Lead discovery story. Lead minerals and types of lead ores

Lead is a metal that has been known since ancient times. Man has been using it since 2-3 thousand BC, and it was first discovered in Mesopotamia. There, small bricks, figurines, and various household items were made from lead. Even then, people obtained bronze using this element, and also made it for writing with sharp objects.

What color is the metal?

It is an element of group IV of period 6 of the periodic table, where it has the serial number 82. What is lead in nature? It is the most commonly found galena and the formula is PbS. Otherwise, galena is called lead luster. The pure element is a soft and malleable metal of a dirty gray color. In air, its cut quickly becomes covered with a small layer of oxide. Oxides reliably protect the metal from further oxidation in both wet and dry environments. If a metal surface coated with oxides is cleaned, it will acquire a shiny tint with a blue tint. This cleaning can be done by pouring the lead in a vacuum and sealing it into a vacuum flask.

Interaction with acids

Sulfuric and hydrochloric acids have a very weak effect on lead, but the metal easily dissolves in nitric acid. All metal chemical compounds that may be soluble are poisonous. It is obtained mainly from ores: first, lead luster is burned until it turns into lead oxide, and then this substance is reduced with coal to pure metal.

General Element Properties

The density of lead is 11.34 g/cm3. This is 1.5 times the density of iron and four times that of lightweight aluminum. It is not without reason that in Russian the word "lead" is a synonym for the word "heavy". The melting of lead occurs at a temperature of 327.5 ° C. The metal becomes volatile already at an ambient temperature of 700 ° C. This information is very important for those who work in the mining of this metal. It is very easy to scratch even with a fingernail, and it is easy to roll into thin sheets. This is a very soft metal.

Interaction with other metals, heating

The specific heat capacity of lead is 140 J/kg. According to its chemical properties, it is a low-active metal. In the voltage series it is located in front of hydrogen. Lead is easily replaced from its salts by other metals. For example, you can conduct an experiment: dip a zinc stick into a solution of acetate of this element. Then it will settle on the zinc stick in the form of fluffy crystals, which chemists call “Saturn wood.” What is the specific heat of lead? What does this mean? This figure is 140 J/kg. This means the following: to heat a kilogram of metal by 1 o C, 140 Joules of heat are required.

Distribution in nature

There is not so much of this metal in the earth's crust - only 0.0016% by mass. However, even this value shows that it is more abundant than mercury, bismuth and gold. Scientists attribute this to the fact that various lead isotopes are decay products of thorium and uranium, so lead levels in the Earth's crust have slowly increased over millions of years. At the moment, many lead ores are known - this is the already mentioned galena, as well as the results of its chemical transformations.

The latter include lead sulfate, cerussite (another name is white mimetite, stoltsite. The ores also contain other metals - cadmium, copper, zinc, silver, bismuth. Where lead ores occur, not only the soil is saturated with this metal, but also water bodies, plants. What is lead in nature? It is always a specific compound. This metal is also found in ores of radioactive metals - uranium and thorium.

Heavy metal in industry

The most commonly used in industry is a compound of lead and tin. Ordinary solder called "tertiary" is widely used for connecting pipelines and electrical wires. This compound contains one part lead and two parts tin. Sheaths for telephone cables and parts of batteries may also contain lead. The melting point of some of its compounds is very low - for example, alloys with cadmium or tin melt at 70 o C. Fire-fighting equipment is made from such compounds. Metal alloys are widely used in shipbuilding. They are usually colored light gray. Ships are often coated with tin and lead alloys to protect against corrosion.

Meaning for people of the past and application

The Romans used this metal to make pipes in pipelines. In ancient times, people associated lead with the planet Saturn, and therefore it was previously called Saturn. In the Middle Ages, due to its heavy weight, the metal was often used for alchemical experiments. He was often credited with the ability to turn into gold. Lead is a metal that was very often confused with tin, which continued until the 17th century. And in ancient Slavic languages ​​it bore this name.

It has reached the modern Czech language, where this heavy metal is called olovo. Some linguistic experts believe that the name Plumbum is associated with a specific Greek area. The Russian origin of the word “lead” is still unclear to scientists. Some linguists associate it with the Lithuanian word "scwinas".

The traditional use of lead in history is in the manufacture of bullets, shotgun pellets, and various other projectiles. It was used because it was cheap and had a low melting point. Previously, when making gun shot, a small amount of arsenic was added to the metal.

Lead was also used in Ancient Egypt. Building blocks, statues of noble people were made from it, and coins were minted. The Egyptians were sure that lead had special energy. They made small plates out of it and used them to protect themselves from ill-wishers. And the ancient Romans didn't just make water pipes. They also produced cosmetics from this metal, without even suspecting that they were signing their own death warrant. After all, when lead entered the body every day, it caused serious illnesses.

What about the modern environment?

There are substances that kill humanity slowly but surely. And this applies not only to the unenlightened ancestors of antiquity. Sources of toxic lead today are cigarette smoke and urban dust from residential buildings. Vapors from paints and varnishes are also dangerous. But the greatest harm comes from car exhaust gases, which contain large quantities of lead.

But not only residents of megacities are at risk, but also those who live in villages. Here the metal can accumulate in soils and then end up in fruits and vegetables. As a result, humans receive more than a third of lead through food. In this case, only powerful antioxidants can serve as an antidote: magnesium, calcium, selenium, vitamins A, C. If you use them regularly, you can reliably neutralize yourself from the harmful effects of the metal.

Harm

Every student knows what lead is. But not all adults are able to answer the question of what is its harm. Its particles enter the body through the respiratory system. Further, it begins to interact with the blood, reacting with various parts of the body. The musculoskeletal system suffers the most from this. Here is 95% of all lead consumed by man.

A high level of its content in the body leads to mental retardation, and in adults it manifests itself in the form of depressive symptoms. Excess is evidenced by absent-mindedness, fatigue. The intestines also suffer - due to lead, spasms can often occur. This heavy metal also negatively affects the reproductive system. It becomes difficult for women to bear a fetus, and men may experience problems with sperm quality. It is also very dangerous for the kidneys. According to some studies, it can cause malignant tumors. However, in amounts not exceeding 1 mg, lead can be beneficial to the body. Scientists have found that this metal can have a bactericidal effect on the organs of vision - however, one should remember what lead is and use it only in doses that do not exceed the permissible ones.

As a conclusion

As already mentioned, in ancient times the planet Saturn was considered the patron of this metal. But Saturn in astrology is an image of loneliness, sadness and hard fate. Is this why lead is not the best companion for humans? Perhaps he should not impose his society, as the ancients intuitively suggested when they called lead Saturn. After all, the harm to the body from this metal can be irreparable.

2.1 General information and history of the discovery of the element lead

Lead (English Lead, French Plomb, German Blei) has been known since the 3rd - 2nd millennium BC. in Mesopotamia, Egypt and other ancient countries, where large bricks (ingots), statues of gods and kings, seals and various household items were made from it. Bronze was made from lead, as well as tablets for writing with a sharp, hard object. At a later time, the Romans began to make water pipes from lead. In ancient times, lead was associated with the planet Saturn and was often called Saturn. In the Middle Ages, due to its heavy weight, lead played a special role in alchemical operations; it was credited with the ability to easily turn into gold. Until the 17th century. Lead was often confused with tin. In ancient Slavic languages ​​it was called tin; this name is preserved in modern Czech (Olovo). The ancient Greek name for lead is probably associated with some locality. Some philologists compare the Greek name with the Latin Plumbum and argue that the latter word was formed from mlumbum. Others point out that both these names come from the Sanskrit bahu-mala (very dirty); in the 17th century distinguished between Plumbum album (white lead, i.e. tin) and Plumbum nigrum (black lead). In alchemical literature, lead had many names, some of which were secret. The Greek name was sometimes translated by alchemists as plumbago - lead ore. The German Blei is usually not derived from Lat. Plumbum, despite the obvious consonance, and from the ancient German blio (bliw) and the related Lithuanian bleivas (light, clear), but this is not very reliable. The name Blei is associated with the English. Lead and Danish Lood.

Lead (Plumbum) Рb is an element of group IV of the 6th period of the periodic system of D. I. Mendeleev, number 82, atomic mass 207.19.

Native lead is rare, the most important mineral is galena (lead luster) PbS. Lead is a soft, malleable and ductile gray metal. In air, it quickly becomes covered with a thin layer of oxide, which protects it from further oxidation. In the electrochemical series of voltages, lead is directly in front of hydrogen. Shows valency 2+, as well as 4+. Quadrivalent lead compounds are much less stable. Dilute hydrochloric and sulfuric acids have almost no effect on lead due to the low solubility of PbCl 2 and PbS0 4. Easily dissolves in nitric acid. Lead, like its hydroxide, dissolves in alkalis, and plumbite ions are formed. All soluble lead compounds are poisonous. Lead reacts with strong sulfuric acid (at a concentration of more than 80%) to form soluble hydrosulfate Pb(HSO 4) 2, and in hot concentrated hydrochloric acid, dissolution is accompanied by the formation of complex chloride H 4 PbCl 6.

In the presence of oxygen, lead also dissolves in a number of organic acids. The action of acetic acid produces readily soluble acetate Pb(CH 2 COO) 2 (the old name is “lead sugar”). Lead is also noticeably soluble in formic, citric and tartaric acids. The solubility of lead in organic acids could previously lead to poisoning if food was cooked in dishes tinned or soldered with lead solder. Soluble lead salts (nitrate and acetate) in water hydrolyze:

Pb(NO 3) 2 + H 2 O Pb(OH)NO 3 + HNO 3

When heated, lead reacts with oxygen, sulfur and halogens. Thus, in a reaction with chlorine, PbCl 4 tetrachloride is formed - a yellow liquid that smokes in air due to hydrolysis, and when heated, decomposes into PbCl 2 and Cl 2. (The halides PbBr 4 and PbI 4 do not exist, since Pb(IV) is a strong oxidizing agent that would oxidize bromide and iodide anions.) Finely ground lead has pyrophoric properties - it flares up in air. With prolonged heating of molten lead, it gradually turns first into yellow oxide PbO (lead litharge), and then (with good air access) into red lead Pb 3 O 4 or 2PbO·PbO 2. This compound can also be considered as the lead salt of ortholead acid Pb 2. With the help of strong oxidizing agents, such as bleach, lead(II) compounds can be oxidized to dioxide:

Pb(CH 3 COO) 2 + Ca(ClO)Cl + H 2 O ® PbO 2 + CaCl 2 + 2CH 3 COOH.

Dioxide is also formed when red lead is treated with nitric acid:

Pb 3 O 4 + 4HNO 3 ® PbO 2 + 2Pb(NO 3) 2 + 2H 2 O.

If you heat brown dioxide strongly, then at a temperature of about 300 ° C it will turn into orange Pb 2 O 3 (PbO PbO 2), at 400 ° C - into red Pb 3 O 4, and above 530 ° C - into yellow PbO ( decomposition is accompanied by the release of oxygen).

Organic lead derivatives are colorless, highly toxic liquids. One of the methods for their synthesis is the action of alkyl halides on a lead-sodium alloy:

4C 2 H 5 Cl + 4PbNa ® (C 2 H 5) 4 Pb + 4NaCl + 3Pb

The action of gaseous HCl can eliminate one alkyl radical after another from tetrasubstituted lead, replacing them with chlorine. R 4 Pb compounds decompose when heated to form a thin film of pure metal. This decomposition of tetramethyl lead was used to determine the lifetime of free radicals.

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From the curse of the Roman Empire to the Cathedral of Christ the Savior This gray metal has left an ambiguous mark on human history.
Lead water pipes ancient Rome brought an abundance of water to the Eternal City - but also destroyed it centuries later. In ancient Greece, the mythical Bellerophon piece lead defeated the terrible chimera - but even today there are whirlwinds lead bullets are mowed down on the battlefields of soldiers, forcing them to forget about the chimeras of freedom, equality and fraternity. Inquisitors of the Middle Ages tortured and executed with molten lead- But lead typographical letters on book pages brought new knowledge and hope for freedom to a person ... Lead smelted from an ore lighter than light, but because of its exceptional softness, this metal was not destined to compete for human attention with copper, bronze and iron - neither in weapons nor in tools. It is not surprising that until the era of the Ancient Rome its use was very limited. However, they began to gradually use in ancient Egypt and Asia Minor already from the seventh millennium BC - but perhaps for the manufacture of jewelry, seals, figurines and ritual figurines. Then, from the 7th-6th centuries BC, it was mastered for the same purposes in Ancient Greece - where some miraculous properties were also attributed to it.

For example, the mythical hero Bellerophon, who saddled the winged Pegasus, contrived during a fight with the Chimera and threw an ingot into the mouth of a fire-breathing creature lead- having melted in the fiery breath of the beast, he burned its insides. The Greeks believed that this metal protected from evil witchcraft, and wore thin lead records. Lead used to make paints and even wrote on lead writing tablets.

Well, in Rome appreciated as an excellent roofing material, used it as an addition to masonry, made gutters and reservoir tanks from it. A vivid symbol of the most powerful empire of the Ancient World and evidence of the highest level of engineering and building art were the aqueducts "worked by slaves Rome» water supply.

Roman pipe production is well known - it was described in his treatises by an architect of the second half of the 1st century BC. Marcus Vitruvius Pollio, who was involved, among other things, water pipes and aqueducts. Typically outer diameter pipes was 25–27 cm with a wall thickness of 3–5 cm. They were made from cast lead sheets - first they were bent on a wooden core, then the side edges were connected, and the core was pulled out. The side seam was sealed with an alloy lead and tin - in this case, the connection could be either end-to-end or overlapping. Such pipes turned out to be oval or pear-shaped in cross-section. Vitruvius considered it most expedient to make pipes at least 3 meters long - such pipes with walls of 35 mm, they could withstand pressures of up to 10 atmospheres. After installation pipes usually embedded in masonry to ensure their airtightness.

Legendary water pipes gave Rome water abundance and unprecedented amenities - but just pipes water supply brought death to the Eternal City. The parks, who know no pity - the Roman goddesses of fate - determined with a grin that one of the main reasons for the death of the Roman Empire would be. Exactly from lead were done pipes Roman water pipelines, lead there were goblets, bottles, bowls, and even cosmetic paints were prepared using lead. The Romans preferred to store wine in lead vessels - contributed to preservation and gave the wine a sweet taste. But all soluble compounds lead poisonous!

The water that flowed through water pipelines V Rome, was rich in carbon dioxide - and it reacts with lead formed acid carbonate, soluble in water. Then entering the human body, it accumulated in it and caused chronic poisoning of the Roman nobility - with all the ensuing consequences. During sunset Rome, in the first centuries of our era, the life expectancy of noble Romans usually did not exceed 25–27 years, and many emperors suffered from mental illness. And this applied not only to the patricians drowning in luxury - running water used by everyone, from slaves to the imperial family. The Romans were sick and dying, and the great empire was dying with them. Of course it ruined Rome not just one lead abundance, decline and death of the empire caused many other objective reasons - but in the skeletons of the Romans found during excavations, scientists invariably discovered the highest content lead... But one Roman running water"Job" lead in the ancient world was not exhausted. Of course, everyone has heard of the Hanging Gardens of Babylon - one of the seven wonders of the world. These gardens were located in Babylon, on the territory of present-day Iraq, and were actually called the Hanging Gardens of Amytis - that was actually the name of the wife of the Babylonian ruler Nebuchadnezzar, for whom he in the 6th century BC. and built gardens. The riot of soaring vegetation, unthinkable for the Mesopotamian deserts, became possible only thanks to the most complex system of hydraulic structures, in the construction of which gigantic quantities were used lead.

And you won’t have to look for Russian examples for long - the well-known Vodovzvodnaya Tower of the Moscow Kremlin, when it was built in 1488, was called differently - the Sviblova Tower, after the name of the boyars, whose courtyard adjoined the tower.

And it received its current name only in 1633, after a water-lifting machine and a huge water tank lined with lead sheets. The machine pumped water from the Moscow River up into the reservoir, and from there it flowed by gravity to the “sovereign Nourishing and Feeding Palace” and the Kremlin gardens - of course, by lead pipes.

Ilya Leenson

LEAD- chemical element of group IV of the periodic table. The relative atomic mass (Ar = 207.2) is the average of the masses of several isotopes: 204Pb (1.4%), 206Pb (24.1%), 207Pb (22.1%) and 208Pb (52.4%). The last three nuclides are the end products of natural radioactive transformations of uranium, actinium and thorium. More than 20 radioactive isotopes of lead are also known, of which the longest-lived are 202Pb and 205Pb (with half-lives of 300 thousand and 15 million years). In nature, short-lived isotopes of lead are also formed with mass numbers of 209, 210, 212 and 214 with half-lives of 3.25 hours, 27.1 years, 10.64 hours and 26.8 minutes, respectively. The ratio of different isotopes in different samples of lead ores may vary slightly, which makes it impossible to determine the Ar value for lead with greater accuracy.

There is little lead in the earth's crust - 0.0016% by mass, but this one of the heaviest metals is much more widespread than its closest neighbors - gold, mercury and bismuth. This is because different isotopes of lead are the end products of the decay of uranium and thorium, so the lead content in the Earth's crust has slowly increased over billions of years.

There are many known ore deposits rich in lead, and the metal is easily separated from the minerals. In total, more than one hundred lead minerals are known. The main ones are galena (lead luster) PbS and the products of its chemical transformations - anglesite (lead sulfate) PbSO4 and cerussite (“white lead ore”) PbCO3. Less common are pyromorphite (“green lead ore”) PbCl2 3Pb3(PO4)2, mimetite PbCl2 3Pb3(AsO4)2, crocoite (“red lead ore”) PbCrO4, wulfenite (“yellow lead ore”) PbMoO4, stoltite PbWO4. Lead ores often also contain other metals - copper, zinc, cadmium, silver, gold, bismuth, etc. Where lead ores occur, the soil (up to 1% Pb), plants and water are enriched with this element.

In the highly oxidizing alkaline environment of steppes and deserts, the formation of lead dioxide - the mineral plattnerite - is possible. And native metal lead is extremely rare. See also LEAD INDUSTRY.

Story. The origin of the word "lead" is unclear. In the old days, lead was not always clearly distinguished from tin. In most Slavic languages ​​(Bulgarian, Serbo-Croatian, Czech, Polish) lead is called tin. Our “lead” is found only in the languages ​​of the Baltic group: svinas (Lithuanian), svin (Latvian). For some unfortunate translators, this led to funny misunderstandings, for example, about “tin batteries” in cars. The English name for lead, lead, and the Dutch word, lood, are probably related to our word “to tin.” The Latin plumbum (also of unclear origin) gave the English word plumber - plumber (once pipes were caulked with soft lead. And another confusion associated with lead. The ancient Greeks called lead “molybdos” (the name was preserved in the modern Greek language). Hence - Latin molibdaena: in the Middle Ages, this was the name given to both the lead sheen PbS and the rarer molybdenum sheen (MoS2), and other similar minerals that left a black mark on a light surface. The same mark was left by graphite and lead itself. Thin lead rods could be written on parchment; it’s not for nothing that in German pencil is Bleistift, i.e. lead rod.

Lead, along with gold, silver, copper, tin, iron and mercury, is one of the seven metals known since ancient times. These metals were compared with the then known planets (Saturn corresponded to lead). It is believed that people first smelted lead from ores 8 thousand years ago. Excavations in ancient Egypt have uncovered silver and lead artifacts in burials from before the dynastic period. Similar finds made in Mesopotamia date back to the same time. The joint findings of silver and lead items are not surprising. Even in prehistoric times, people's attention was attracted by beautiful heavy crystals of lead luster. Deposits of this mineral were found in the mountains of Armenia, in the central regions of Asia Minor. And the mineral galena often contains significant impurities of silver. If you put pieces of this mineral in a fire, the sulfur will burn out and molten lead will flow (charcoal prevents the oxidation of lead). Already many millennia before the new era in Mesopotamia and Egypt, statues were cast from it.

In the VI century. BC. Rich deposits of galena were discovered in Lavrion, a mountainous area near Athens. During the Punic Wars (264-146 BC), numerous lead mines operated on the territory of modern Spain, which were founded by the Greeks and Phoenicians. They were later developed by the Romans; Roman engineers used lead to make ancient water pipes. The ancient Greek historian Herodotus (5th century BC) wrote about a method of strengthening iron and bronze staples in stone slabs by filling the holes with fusible lead. Later, during excavations of Mycenae, lead staples were found in the stone walls.

When producing lead, ancient metallurgists first calcined the ore, and reactions took place

2PbS + 3O2 ® 2PbO + 2SO2 and PbS + 2O2 ® PbSO4. Then the temperature was increased, which led to the smelting of lead:

PbS + 2PbO ® 3Pb + SO2; PbS + PbSO4 ® 2Pb + 2SO2. The first smelting furnaces, made of clay and stones, were very primitive. They tried to install them on the slopes of hills, where the winds blow, helping the firing. The smelted lead, as a rule, contained silver - sometimes up to 0.5% or more. When such a melt is slowly cooled, pure lead first crystallizes, and the liquid is enriched with silver - up to about 2%. To isolate silver, the cupellation method was used: molten lead was oxidized in a porous clay vessel - a font, and its oxide was then reduced back to metal. The mechanism of this process was studied only in 1833.

Lead was also used to purify gold and silver using the cupellation method. To do this, the precious metal to be purified was fused with lead. Lead and other impurities were easily oxidized at high temperatures; the resulting oxides were blown away by an air stream, and partially absorbed into the pores of the font, and an ingot of pure silver or gold remained at the bottom. The lead oxide could then be turned back into a metal by heating it with charcoal. Archaeological finds in Ur and Troy testify that cupellation was known in the northwest of Asia Minor already in the first half of the 3rd millennium BC. And the Greek craftsmen managed to extract almost all the silver from the lead mined in Lavrion: according to modern analyzes, only 0.02% of it remained in lead! The art of the ancient metallurgists is worthy of surprise: after all, they had neither the ability to control the temperature at different stages of the process, nor to carry out chemical analyzes. Still, there was a lot of unextracted lead left in the mine dumps. Even better results were achieved by Roman metallurgists, halving the residual amount of silver. Of course, they were not worried about the purity of the lead, but about the completeness of the extraction of the precious metal from it. Moreover, as the Greek historian Strabo testifies, by processing the old dumps in Lavrion, the Romans were able to extract quite a lot of both lead and silver, leaving about two million tons of waste ore in the dumps. After that, the mines were abandoned for almost two millennia, but in 1864 they began to process the dumps again - now for the sake of only silver (about 0.01% of it remained in them). At modern metallurgical enterprises, hundreds of times less silver is left in lead.

Ancient potters, grinding lead luster with clay and water, poured this mixture over the clay vessels to be fired. At high temperatures, the surface of the vessel was covered with fusible lead glass. In 1673, the English glassmaker George Ravenscroft, adding lead oxide to the glass, invented crystal glass, which melts easily, is easy to process and has a special shine that brings it closer to real rock crystal. Later, by fusing pure white sand, potash and lead oxide, they obtained rhinestone (on behalf of the jeweler Strass, who lived at the end of the 18th century) - a type of glass with such a strong shine that it imitated diamond well, and with the admixture of various pigments - other precious stones.

Thin lead plates were used to cover the wooden hulls of ancient ships. One such Greek ship, built in the 3rd century. BC, was found in 1954 at the bottom of the Mediterranean Sea near Marseille. The Romans also made pipes from lead, 3 meters long and of different, but strictly defined diameters (there were 15 options in total). This is the first example of standardized industrial production in history. First, a plate was cast from lead, wrapped around a wooden rod, and the seam was sealed with tin-lead solder (its composition has remained virtually unchanged since then). Leaks were often found in the pipes and had to be repaired. Until now, during excavations in Italy and England, such pipes are found in very good condition. The Roman architect and engineer Marcus Vitruvius Pollio recommended replacing lead pipes with ceramic ones - made of baked clay. He drew attention to the sickness of the workers involved in lead smelting and believed that lead “deprives the blood of its strength.” However, not everyone shared this opinion. Thus, the Roman statesman, scientist and writer Pliny, author of the famous “Natural History,” wrote about the benefits of lead preparations, that lead ointment helps remove scars, heal ulcers and eye diseases.

In the Middle Ages, the roofs of churches and palaces were often covered with lead plates that were resistant to weathering. Back in 669, the roof of the monastery church in York was covered with lead, and in 688, the bishop in Northumberland ordered the roof and walls of the church to be sheathed with lead plates. The famous stained glass windows in cathedrals were assembled using lead frames with grooves in which plates of colored glass were secured. Following the example of the Romans, both water and drainage pipes were made from lead. So, in 1532, square-section lead drainpipes were installed in the Palace of Westminster. All these products in those days were not rolled, but cast in molds, on the bottom of which finely sifted sand was poured. Over time, a durable protective layer appeared on lead products - patina. Some lead-lined medieval spiers have survived for nearly seven hundred years. Unfortunately, the fire of 1561 in London destroyed such a spire of the greatest St. Peter's Cathedral.

When firearms appeared, large quantities of lead were used to make bullets and shot, and lead also began to be associated with mortal danger: “Destructive lead will whistle around me” (A. Pushkin), “For your trench, another fighter exposed his chest to evil lead” ( K. Simonov). At first, shot was cast in split molds. In 1650, the English Prince Rupert invented a faster and more convenient method. He discovered that if a little arsenic was added to lead and the alloy was poured through a kind of large colander into a tank of water, the shot balls were formed into regular spherical shapes. And after Johannes Gutenberg invented a way to print books using movable metal type in 1436, printers for hundreds of years cast letters from the so-called lead-based typographical alloy (with an admixture of tin and antimony).

Of the lead compounds, red lead Pb3O4 and basic lead carbonate (lead white) have been used since ancient times as red and white paint. Almost all the paintings of the old masters were painted with paints based on white lead. The ancient method of producing them was original: pots with strong vinegar were placed in manure, and thin lead plates twisted into a spiral were suspended above them. Decomposing, the manure produced heat (it is necessary for enhanced evaporation of acetic acid) and carbon dioxide. The combined effect of these substances on lead, as well as atmospheric oxygen, produced white. In addition to being toxic, these whites darken over time because they react with traces of hydrogen sulfide, which is always present in the air: 2PbCO3 Pb(OH)2 + 3H2S ® 3PbS + 2CO2 + 4H2O. When restoring such paintings, darkened areas are carefully treated with a solution of H2O2, which converts black sulfide into white sulfate: PbS + 4H2O2 ® PbSO4 + 4H2O. Currently, poisonous lead white has been replaced by more expensive but harmless titanium. Pigments containing lead have limited use (for example, as pigments for artistic oil paints): lemon lead crown 2PbCrO4 PbSO4, yellow lead crown 13PbCrO4 PbSO4, red lead molybdate crown 7PbCrO4 PbSO4 PbMoO4.

Properties of lead. Lead usually has a dirty gray color, although its fresh cut has a bluish tint and shines. However, the shiny metal is quickly covered with a dull gray oxide protective film. The density of lead (11.34 g/cm3) is one and a half times greater than that of iron, four times greater than that of aluminum; even silver is lighter than lead. It is not for nothing that in Russian “lead” is a synonym for heavy: “On a stormy night, darkness spreads across the sky like lead clothes”; “And how the lead sank” - these Pushkin lines remind us that the concept of oppression and heaviness is inextricably linked with lead.

Lead melts very easily - at 327.5 ° C, boils at 1751 ° C and is noticeably volatile even at 700 ° C. This fact is very important for those working at lead mining and processing plants. Lead is one of the softest metals. It is easily scratched with a fingernail and is rolled into very thin sheets. Lead is alloyed with many metals. With mercury it produces an amalgam, which, with a small lead content, is liquid.

In terms of its chemical properties, lead is a low-active metal: in the electrochemical series of voltages it stands immediately before hydrogen. Therefore, lead is easily replaced by other metals from solutions of its salts. If you dip a zinc stick into an acidified solution of lead acetate, lead is released on it in the form of a fluffy coating of small crystals, which has the ancient name “Saturn wood”. If you slow down the reaction by wrapping the zinc in filter paper, larger lead crystals grow.

The most typical oxidation state for lead is +2; lead(IV) compounds are much less stable. Lead is practically insoluble in dilute hydrochloric and sulfuric acids, including due to the formation of an insoluble film of chloride or sulfate on the surface. Lead reacts with strong sulfuric acid (at a concentration of more than 80%) to form soluble hydrosulfate Pb(HSO4)2, and in hot concentrated hydrochloric acid, dissolution is accompanied by the formation of complex chloride H4PbCl6. Lead is easily oxidized by dilute nitric acid:

Pb + 4HNO3 ® Pb(NO3)2 + 2NO2 + H2O. The decomposition of lead(II) nitrate by heating is a convenient laboratory method for producing nitrogen dioxide:

2Pb(NO3)2 ® 2PbO + 4NO2 + O2.

In the presence of oxygen, lead also dissolves in a number of organic acids. The action of acetic acid produces readily soluble acetate Pb(CH2COO)2 (the ancient name is “lead sugar”). Lead is also noticeably soluble in formic, citric and tartaric acids. The solubility of lead in organic acids could previously lead to poisoning if food was cooked in dishes tinned or soldered with lead solder. Soluble lead salts (nitrate and acetate) in water hydrolyze:

Pb(NO3)2 + H2O Pb(OH)NO3 + HNO3. A suspension of basic lead acetate ("lead lotion") has limited medical use as an external astringent.

Lead also slowly dissolves in concentrated alkalis with the release of hydrogen: Pb + 2NaOH + 2H2O ® Na2Pb(OH)4 + H2, which indicates the amphoteric properties of lead compounds. White lead(II) hydroxide, easily precipitated from solutions of its salts, also dissolves in both acids and strong alkalis:

Pb(OH)2 + 2HNO3 ® Pb(NO3)2 + 2H2O; Pb(OH)2 + 2NaOH ® Na2Pb(OH)4. When standing or heated, Pb(OH)2 decomposes to release PbO. When PbO is fused with alkali, plumbite of the composition Na2PbO2 is formed.

From an alkaline solution of sodium tetrahydroxoplumbate Na2Pb(OH)4 it is also possible to replace lead with a more active metal. If you put a small granule of aluminum into such a heated solution, a gray fluffy ball quickly forms, which is saturated with small bubbles of released hydrogen and therefore floats up. If you take aluminum in the form of a wire, the lead released on it turns it into a gray “snake”.

When heated, lead reacts with oxygen, sulfur and halogens. Thus, in a reaction with chlorine, PbCl4 tetrachloride is formed - a yellow liquid that smokes in air due to hydrolysis, and when heated, decomposes into PbCl2 and Cl2. (The halides PbBr4 and PbI4 do not exist, since Pb(IV) is a strong oxidizing agent that would oxidize bromide and iodide anions.) Finely ground lead has pyrophoric properties - it flares up in air. With prolonged heating of molten lead, it gradually turns first into yellow oxide PbO (lead litharge), and then (with good air access) into red lead Pb3O4 or 2PbO·PbO2. This compound can also be considered as the lead salt of ortholead acid Pb2. With the help of strong oxidizing agents, such as bleach, lead(II) compounds can be oxidized to dioxide:

Pb(CH3COO)2 + Ca(ClO)Cl + H2O ® PbO2 + CaCl2 + 2CH3COOH. Dioxide is also formed when red lead is treated with nitric acid:

Pb3O4 + 4HNO3 ® PbO2 + 2Pb(NO3)2 + 2H2O. If you heat brown dioxide strongly, at a temperature of about 300° C it will turn into orange Pb2O3 (PbO PbO2), at 400° C into red Pb3O4, and above 530° C into yellow PbO (decomposition is accompanied by the release of oxygen). When mixed with anhydrous glycerin, lead litharge reacts slowly over 30-40 minutes to form a waterproof and heat-resistant solid putty that can be used to glue metal, glass and stone.

Lead dioxide is a strong oxidizing agent. A jet of hydrogen sulfide directed at dry dioxide ignites; concentrated hydrochloric acid is oxidized by it to chlorine:

PbO2 + 4HCl ® PbCl2 + Cl2 + H2O, sulfur dioxide - to sulfate: PbO2 + SO2 ® PbSO4, and Mn2+ salts - to permanganate ions: 5PbO2 + 2MnSO4 + H2SO4 ® 5PbSO4 + 2HMnO4 + 2H2O. Lead dioxide is produced and then consumed during the charging and subsequent discharging of most common lead acid batteries. Lead(IV) compounds have even more typical amphoteric properties. Thus, the insoluble brown hydroxide Pb(OH)4 dissolves easily in acids and alkalis: Pb(OH)4 + 6HCl ® H2PbCl6; Pb(OH)4 + 2NaOH ® Na2Pb(OH)6. Lead dioxide, reacting with alkali, also forms a complex plumbate (IV):

PbO2 + 2NaOH + 2H2O ® Na2. If PbO2 is alloyed with solid alkali, a plumbate of composition Na2PbO3 is formed. Of the compounds in which lead(IV) is a cation, the most important is tetraacetate. It can be obtained by boiling red lead with anhydrous acetic acid:

Pb3O4 + 8CH3COOH ® Pb(CH3COO)4 + 2Pb(CH3COO)2 + 4H2O. When cooled, colorless crystals of lead tetraacetate are released from the solution. Another way is the oxidation of lead(II) acetate with chlorine: 2Pb(CH3COO)2 + Cl2 ® Pb(CH3COO)4 + PbCl2. Tetraacetate is instantly hydrolyzed with water to PbO2 and CH3COOH. Lead tetraacetate is used in organic chemistry as a selective oxidizing agent. For example, it very selectively oxidizes only some hydroxyl groups in cellulose molecules, and 5-phenyl-1-pentanol under the action of lead tetraacetate is oxidized with simultaneous cyclization and the formation of 2-benzylfuran.

Organic lead derivatives are colorless, highly toxic liquids. One of the methods for their synthesis is the action of alkyl halides on a lead-sodium alloy:

4C2H5Cl + 4PbNa ® (C2H5)4Pb + 4NaCl + 3Pb. The action of gaseous HCl can eliminate one alkyl radical after another from tetrasubstituted lead, replacing them with chlorine. R4Pb compounds decompose when heated to form a thin film of pure metal. This decomposition of tetramethyl lead was used to determine the lifetime of free radicals. Tetraethyl lead is an antiknock motor fuel.

Obtaining lead. The amount of lead mined is constantly increasing. If in 1800 about 30,000 tons were produced worldwide, then in 1850 - 130,000 tons, in 1875 - 320,000 tons, in 1900 - 850,000 tons, 1950 - almost 2 million tons, and currently per year about 5 million tons are mined. In terms of production volume, lead ranks fourth among non-ferrous metals - after aluminum, copper and zinc.

The main source of lead is sulfide polymetallic ores containing from 1 to 5% lead. The ore is concentrated to a lead content of 40 - 75%, then roasted: 2PbS + 3O2 ® 2PbO + 2SO2 and lead is reduced with coke and carbon monoxide (II). A more economical, so-called autogenous, method involves carrying out the reaction PbS + 2PbO ® 3Pb + SO2 (PbO is formed by partial roasting of PbS). Lead obtained from ore contains from 3 to 7% impurities in the form of copper, antimony, arsenic, tin, aluminum, bismuth, as well as gold and silver. Their removal (or isolation, if it is economically viable) requires complex and time-consuming operations. Lead can also be purified by electrochemical refining. The electrolyte is an aqueous solution of lead fluorosilicate PbSiF6. Pure lead is deposited at the cathode, and impurities are concentrated in the anode sludge, which contains many valuable components, which are then released.

Lead in the human body. Lead compounds are poisonous. But this did not become obvious immediately. In the past, coating pottery with lead glazes, making lead water pipes, using lead white (especially for cosmetic purposes), and using lead pipes in vapor condensers in distilleries all led to the accumulation of lead in the body. The ancient Greeks knew that wine and sour juices should not be kept in glazed clay vessels (the glaze contained lead), but the Romans ignored this rule. James Lind, who recommended lemon juice to the English Admiralty in 1753 as a remedy against scurvy for sailors on long voyages, warned against storing the juice in glazed pottery. Nevertheless, cases of poisoning, including fatal ones, were observed for the same reason two hundred years later.

Lead enters the body through the gastrointestinal tract or respiratory system and is then carried by the blood throughout the body. Moreover, inhalation of lead dust is much more dangerous than the presence of lead in food. The lead content in urban air averages from 0.15 to 0.5 μg/m3. In areas where polymetallic ore processing enterprises are located, this concentration is higher.

Lead accumulates in bones, partially replacing calcium in phosphate Ca3(PO4)2. Getting into soft tissues - muscles, liver, kidneys, brain, lymph nodes, lead causes a disease - plumbism. Like many other heavy metals, lead (in the form of ions) blocks the activity of certain enzymes. It was found that their activity decreases 100 times when the concentration of lead in the blood increases 10 times - from 10 to 100 micrograms per 100 ml of blood. In this case, anemia develops, the hematopoietic system, kidneys and brain are affected, and intelligence decreases. A sign of chronic poisoning is a gray border on the gums, a disorder of the nervous system. Lead is especially dangerous for children, as it causes developmental delays. At the same time, tens of millions of children worldwide under the age of 6 have lead poisoning; The main reason is getting paint containing lead into your mouth. The calcium salt of ethylenediaminetetraacetic acid can serve as an antidote for poisoning. In a poisoned body, calcium is replaced by lead ions, which are retained very firmly in this salt and are excreted in this form.

Lead can easily enter the body through drinking water if it has come into contact with metal: in the presence of carbon dioxide, soluble bicarbonate Pb(HCO3)2 slowly passes into solution. In ancient Rome, where lead pipes were used to supply water, such poisoning was very common, as indicated by analyzes of Roman remains. Moreover, it was mainly rich Romans who were poisoned who used running water, stored wine, olive oil and other products in leaded vessels, and used cosmetics containing lead. It is enough that there is only one milligram of lead in a liter of water, and drinking such water becomes very dangerous. This amount of lead is so small that it does not change the smell or taste of water, and only precise modern instruments can detect it.

Some historians also explain the morbidity of a number of Russian tsars with lead poisoning. In 1633, the construction of a water pipeline was completed in the Moscow Kremlin. Water came into it from a well in the lower floor of the Sviblova Tower, which stood at the confluence of the Neglinnaya and Moskva rivers. Water was pumped from the well with the help of a lifting machine - a platoon (since then this Kremlin tower has been called Vodovzvodnaya). The car was driven by horses. Water was pumped into a large tank, and from there the water itself flowed through pipes to the royal kitchen, gardens, and other places. The pipes were made of lead; The inside of the water tank was also lined with lead sheets to prevent water from leaking into the cracks. Especially a lot of lead accumulated in the water overnight, after it stood motionless in the lead tank and pipes.

The Kremlin “lead water supply” operated for a little over 100 years - it was destroyed by a fire in 1737. And during the period of operation of this water supply, the Russian tsars lived less than usual. Thus, Tsar and Grand Duke Ivan V Alekseevich, the son of Tsar Alexei Mikhailovich and his first wife, Miloslavskaya, lived only 29 years. Shortly before his death, he looked like a decrepit old man. Since childhood, he was, as they wrote then, “weak and sickly, weak in body and mind, stuttered, sad in the head, suffered from scurvy and eye disease.” Of the king's six brothers, five did not live to be 20 years old. Some scientists believe that these are the consequences of lead poisoning. But the sixth brother, Pyotr Alekseevich, the future Peter I, escaped poisoning - he spent his childhood and adolescence not in the Kremlin, but in villages near Moscow. And later he spent little time in the Kremlin - he fought a lot, traveled around Europe, and then completely moved the capital to the banks of the Neva. By the way, the first water supply system in St. Petersburg, which supplied water for the palaces and fountains of the Summer Garden, was wooden. Its pipes were made of logs with holes drilled in them. Peter used lead for military purposes - for casting bullets.

And here is how modern medical reference books write about lead poisoning: lethargy, apathy, memory loss, early dementia, weakened vision, patients look older than their years. Surprisingly reminiscent of the old description of Tsar Ivan Alekseevich!

They were once poisoned not only by “lead water”. Lead was widely used in the manufacture of dishes (lead glaze), lead white, which was used to paint the walls of houses. Now such use of lead is strictly prohibited. Whitewash, for example, is made from zinc or titanium. However, residents of industrialized countries have more lead in their bodies than residents of backward and developing countries, and urban residents have more lead than rural residents. The difference can be huge - hundreds of times.

Lead contamination began in the 20th century. global character. Even in the snows of Greenland, its content has increased fivefold over a hundred years, and in the centers of large cities there is 25 times more lead in the soil and plants than on the outskirts! Lead contamination occurs in areas where it is mined, as well as in processing areas and highways, especially if leaded gasoline is also used. A lot of lead settles at the bottom of lakes in the form of hunting shot. Every year, more than half a million tons of this toxic metal enter the World Ocean with wastewater. And who hasn’t seen used batteries thrown into trash bins, or even simply into ditches! While lead is cheap, collecting and processing its waste is unprofitable. The low solubility of most lead compounds, fortunately, does not allow it to accumulate in significant amounts in water. In the waters of the World Ocean it contains an average of 0.03 µg/l (3·10-9%). There is little lead on average in living matter - 10-4%.

Use of lead. Despite the toxicity of lead, it is impossible to avoid it. Lead is cheap - half the price of aluminum, 11 times cheaper than tin. After the French physicist Gaston Plante invented the lead accumulator in 1859, millions of tons of lead have since been used to make accumulator plates; Currently, up to 75% of all lead produced in a number of countries is used for these purposes! The use of lead for the manufacture of a very poisonous antiknock agent, tetraethyl lead, is gradually decreasing. The ability of tetraethyl lead to improve the quality of gasoline was discovered by a group of young American engineers in 1922; in their search, they were guided by the periodic table of elements, systematically approaching the most effective means. Since then, the production of tetraethyl lead has grown continuously; the maximum falls on the end of the 1960s, when hundreds of thousands of tons of lead were emitted with exhaust annually in the USA alone - one kilogram per inhabitant! In recent years, the use of leaded gasoline has been banned in many regions and its production has been declining.

Soft and ductile lead, which does not rust in the presence of moisture, is an indispensable material for the manufacture of electrical cable sheaths; Up to 20% of lead in the world is spent for these purposes. Low-active lead is used for the manufacture of acid-resistant equipment for the chemical industry, for example, for lining reactors in which hydrochloric and sulfuric acids are produced. Heavy lead is good at blocking radiation harmful to humans, and therefore lead screens are used to protect workers in X-ray rooms; radioactive drugs are stored and transported in lead containers. Babbitt bearing alloys and “soft” solders also contain lead (the most famous is “tertiary” - an alloy of lead and tin).

In construction, lead is used to seal seams and create earthquake-resistant foundations. In military equipment - for the manufacture of shrapnel and bullet cores.

Ilya Leenson

LITERATURE

A History of Technology. Vol. I - V. Oxford: Clarendon Press, 1956-1958
Chisolm J.J. Lead Poisoning. Scientific American, 1971, February
Lead. Geneva: UNIWHO Publishing House, 1980
Polyansky N.G. Lead. M., “Science”, 1986
Davydova S.L., Pimenov Yu.T., Milaeva E.R. Mercury, tin, lead and their organic derivatives in the environment. Astrakhan, 2001

Lead (Pb from the Latin Plumbum) is a chemical element that is in group IV of the Periodic Table. Lead has many isotopes, of which more than 20 have radioactive properties. Lead isotopes are decay products of uranium and thorium, so the content of lead in the lithosphere has gradually increased over millions of years and is now about 0.0016% by mass, but it is more abundant than its closest relatives such as gold and . Lead is easily released from ore deposits. The main sources of lead are galena, anglesite and cerussite. Lead often contains other metals in ore, such as zinc, cadmium and bismuth. Lead in its native form is extremely rare.

Lead - interesting historical facts

The etymology of the word “lead” has not yet been precisely clarified and is the subject of very interesting research. Lead is very similar to tin, very often they were confused, so in most Western Slavic languages ​​lead is tin. But the word “lead” is found in Lithuanian (svinas) and Latvian (svin) languages. Lead translated into English as lead, in Dutch as lood. Apparently this is where the word “tinkering” comes from, i.e. cover the product with a layer of tin (or lead). The origin of the Latin word Plumbum, from which the English word plumber is derived - plumber, is also not completely clear. The fact is that once upon a time water pipes were “sealed” with lead, “sealed” (French plomber “to seal with lead”). By the way, this is where the well-known word “filling” comes from. But the confusion does not end there, the Greeks always called lead “molybdos”, hence the Latin “molibdaena”; an ignorant person can easily confuse this name with the name of the chemical element molybdenum. This is what in ancient times they called shiny minerals that left a dark mark on a light surface. This fact left its mark in the German language: “pencil” in German is called Bleistift, i.e. lead rod.
Humanity has been familiar with lead since time immemorial. Archaeologists have found lead products smelted 8,000 years ago. In Ancient Egypt, statues were even cast from lead. In Ancient Rome, water pipes were made from lead, and it was lead that predetermined the first environmental disaster in history. The Romans had no idea about the dangers of lead; they liked the malleable, durable and easy-to-work metal. It was even believed that lead added to wine improves its taste. Therefore, almost every Roman was poisoned with lead. We will talk about the symptoms of lead poisoning below, but for now we will only point out that one of them is mental disorder. Apparently this is where all these crazy antics of noble Romans and countless crazy orgies originate. Some researchers even believe that lead was almost the main reason for the fall of Ancient Rome.
In ancient times, potters ground lead ore, diluted it with water and poured the mixture over clay objects. After firing, such vessels were covered with a thin layer of shiny lead glass.
The Englishman George Ravenscroft in 1673 improved the composition of glass by adding lead oxide to the original components and thus obtained a low-melting shiny glass that was very similar to natural rock crystal. And at the end of the 18th century, Georg Strass, when making glass, fused together white sand, potash and lead oxide, producing glass so pure and shiny that it was difficult to distinguish it from diamond. This is where the name “rhinestones” comes from, essentially a fake of precious stones. Unfortunately, among his contemporaries Strass was known as a fraudster and his invention was forgotten until, at the beginning of the 20th century, Daniel Swarovski was able to turn the production of rhinestones into an entire fashion industry and art direction.
After the advent and widespread use of firearms, lead began to be used to produce bullets and shot. Typographical letters were made from lead. Lead was previously included in white and red paints; almost all ancient artists painted with them.

Lead shot

Chemical properties of lead briefly

Lead is a matte gray metal. However, its fresh cut shines well, but unfortunately it is almost instantly covered with a dirty oxide film. Lead is a very heavy metal, it is one and a half times heavier than iron, and four times heavier than aluminum. It is not without reason that in Russian the word “lead” is to some extent synonymous with heaviness. Lead is a very fusible metal, it melts already at 327 ° C. Well, this fact is known to all fishermen who can easily melt sinkers of the required weight. Lead is also very soft and can be cut with a regular steel knife. Lead is a very low-active metal; it is not difficult to react with it or dissolve it even at room temperature.
Organic lead derivatives are very toxic substances. Unfortunately, one of them, tetraethyl lead, was widely used as an additive to gasoline to increase the octane number. But fortunately, tetraethyl lead is no longer used in this form; chemists and production workers have learned to increase the octane number in safer ways.

The effect of lead on the human body and symptoms of poisoning

Any lead compounds are very poisonous. The metal enters the body along with food or inhaled air and is carried by the blood. Moreover, inhaling lead vapors and dust is much more dangerous than its presence in food. Lead tends to accumulate in bones, partially replacing calcium in this case. When the concentration of lead in the body increases, anemia develops, the brain is affected, which leads to a decrease in intelligence, and in children it can cause irreversible developmental delays. It is enough to dissolve one milligram of lead in a liter of water and it will become not only unsuitable, but also dangerous for drinking. Such a low amount of lead also poses a certain danger; neither the color nor the taste of the water changes. Main symptoms of lead poisoning:

• gray border on the gums,
• lethargy,
• apathy,
• memory loss,
• dementia,
• vision problems,
• early aging.

Lead Applications

Still, despite its toxicity, there is no way yet to abandon the use of lead due to its exceptional properties and low cost. Lead is primarily used to produce battery plates, which currently consumes about 75% of the planet's lead. Lead is used as a sheath for electrical cables due to its ductility and resistance to corrosion. This metal is widely used in the chemical and oil refining industries, for example, for lining reactors in which sulfuric acid is produced. Lead has the property of blocking radioactive radiation; this is also widely used in energy, medicine and chemistry. For example, radioactive elements are transported in lead containers. Lead is used to make bullet cores and shrapnel. This metal also finds its application in the production of bearings.

Lead statue of St. Martin in Bratislava