is 2022 K. Plumbum is subject to fairly rapid oxidation in the open air.
Good to know: An unpleasant criterion for lead is its toxicity: in a chronic course, it accumulates in internal organs and bone tissue, which causes disturbances in the body of living beings.
The thermal conductivity is half that of iron.
Molar mass 207.2 a. e.m. ± 0.1 a.u. eat.
The formula of simple oxides is lead oxide (II) PbO and lead oxide (IV) PbO2 and mixed Pb3O4 (red lead).
Chemical properties
It is an inactive metal, standing in front of hydrogen in the electrochemical series, which makes it easily displaced by other metals from solutions of its salts. +2 oxidation state.
Considerably soluble in citric, acetic and tartaric acids. Colorless toxic liquids are derivatives of lead. Its fumes are poisonous.
Some schoolchildren and students ask - is lead magnetized or not? No, there are no such qualities.
In addition to toxicity, I want to know if lead is radioactive or not? Artificial metal isotopes are radioactive.
Basic lead compounds
The halides are formed by reacting with fluorine, chlorine, bromine, iodine, and astatine. Chalcogenides - with oxygen, sulfur, selenium, tellurium, and polonium. Pnictides - with nitrogen and phosphorus.
Areas of use
The element has been widely used:
- In the electrical system, due to its resistance to corrosion, it is used to protect cables, superconductors, lead batteries are used.
- In the military industry, they make bullets and shells, explosives and detonators.
- In medicine, it is a protector against radiation (example: X-ray examination).
- In production - lead is part of cement, used for protective barriers of ceramics and glass.
People who are afraid of lead poisoning ask - where can you find lead? At home, it can be found in batteries, in cables.
Lead production
About half of the metal is produced from ores. The annual production is 5 million tons. Recycling is extremely beneficial in terms of savings.
Lead methods are:
- pyrometallurgical;
- hydrometallurgical.
In the pyrometallurgical method, the existing components are melted down, and in the second, decomposition of existing concentrates is observed.
The largest volumes of lead ore mining can be noted in such countries as:
- China;
- Mexico;
- Australia;
- Peru.
Lead mining in Russia
The seventh place in the production of this metal is occupied by Russia. The share of the Russian Federation in the reserves of this metal is slightly more than 2% due to its low concentration in local deposits. Moreover, lead is exported.
It was calculated that there are about 70 lead deposits in Russia, producing 93% of this metal in such regions as: Krasnoyarsk Territory, Republic of Buryatia, Chita Region, Altai Territory and Primorsky Territory.
This can be expressed as a percentage:
- Siberia - approximately 75%;
- Ural - about 15%;
- Far East - a little less than 10%.
Being in nature
Usually, the metal is mixed with some other metal, such as tin, and does not occur in its pure form.
Lead is a decay stage of uranium, so it can be found in uranium ores. Lead is obtained from raw materials such as galena.
Conclusion
Lead is a metal that has been known to people for thousands of years. Such a science as chemistry now helps to understand its properties in order to use it correctly and economically. Its deposits are located in many parts of the Earth.
In the world market, its price is quite stable. Due to the uniqueness of its physical and chemical properties, Pb is used in many areas and industries, and is subject to import and export.
(first electron)
(according to Pauling)
Pb←Pb 4+ 0.80 V
| Pb | 82 |
| 207,2 | |
| 4f 14 5d 10 6s 2 6p 2 | |
| Lead | |
Lead- an element of the main subgroup of the fourth group, the sixth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 82. It is designated by the symbol Pb (lat. Plumbum). The simple substance lead (CAS number: 7439-92-1) is a malleable, relatively low-melting gray metal.
The origin of the word "lead" is unclear. In most Slavic languages (Bulgarian, Serbo-Croatian, Czech, Polish) lead is called tin. A word with the same meaning, but similar in pronunciation to "lead", is found only in the languages of the Baltic group: švinas (Lithuanian), svins (Latvian).
The Latin plumbum (also of unclear origin) gave the English word plumber - a plumber (once pipes were minted with soft lead), and the name of the Venetian prison with a lead roof - Piombe, from which, according to some sources, Casanova managed to escape. Known since ancient times. Products from this metal (coins, medallions) were used in Ancient Egypt, lead water pipes - in Ancient Rome. An indication of lead as a certain metal is found in the Old Testament. Lead smelting was the first metallurgical process known to man. Prior to 1990, a large amount of lead was used (along with antimony and tin) for casting typographic fonts, as well as in the form of tetraethyl lead - to increase the octane number of motor fuel.
Finding lead in nature
Getting lead
Countries - the largest producers of lead (including secondary lead) for 2004 (according to ILZSG), in thousand tons:
| EU | 2200 |
| USA | 1498 |
| China | 1256 |
| Korea | 219 |
Physical properties of lead
Lead has a rather low thermal conductivity, it is 35.1 W/(m·K) at 0°C. The metal is soft and easy to cut with a knife. On the surface, it is usually covered with a more or less thick film of oxides; when cut, a shiny surface opens, which fades over time in air.
Density - 11.3415 g / cm³ (at 20 ° C)
Melting point - 327.4 ° C
Boiling point - 1740 ° C
Chemical properties of lead
Electronic formula: KLMN5s 2 5p 6 5d 10 6s 2 6p 2, according to which it has oxidation states +2 and +4. Lead is not very reactive chemically. On a metal section of lead, a metallic sheen is visible, gradually disappearing due to the formation of a thin PbO film.
With oxygen, it forms a number of compounds Pb2O, PbO, PbO2, Pb2O3, Pb3O4. Without oxygen, water at room temperature does not react with lead, but at high temperatures lead oxide and hydrogen are produced by the interaction of lead and hot water vapor.
PbO and PbO2 oxides correspond to the amphoteric hydroxides Pb(OH)2 and Pb(OH)4.
The reaction of Mg2Pb and dilute HCl yields a small amount of PbH4. PbH4 is an odorless gaseous substance that decomposes very easily into lead and hydrogen. At high temperatures, halogens form compounds of the form PbX2 with lead (X is the corresponding halogen). All these compounds are slightly soluble in water. Halides of the PbX4 type can also be obtained. Lead does not directly react with nitrogen. Lead azide Pb (N3) 2 is obtained indirectly: by the interaction of solutions of Pb (II) salts and NaN3 salts. Lead sulfides can be obtained by heating sulfur with lead, PbS sulfide is formed. Sulfide is also obtained by passing hydrogen sulfide into solutions of Pb (II) salts. In the series of voltages, Pb is to the left of hydrogen, but lead does not displace hydrogen from dilute HCl and H2SO4, due to the overvoltage of H2 on Pb, and films of sparingly soluble chloride PbCl2 and sulfate PbSO4 are formed on the metal surface, protecting the metal from further action of acids. Concentrated acids such as H2SO4 and HCl, when heated, act on Pb and form with it soluble complex compounds of the composition Pb(HSO4)2 and H2[PbCl4]. Nitric, as well as some organic acids (for example, citric) dissolve lead to form Pb(II) salts. According to their solubility in water, lead salts are divided into insoluble (for example, sulfate, carbonate, chromate, phosphate, molybdate and sulfide), slightly soluble (like chloride and fluoride) and soluble (for example, lead acetate, nitrate and chlorate). Pb (IV) salts can be obtained by electrolysis of solutions of Pb (II) salts strongly acidified with sulfuric acid. Salts of Pb (IV) add negative ions to form complex anions, for example, plumbates (PbO3) 2- and (PbO4) 4-, chloroplumbates (PbCl6) 2-, hydroxoplumbates [Pb (OH) 6] 2- and others. Concentrated solutions of caustic alkalis, when heated, react with Pb with the release of hydrogen and hydroxoplumbites of the X2[Pb(OH)4] type. Eion (Me => Me ++ e) \u003d 7.42 eV.
Basic lead compounds
lead oxides
Lead oxides are predominantly basic or amphoteric in nature. Many of them are painted in red, yellow, black, brown colors. In the photo at the beginning of the article, on the surface of the lead casting, tint colors are visible in its center - this is a thin film of lead oxides formed due to the oxidation of hot metal in air.
Lead halides
Lead chalcogenides
Lead chalcogenides - lead sulfide, lead selenide and lead telluride - are black crystals, which are narrow-gap semiconductors.
lead salts
Lead sulfate
lead nitrate
lead acetate- lead sugar, refers to very toxic substances. Lead acetate, or lead sugar, Pb (CH 3 COO) 2 3H 2 O exists in the form of colorless crystals or a white powder, slowly weathering with the loss of water of hydration. The compound is highly soluble in water. It has an astringent effect, but since it contains poisonous lead ions, it is used externally in veterinary medicine. Acetate is also used in analytical chemistry, dyeing, cotton-printing, as a filler for silk, and for the production of other lead compounds. Basic lead acetate Pb (CH 3 COO) 2 Pb (OH) 2 - less water-soluble white powder - is used to decolorize organic solutions and purify sugar solutions before analysis.
Lead Application
Lead in the national economy
lead nitrate used for the production of powerful mixed explosives. Lead azide is used as the most widely used detonator (initiating explosive). Lead perchlorate is used to prepare a heavy liquid (density 2.6 g/cm³) used in flotation beneficiation of ores, it is sometimes used in powerful mixed explosives as an oxidizing agent. Lead fluoride alone, as well as together with bismuth, copper, silver fluoride, is used as a cathode material in chemical current sources. Lead bismuth, lead sulfide PbS, lead iodide are used as cathode material in lithium batteries. Lead chloride PbCl2 as a cathode material in backup current sources. Lead telluride PbTe is widely used as a thermoelectric material (thermo-emf with 350 μV/K), the most widely used material in the production of thermoelectric generators and thermoelectric refrigerators. Lead dioxide PbO2 is widely used not only in a lead battery, but also many backup chemical current sources are produced on its basis, for example, a lead-chlorine element, a lead-fluorine element, etc.
White lead, basic carbonate Pb (OH) 2.PbCO3, dense white powder, - obtained from lead in air under the action of carbon dioxide and acetic acid. The use of white lead as a coloring pigment is now not as common as it used to be, due to their decomposition by the action of hydrogen sulfide H2S. Lead white is also used for the production of putty, in the technology of cement and lead-carbonate paper.
Lead arsenate and arsenite are used in the technology of insecticides for the destruction of agricultural pests (gypsy moth and cotton weevil). Lead borate Pb(BO2)2 H2O, an insoluble white powder, is used to dry paintings and varnishes, and together with other metals, as coatings on glass and porcelain. Lead chloride PbCl2, white crystalline powder, soluble in hot water, solutions of other chlorides and especially ammonium chloride NH4Cl. It is used for the preparation of ointments in the treatment of tumors.
Lead chromate PbCrO4, known as chrome yellow, is an important pigment for the preparation of paints, for dyeing porcelain and textiles. In industry, chromate is mainly used in the production of yellow pigments. Lead nitrate Pb(NO3)2 is a white crystalline substance, highly soluble in water. It is a binder of limited use. In industry, it is used in matchmaking, textile dyeing and stuffing, antler dyeing, and engraving. Lead sulfate Pb(SO4)2, a water-insoluble white powder, is used as a pigment in batteries, lithography, and printed fabric technology.
Lead sulfide PbS, a black, water-insoluble powder, is used in pottery firing and to detect lead ions.
Since lead is a good absorber of γ-radiation, it is used for radiation shielding in X-ray machines and in nuclear reactors. In addition, lead is considered as a coolant in the projects of advanced fast neutron nuclear reactors.
Lead alloys are widely used. Pewter (tin-lead alloy), containing 85-90% Sn and 15-10% Pb, is moldable, inexpensive and used in the manufacture of household utensils. Solder containing 67% Pb and 33% Sn is used in electrical engineering. Alloys of lead with antimony are used in the production of bullets and typographic type, and alloys of lead, antimony and tin are used for figure casting and bearings. Lead-antimony alloys are commonly used for cable jackets and electric battery plates. Lead compounds are used in the manufacture of dyes, paints, insecticides, glass products, and as additives to gasoline in the form of tetraethyl lead (C2H5) 4Pb (moderately volatile liquid, vapors in small concentrations have a sweetish fruity odor, in large concentrations, an unpleasant odor; Тm = 130 °C, Тbp = 80°С/13 mmHg; density 1.650 g/cm³; nD2v = 1.5198; insoluble in water, miscible with organic solvents; highly toxic, easily penetrates through the skin; MPC = 0.005 mg/m³ LD50 = 12.7 mg/kg (rats, oral)) to increase the octane number.
Lead in medicine
Economic indicators
Prices for lead bullion (grade C1) in 2006 averaged $1.3-1.5/kg.
Countries, the largest consumers of lead in 2004, in thousand tons (according to ILZSG):
| China | 1770 |
| EU | 1553 |
| USA | 1273 |
| Korea | 286 |
Physiological action
Lead and its compounds are toxic. Once in the body, lead accumulates in the bones, causing their destruction. MPC in the atmospheric air of lead compounds is 0.003 mg/m³, in water 0.03 mg/l, in soil 20.0 mg/kg. The release of lead into the World Ocean is 430-650 thousand tons/year.
Lead
LEAD-nca; m.
1. Chemical element (Pb), heavy soft malleable bluish-gray metal (used in the manufacture of batteries, protective shells from harmful radiation, in printing, etc.). Lead mining. Alloy of lead with antimony. Melt with.
2. About the bullet(s). The enemy was met with lead.
◊ Lead in the soul (in the heart, etc.) of someone. About a difficult, oppressive state. Lie like lead on the soul (on the heart, etc.). Induce a severe, oppressive state. The head (arms, legs, etc.) is (as if, exactly) filled with lead (poured). About a feeling of heaviness in the head, arms, legs, etc.
lead(lat. Plumbum), a chemical element of group IV of the periodic system. A bluish-gray metal, heavy, soft, malleable; density 11.34 g / cm 3, t pl 327.5°C. In air, it is covered with an oxide film resistant to chemical attack. Used for the manufacture of plates for batteries (about 30% of smelted lead), sheaths of electrical cables, protection against gamma radiation (walls of lead bricks), as a component of printing and anti-friction alloys, semiconductor materials.
LEADLEAD (lat. plumbum), Pb (read "plumbum"), a chemical element with atomic number 82, atomic mass 207.2. Natural lead consists of five stable isotopes: 202Pb (traces), 204Pb (1.48%), 206Pb (23.6%), 207Pb (22.6%) and 208Pb (52.3%). The last three isotopes are the end products of the radioactive decay of Ac, U, and Th. In nature, radioactive isotopes are formed: 209 Pb, 210 Pb (the historical name is radium D, RaD, T 1/2 = 22 years), 211 Pb (actinium B, AsV, T 1/2 = 36.1 min), 212 Pb ( thorium B, ThB, T 1/2 = 10.6 hours), 214 Pb (radium B, RaB, T 1/2 = 26.8 min).
The configuration of the outer electron layer is 6s 2 p 2 . Oxidation states +2, less often +4 (valency II, IV). It is located in the IVA group, in the 6th period of the Periodic Table of the Elements. The radius of the atom is 0.175 nm, the radius of the Pb 2+ ion is 0.112 nm (coordination number 4) and 0.133 (6), the Pb 4+ ion is 0.133 nm (8). Sequential ionization energies 7.417, 15.032, 31.98, 42.32 and 68.8 eV. The electron work function is 4.05 eV. Electronegativity according to Pauling (cm. PAULING Linus) 1,55.
Lead was known to the inhabitants of Mesopotamia and Ancient Egypt for 7 thousand years BC, lead and its compounds were used in Ancient Greece and Ancient Rome. From lead ores on the island of Rhodes three thousand years ago lead white and red lead were obtained. The pipes of the ancient Roman plumbing were made from lead metal.
The content in the earth's crust is 1.6 10 -3% by weight. Native lead is rare. It is part of 80 different minerals. The most important of them is galena (cm. GALENA) PbS, cerussite (cm. CERUSSIT) PbCO 3 , anglesite (cm. ANGLESITE) PbSO 4 and crocoite (cm. CROCOITE) PbCrO 4 . Always found in uranium ores (cm. Uranium (chemical element)) and thorium (cm. THORIUM).
Receipt
The main source of lead is polymetallic sulfide ores. At the first stage, the ore is enriched. The resulting concentrate is subjected to oxidative roasting:
2PbS + 3O 2 = 2PbO + 2SO 2
During firing, fluxes are added (CaCO 3, Fe 2 O 3, SiO 2). They form a liquid phase that cements the mixture. The resulting agglomerate contains 35-45% Pb. Further, lead(II) and copper oxide contained in the agglomerate are reduced with coke:
PbO + C = Pb + CO and PbO + CO = Pb + CO 2
Black lead is obtained by reacting the original sulfide ore with oxygen (autogenous method). The process takes place in two stages:
2PbS + 3O 2 \u003d 2PbO + 2SO 2,
PbS + 2PbO = 3Pb + SO 2
For the subsequent purification of crude lead from Cu impurities (cm. COPPER), Sb (cm. ANTIMONY), Sn (cm. TIN), Al (cm. ALUMINUM), Bi (cm. BISMUTH), Au (cm. GOLD (chemical element)), and Ag (cm. SILVER) it is purified by pyrometallurgical method or by electrolysis.
Physical and chemical properties
Lead is a bluish-gray metal with a cubic face-centered lattice, a = 0.49389 nm. Density 11.3415 kg/dm3, melting point 327.50°C, boiling point 1715°C. Lead is soft, easily rolled into the thinnest sheets, lead foil. It absorbs x-rays and beta rays well. Chemically, lead is fairly inert. In humid air, the surface of lead tarnishes, first becoming covered with an oxide film, which gradually turns into the basic carbonate 2PbCO 3 ·Pb(OH) 2 .
With oxygen, lead forms oxides: PbO, PbO 2, Pb 3 O 4, Pb 2 O 3, Pb 12 O 17, Pb 12 O 19, of which the first three exist in the low-temperature a-form and high-temperature b-form. If lead hydroxide Pb (OH) 2 is boiled in a large amount of alkali, red a-PbO is formed. With a lack of alkali, yellow b-PbO is formed (see lead oxides (cm. LEAD OXIDES)). If a suspension of a-PbO is boiled for a long time, it turns into b-PbO. The transition of a-PbO to b-PbO at room temperature proceeds very slowly. b-PbO is obtained by thermal decomposition of PbCO 3 and Pb (NO 3) 2:
PbCO 3 \u003d PbO + CO 2; 2Pb (NO 3) 2 \u003d 2PbO + 4NO 2 + O 2
Both forms are found in nature: a-PbO - the mineral litharge, b-PbO - the mineral massicot. If a fine a-PbO powder is calcined at 500°C in a stream of air, then a high-temperature red modification of a-Pb 3 O 4 is formed. Below a temperature of -90°C a-Pb 3 O 4 goes into the b-form of this oxide. By electrochemical oxidation of lead (II) salts, the a-form of lead dioxide PbO 2 can be obtained. By carefully heating a-PbO 2 in air to 200-570°C, Pb 12 O 19 (decomposition temperature 200°C), Pb 12 O 17 (350°C), Pb 3 O 4 (380°C) and PbO (570 °C). PbO oxide has amphoteric (cm. AMPHOTERICITY) properties. Reacts with acids:
PbO + 2CH 3 COOH \u003d Pb (CH 3 COO) 2 + H 2 O
and with alkali solutions:
PbO + KOH \u003d K 2 PbO 2 + H 2 O
Potassium plumbate K 2 PbO 2 is also formed by the interaction of lead with an alkali solution:
Pb + 2KOH \u003d K 2 PbO 2 + H 2
In PbO 2, acidic properties predominate, it is a strong oxidizing agent. Oxide Pb 3 O 4 can be considered as a lead salt of ortholead acid Pb 2 . At room temperature, lead does not react with sulfuric and hydrochloric acids, since poorly soluble lead sulfate PbSO 4 and lead chloride PbCl 2 are formed on its surface. But with organic acids (acetic (cm. ACETIC ACID) and formic (cm. FORMIC ACID)), and also reacts with dilute nitric acid to form lead(II) salts:
3Pb + 8HNO 3 \u003d 3Pb (NO 3) 2 + 2NO + 4H 2 O
When lead reacts with acetic acid, with a purge of oxygen, lead acetate Pb(CH 3 COO) 2 is formed, "lead sugar", which has a sweet taste.
Up to 45% of lead is used to make acid battery plates. 20% - for the manufacture of wires, cables and coatings for them. Lead screens are used to protect against radioactive and X-ray radiation. Containers for storing radioactive substances are made from lead and its alloys. lead alloys With Sb (cm. ANTIMONY),
sn (cm. TIN) and Cu (cm. COPPER) used for the manufacture of typographic fonts, from lead alloys with Sb and As (cm. ARSENIC) they make bullet cores, shrapnel, shot. 5-20% of lead is used to produce tetraethyl lead (TES) Pb(C 2 H 5) 4 , which is added to gasoline to increase the octane number. Lead is used in the production of pigments, for the construction of earthquake-resistant foundations.
Lead and its compounds are toxic. Once in the body, lead accumulates in the bones, causing their destruction. MPC in the atmospheric air of lead compounds is 0.003 mg / m 3, in water 0.03 mg / l, soil 20.0 mg / kg. Release of lead into the World Ocean is 430-650 thousand tons/year.
encyclopedic Dictionary. 2009 .
Synonyms:See what "lead" is in other dictionaries:
LEAD- ordinary (Plumbum), symbol. Pb, mixture of isotopes, atomic c. 207.22 (at. w. uranium lead 206.05, thorium lead 207.9). In addition to these isotopes, there is also lead with at. V. 207. The ratio of isotopes in ordinary lead206:: 207: 208 = 100: 75:175. ... ... Big Medical Encyclopedia
Husband. crusher, metal, one of the softest and most weighty, bluer than tin; in old times they called it tin, hence the saying: the word tin, i.e. weightily. In Vasiliev evening pour tin, lead, wax. Rifle bullets are lead. Lead ore is always ... ... Dahl's Explanatory Dictionary
- (symbol Pb), a metal element of group IV of the periodic table. Its main ore is GALENITE (lead sulfide), lead is mined from it by roasting. Exposure to lead found in paints, pipes, gasoline, etc. can lead to ... ... Scientific and technical encyclopedic dictionary
- (Plumbum), Pb, chemical element of group IV of the periodic system, atomic number 82, atomic mass 207.2; soft, ductile bluish-gray metal, mp 327.5shC, volatile. Lead is used to make battery electrodes, wires, cables, bullets, pipes and ... ... Modern Encyclopedia
LEAD, lead, pl. no, husband. 1. Soft, very heavy bluish gray metal. Lead seal. Molten lead. 2. trans. Bullet; collected bullets (poet.) "Destructive lead will whistle around me." Pushkin. "With lead in my chest, I lay motionless ... Explanatory Dictionary of Ushakov
- (Pb) chem. element IV gr. periodic system, serial number 82, at. V. 207.19. S. is characterized by positive valencies 4 and 2, the most typical are compounds in which it is divalent. Quadrivalent S. in an acidic environment is ... ... Geological Encyclopedia
Lead(lat. plumbum), pb, a chemical element of group iv of Mendeleev's periodic system; atomic number 82, atomic mass 207.2. S. - a heavy metal of a bluish-gray color, very plastic, soft (cut with a knife, scratched with a fingernail). Natural S. consists of 5 stable isotopes with mass numbers 202 (traces), 204 (1.5%), 206 (23.6%), 207 (22.6%), 208 (52.3%). The last three isotopes are the end products of radioactive transformations 238 u, 235 u and 232 th . Numerous radioactive isotopes C are formed in nuclear reactions. Historical background. S. was known for 6-7 thousand years BC. e. the peoples of Mesopotamia, Egypt and other countries of the ancient world. He served for the manufacture of statues, household items, tablets for writing. The Romans used lead pipes for plumbing. Alchemists called S. Saturn and designated it with the sign of this planet . S. compounds - "lead ash" pbo, lead white 2pbco 3 pb (oh) 2 were used in ancient Greece and Rome as components of medicines and paints. When firearms were invented, S. began to be used as a material for bullets. The poisonousness of S. was noted as early as the 1st century. n. e. Greek physician Dioscorides and Pliny the Elder, Distribution in nature. The content of S. in the earth's crust (clarke) 1.6 10 -3% by weight. The formation in the earth's crust of about 80 minerals containing S. (the main of them is galena pbs) is associated mainly with the formation hydrothermal deposits . Numerous (about 90) secondary minerals are formed in the oxidation zones of polymetallic ores: sulfates (anglesite pbso 4), carbonates (cerussite pbco 3), phosphates [pyromorphite pb 5 (po 4) 3 cl]. In the biosphere, S. is mainly dispersed, it is small in living matter (5 × 10 -5%), sea water (3 × 10 -9%). From natural waters, sulfur is partly sorbed by clays and precipitated by hydrogen sulfide; therefore, it accumulates in marine silts contaminated with hydrogen sulfide and in the black clays and shales formed from them. Physical and chemical properties. S. crystallizes in a face-centered cubic lattice ( a = 4.9389 å), has no allotropic modifications. Atomic radius 1.75 å, ionic radii: pb 2+ 1.26 å, pb 4+ 0.76 å: density 11.34 g/cm 3(20°C); t nl 327.4 °С; t kip 1725 °С; specific heat capacity at 20°C 0.128 kJ/(kg· TO) ; thermal conductivity 33.5 Tue/(m· TO) ; temperature coefficient of linear expansion 29.1 10 -6 at room temperature; Brinell hardness 25-40 MN/m 2 (2,5-4 kgf/mm 2) ; tensile strength 12-13 MN / m 2, at compression about 50 MN/m 2 ; relative elongation at break 50-70%. hardening does not increase the mechanical properties of S., since the temperature of its recrystallization lies below room temperature (about -35 ° C at a degree of deformation of 40% and above). S. is diamagnetic, its magnetic susceptibility is 0.12 10 -6. At 7.18 K it becomes a superconductor.
The configuration of the outer electron shells of the atom pb 6s 2 6r 2, whereby it exhibits oxidation states +2 and +4. The page is rather a little active chemically. The metallic luster of a fresh section of S. gradually disappears in air due to the formation of a very thin film of pbo, which protects against further oxidation. With oxygen, it forms a series of oxides pb 2 o, pbo, pbo 2, pb 3 o 4 and pb 2 o 3 .
In the absence of o 2, water at room temperature does not act on S., but it decomposes hot water vapor with the formation of S. oxide and hydrogen. The hydroxides pb (oh) 2 and pb (oh) 4 corresponding to the oxides pbo and pbo 2 are amphoteric in nature.
S.'s connection with hydrogen pbh 4 is obtained in small quantities by the action of dilute hydrochloric acid on mg 2 pb. pbh 4 is a colorless gas that decomposes very easily into pb and h 2 . When heated, carbon combines with halogens to form pbx 2 halides (x is a halogen). All of them are slightly soluble in water. Pbx 4 halides were also obtained: pbf 4 tetrafluoride - colorless crystals and pbcl 4 tetrachloride - yellow oily liquid. Both compounds are easily decomposed, releasing f 2 or cl 2 ; hydrolyzed by water. S. does not react with nitrogen . lead azide pb(n 3) 2 obtained by the interaction of solutions of sodium azide nan 3 and salts pb (ii); colorless needle-shaped crystals, sparingly soluble in water; on impact or heating decomposes into pb and n 2 with an explosion. Sulfur acts on sulfur when heated to form pbs sulfide, a black amorphous powder. Sulfide can also be obtained by passing hydrogen sulfide into solutions of salts pb (ii); found in nature in the form of lead luster - galena.
In the series of voltages, pb is higher than hydrogen (normal electrode potentials, respectively, are - 0.126 V for pb u pb 2+ + 2e and + 0.65 V for pb u pb 4+ + 4e). However, S. does not displace hydrogen from dilute hydrochloric and sulfuric acids, due to surge h 2 on pb, as well as the formation of protective films of sparingly soluble chloride pbcl 2 and sulfate pbso 4 on the metal surface. Concentrated h 2 so 4 and hcl, when heated, act on pb, and soluble complex compounds of the composition pb (hso 4) 2 and h 2 are obtained. Nitric, acetic, and some organic acids (for example, citric) dissolve C. to form pb(ii) salts. According to their solubility in water, salts are divided into soluble (lead acetate, nitrate and chlorate), slightly soluble (chloride and fluoride) and insoluble (sulfate, carbonate, chromate, phosphate, molybdate and sulfide). Salts pb (iv) can be obtained by electrolysis of strongly acidified h 2 so 4 solutions of salts pb (ii); the most important of the salts of pb (iv) are sulfate pb (so 4) 2 and acetate pb (c 2 h 3 o 2) 4. Salts pb (iv) tend to add excess negative ions to form complex anions, for example plumbates (pbo 3) 2- and (pbo 4) 4-, chloroplumbates (pbcl 6) 2-, hydroxoplumbates 2-, etc. Concentrated solutions of caustic alkalis at when heated, they react with pb with the release of hydrogen and hydroxoplumbites of the x 2 type.
Receipt. Metallic silver is obtained by oxidative roasting of pbs, followed by reduction of pbo to raw pb (“werkble”) and refining (purification) of the latter. Oxidative roasting of the concentrate is carried out in continuous sintering belt machines . When firing pbs, the reaction prevails: 2pbs + 3o 2 = 2pbo + 2so 2. In addition, a little sulfate pbso 4 is also obtained, which is converted into silicate pbsio 3, for which quartz sand is added to the mixture. At the same time, sulfides of other metals (cu, zn, fe), which are present as impurities, are also oxidized. As a result of firing, instead of a powdery mixture of sulfides, an agglomerate is obtained - a porous sintered continuous mass, consisting mainly of oxides pbo, cuo, zno, fe 2 o 3. Pieces of agglomerate are mixed with coke and limestone and this mixture is loaded into water jacket oven, into which air is supplied under pressure from below through pipes (“tuyeres”). Coke and carbon monoxide reduce pbo to pb already at low temperatures (up to 500 °C). At higher temperatures, the following reactions take place:
caco 3 = cao + co 2
2pbsio 3 + 2cao + C = 2pb + 2casio 3 + co 2 .
Oxides zn and fe partially transform into znsio 3 and fesio 3 , which together with casio 3 form a slag that floats to the surface. S.'s oxides are reduced to metal. Raw S. contains 92-98% pb, the rest - impurities cu, ag (sometimes au), zn, sn, as, sb, bi, fe. Impurities cu and fe are removed seigerization. To remove sn, as, sb, air is blown through the molten metal. Allocation of ag (and au) is carried out by adding zn, which forms a "zinc foam" consisting of compounds zn with ag (and au), lighter than pb, and melting at 600-700 ° C. Excess zn is removed from molten pb by passing air, water vapor, or chlorine. To remove bi, ca or mg are added to liquid pb, giving refractory compounds ca 3 bi 2 and mg 3 bi 2 . C. refined by these methods contains 99.8-99.9% pb. Further purification is carried out by electrolysis, resulting in a purity of at least 99.99%. Application. S. is widely used in the production of lead batteries, used for the manufacture of factory equipment, resistant to aggressive gases and liquids. C. strongly absorbs g-rays and x-rays, due to which it is used as a material for protection against their action (containers for storing radioactive substances, equipment for x-ray rooms, etc.). Large quantities of S. are used to make sheaths of electrical cables, which protect them from corrosion and mechanical damage. Many are made on the basis of S. lead alloys. C. pbo oxide is introduced into crystal and optical glass to obtain materials with a high refractive index. Minium, chromate (yellow crown), and basic carbonate S. (lead white) are pigments that are used to a limited extent. S. chromate is an oxidizing agent used in analytical chemistry. Azide and styphnate (trinitroresorcinate) are initiating explosives. Tetraethyl lead - antiknock. S.'s acetate serves as an indicator for the detection of h 2 s. 204 pb (stable) and 212 pb (radioactive) are used as isotope tracers.
S. A. Pogodin.
S. in the body. Plants absorb S. from soil, water, and atmospheric precipitation. S. enters the human body with food (about 0.22 mg) , water (0.1 mg) , dust (0.08 mg) . Safe daily level of intake of S. for a person 0.2-2 mg. Excreted mainly with feces (0.22-0.32 mg) , less with urine (0.03-0.05 mg) . The human body contains on average about 2 mg C. (in some cases - up to 200 mg) . Inhabitants of industrialized countries, the content of S. in the body is higher than that of inhabitants of agrarian countries, and that of city dwellers is higher than that of rural dwellers. The main depot of S. is the skeleton (90% of the total S. of the body): 0.2-1.9 accumulates in the liver µg/g; in the blood - 0.15-0.40 mcg/ml; in hair - 24 mcg/g in milk -0.005-0.15 mcg/ml; is also found in the pancreas, kidneys, brain, and other organs. S.'s concentration and distribution in an organism of animals are close to the indicators established for the person. With an increase in the level of S. in the environment, its deposition in the bones, hair, and liver increases. Biological functions of S. are not established.
Yu. I. Raetskaya.
poisoning C. and its compounds are possible in the mining of ores, the smelting of lead, in the production of lead paints, in printing, pottery, and cable production, in the production and use of tetraethyl lead, and others. dishes covered with glaze containing red lead or litharge. S. and its inorganic compounds in the form of aerosols penetrate the body mainly through the respiratory tract, to a lesser extent through the gastrointestinal tract and skin. S.'s blood circulates in the form of highly dispersed colloids - phosphate and albuminate. S. is allocated mainly through the intestines and kidneys. Violation of porphyrin, protein, carbohydrate, and phosphate metabolism, deficiency of vitamins C and b 1 , functional and organic changes in the central and autonomic nervous system, and S.'s toxic effect on the bone marrow play a role in the development of intoxication. Poisoning can be latent (the so-called carriage), occur in mild, moderate and severe forms.
The most common signs of poisoning with S. : a border (a strip of lilac-slate color) along the edge of the gums, an earthy-pale color of the skin; reticulocytosis and other blood changes, elevated levels of porphyrins in the urine, the presence of S. in the urine in quantities of 0.04-0.08 mg/l and more, etc. Damage to the nervous system is manifested by asthenia, with severe forms - encephalopathy, paralysis (mainly of the extensors of the hand and fingers), polyneuritis. With the so-called. lead colic, there are sharp cramping pains in the abdomen, constipation, lasting from several h up to 2-3 week; often colic is accompanied by nausea, vomiting, rise in blood pressure, body temperature up to 37.5-38 ° C. In chronic intoxication, damage to the liver, cardiovascular system, and endocrine dysfunction (for example, in women - miscarriages, dysmenorrhea, menorrhagia, etc.) are possible. Inhibition of immunobiological reactivity contributes to increased overall morbidity.
Treatment: specific (complexing agents, etc.) and restorative (glucose, vitamins, etc.) agents, physiotherapy, spa treatment (Pyatigorsk, Matsesta, Sernovodsk). Prevention: replacing S. with less toxic substances (for example, zinc and titanium white instead of lead), automation and mechanization of operations in the production of S., effective exhaust ventilation, individual protection of workers, clinical nutrition, periodic fortification, preliminary and periodic medical examinations.
S.'s preparations are used in medical practice (only externally) as astringents and antiseptics. Apply: lead water (for inflammatory diseases of the skin and mucous membranes), simple and complex lead plasters (for purulent-inflammatory diseases of the skin, boils), etc.
L. A. Kasparov.
Lit.: Andreev V. M., Lead, in the book: Brief Chemical Encyclopedia, v. 4, M., 1965; Remi G., Course of inorganic chemistry, trans. from German, vol. 1, M., 1963; Chizhikov D. M., Metallurgy of lead, in the book: A metallurgist's guide to non-ferrous metals, vol. 2, M., 1947; Harmful substances in industry, ed. N. V. Lazareva, 6th ed., part 2, L., 1971; Tarabaeva G. I., The effect of lead on the body and therapeutic and preventive measures, A.-A., 1961; Occupational diseases, 3rd ed., M., 1973,
Lead is a soft, heavy, silvery-gray metal that is lustrous but loses its luster fairly quickly. On a par with and refers to the elements known to mankind since ancient times. Lead was used very widely, and even now its use is extremely diverse. So, today we will find out whether lead is a metal or non-metal, as well as a non-ferrous or ferrous metal, learn about its types, properties, applications and extraction.
Lead is an element of group 14 of the table of D. I. Mendeleev, located in the same group with carbon, silicon and tin. Lead is a typical metal, but inert: it reacts extremely reluctantly even with strong acids.
The molecular weight is 82. This not only indicates the so-called magic number of protons in the nucleus, but also the large weight of the substance. The most interesting qualities of the metal are associated precisely with its large weight.
The concept and features of lead metal are discussed in this video:
Concept and features
Lead is a fairly soft metal at normal temperatures and can easily be scratched or flattened. Such ductility makes it possible to obtain sheets and bars of metal of very small thickness and any shape. Malleability was one of the reasons why lead has been used since antiquity.
Lead water pipes of ancient Rome are well known. Since then, this kind of water supply has been installed more than once and in more than one place, but it did not work for so long. Which, no doubt, saved a considerable number of human lives, since lead, alas, with prolonged contact with water, eventually forms soluble compounds that are toxic.
Toxicity is the very property of the metal, due to which they try to limit its use. Metal vapors and many of its organic and inorganic salts are very dangerous for both the environment and people. Basically, of course, the workers of such enterprises and residents of the zone around the industrial facility are at risk. 57% is emitted together with large volumes of dusty gas, and 37% - with converter gases. There is only one problem with this - the imperfection of purification plants.
However, in other cases, people become victims of lead pollution. Until recently, tetraethyl lead has been the most effective and popular gasoline stabilizer. During the combustion of fuel, it was released into the atmosphere and polluted it.
But lead has another, extremely useful and necessary quality - the ability to absorb radioactive radiation. Moreover, the metal absorbs the hard component even better than the soft one. A lead layer 20 cm thick is capable of protecting against all types of radiation known on Earth and in near space.
Advantages and disadvantages
Lead combines properties that are extremely useful, turning into an irreplaceable element, and frankly dangerous, which make its use a very difficult task.
The advantages from the point of view of the national economy include:
- fusibility and ductility - this allows you to form metal products of any degree of complexity and any subtlety. So, for the production of sound-absorbing membranes, lead plates with a thickness of 0.3–0.4 mm are used;
- lead is able to form an alloy with other metals (including, etc.) that under normal conditions do not alloy with each other, its use as a solder is based on this quality;
- metal absorbs radiation. Today, all elements of protection against radiation - from clothing to the decoration of X-ray rooms and rooms at test sites, are made from lead;
- the metal is resistant to acids, second only to noble gold and silver. So it is actively used for lining acid-resistant equipment. For the same reasons, it is used to produce pipes for acid transmission and for wastewater in hazardous chemical plants;
- the lead battery has not yet lost its importance in electrical engineering, as it allows you to get a high voltage current;
- low cost - lead is 1.5 times cheaper than zinc, 3 times copper, and almost 10 times tin. This explains the very great advantage of using lead, and not other metals.
The disadvantages are:
- toxicity - the use of metal in any type of production is a danger to personnel, and in case of accidents it is an extreme danger to the environment and the population. Lead belongs to substances of the 1st hazard class;
- Lead products should not be disposed of as normal trash. They require disposal and are sometimes very costly. Therefore, the issue of metal recycling is always relevant;
- Lead is a soft metal, so it cannot be used as a structural material. Considering all his other qualities, this should rather be considered a plus.
Properties and characteristics
Lead is a soft, malleable, but heavy and dense metal. The molecular lattice is cubic, face-centered. Its strength is low, but its ductility is excellent. The physical characteristics of the metal are as follows:
- density at normal temperature 11.34 g/cc;
- melting point - 327.46 C;
- boiling point - 1749 C;
- resistance to tensile load - 12–3 MPa;
- resistance to compressive load - 50 MPa;
- Brinell hardness - 3.2–3.8 HB;
- thermal conductivity - 33.5 W / (m K);
- resistivity is 0.22 ohm-sq. Mmm.
Like any metal, it conducts electric current, although, it should be noted, it is much worse than copper - almost 11 times. However, the metal has another interesting property: at a temperature of 7.26 K, it becomes a superconductor and conducts electricity without any resistance. Lead was the first element to exhibit this property.
In air, a piece of metal or a product made of it is rather quickly passivated by an oxide film, which successfully protects the metal from external influences. And the substance itself is not prone to chemical activity, which is why it is used in the manufacture of acid-resistant equipment.
Paints containing lead compounds are almost as resistant to corrosion. Due to toxicity, they are not used indoors, but they are successfully used in painting bridges, for example, frame structures, and so on.
The video below will show you how to make pure lead:
Structure and composition
In the entire temperature range, only one modification of lead is isolated, so both under the influence of temperature and over time, the properties of the metal change quite naturally. No abrupt transitions, when the qualities change dramatically, were noted.
Metal production
Lead is quite common, forms several industrially significant minerals - galena, cerussite, anglesite, so its production is relatively cheap. pyrometallurgical and hydrometallurgical methods. The second method is safer, but it is used much less frequently, since it is more expensive, and the resulting metal still needs to be finished at a high temperature.
Production by the pyrometallurgical method includes the following stages:
- ore mining;
- crushing and enrichment mainly by the flotation method;
- smelting in order to obtain crude lead - reduction, hearth, alkaline, and so on;
- refining, that is, cleaning black lead from impurities and obtaining pure metal.
Despite the same production technology, equipment can be used in a variety of ways. It depends on the metal content in the ore, production volumes, product quality requirements, and so on.
Read about the use and price for 1 kg of lead below.
Application area
The first - the manufacture of water pipes and household items, fortunately, dates back to quite ancient times. Today, metal enters the home only with a protective layer and in the absence of contact with food, water and humans.
- But the use of lead for alloys and as solder began at the dawn of civilization and continues to this day.
- Lead is a metal of strategic importance, especially since bullets have been cast from it. Ammunition for small arms and sporting weapons is still made only from lead. And its compounds are used as explosives.
- 75% of the metal produced in the world is used for the production of lead batteries. The substance continues to be one of the main elements of chemical current sources.
- The corrosion resistance of the metal is exploited in the manufacture of acid-resistant equipment, pipelines, as well as protective sheaths for power cables.
- And, of course, lead is used in the equipment of X-ray rooms: wall, ceiling, floor cladding, protective partitions, protective suits - everything is made with lead. At test sites, including nuclear ones, metal is indispensable.
The cost of metals is determined on several exchanges of world importance. The most famous is the London Metal Exchange. The cost of lead in October 2016 is $2,087.25 per ton.
Lead is a metal very much in demand in modern industry. Some of its qualities - corrosion resistance, the ability to absorb hard radiation - are completely unique and make the metal indispensable despite its high toxicity.
This video will tell you what happens if you pour lead into water:
