Lead is a metal that was known in ancient times. Man uses it from 2-3 thousand BC, and for the first time it was discovered in Mesopotamia. There, small bricks, statuettes, and various household items were made from lead. Even then, people received bronze with this element, and also made tablets for writing with sharp objects from this metal .
What color does the metal have?
It is an element of group IV of the 6th period of the periodic table, where it has serial number 82. What is lead in nature? This is the most common galena, the formula of which is PbS. Otherwise, galena is called lead shine. The clean element is a soft and malleable metal of dirty gray color. In the air, its section is quickly covered with a small layer of oxide. Oxides reliably protect the metal from further oxidation in both wet and dry environments. If the metal surface coated with oxides is cleaned, it will acquire a brilliant shade with a blue tint. Such cleaning can be done if the lead is poured in a vacuum and sealed in a vacuum flask.
Acid interaction
Sulfuric and hydrochloric acids act very poorly on lead, but the metal is easily soluble in nitric acid. All chemical compounds of a metal that may be soluble are toxic. It is obtained mainly from ores: first, the lead luster is fired before converting to lead oxide, and then this substance is reduced with the help of coal to a pure metal.
General item properties
The density of lead is 11.34 g / cm 3 . This is 1.5 times more than the density of iron and four times more than that of light aluminum. It is not without reason that in Russian the word “lead” is a synonym for the word “heavy”. Lead melts at a temperature of 327.5 ° C. The metal becomes volatile even 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 it even with a fingernail; it is easy to roll into thin sheets. This is a very soft metal.
Interaction with other metals, heating
The specific heat of lead is 140 J / kg. By its chemical properties it is a low-activity metal. In a series of stresses, it is located in front of hydrogen. Lead is easily superseded by other metals from its salts. For example, you can conduct an experiment: dip a zinc stick into a solution of the acetate of this element. Then he will settle on a zinc stick in the form of fluffy crystals, which chemists call the "Saturn tree." How much is the specific heat of lead equal to? What does this mean? This indicator is 140 J / kg. So it means the following: to heat a kilogram of metal by 1 ° C, 140 Joules of heat are required.
Spread in nature
This metal is not so much in the earth's crust - only 0.0016% by weight. However, even this value shows that it is more common than mercury, bismuth and gold. Scientists attribute this to the fact that various lead isotopes are the decay products of thorium and uranium, so the lead content in the earth's crust has slowly increased over millions of years. At the moment, many lead ores are known - this is the indicated galena, as well as the results of its chemical transformations.
Content in nature: part of the ore
The latter include lead vitriol, cerussite (another name is white lead ore), mimetite, stolzite. Ores also contain other metals - cadmium, copper, zinc, silver, bismuth. Where ore from lead is deposited, not only the soil is saturated with this metal, but also water bodies and plants. What is lead in nature? It is always its definite mix. And also this metal is contained in ores of radioactive metals - uranium and thorium.
Heavy metal in industry
The most used in industry is a compound of lead and tin. An ordinary solder called tertiary is widely used for connecting pipelines and electrical wires. This compound contains one part of lead and two parts of tin. Jackets for telephone cables, battery parts 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 ° C. Fire-fighting equipment is made from such compounds. Metal alloys are widely used in shipbuilding. They are usually light gray. Vessels are often coated with tin and lead alloys to protect against corrosion.
Significance for people of the past and application
The Romans used this metal to make pipes in pipelines. In ancient times, lead was associated in humans with the planet Saturn, and therefore it used to be called Saturn. In the Middle Ages, due to its heavy weight, metal was often used for alchemical experiments. He was often credited with the ability to turn into gold. Lead is a metal that is often confused with tin, which lasted until the 17th century. And in ancient Slavic languages he bore this name.
It has reached the modern Czech language, where this heavy metal is called olovo. Some experts in the field of linguistics believe that the name Plumbum is associated with a particular Greek locality. The Russian origin of the word “lead” is not yet clear to scientists. Some linguists associate it with the Lithuanian word “scwinas”.
The traditional use of lead in history is the manufacture of bullets, shotguns, and various other shells. It was used because of its low cost and low melting point. Previously, in the manufacture of shotguns, a small amount of arsenic was added to the metal.
Lead was also used in ancient Egypt. It made building blocks, statues of noble people, minted coins in full. The Egyptians were convinced that lead has a special energy. They made small plates from it and used them to protect them from ill-wishers. And the ancient Romans not only made water pipes. They also made cosmetics from this metal, not even suspecting that they themselves signed a death sentence for themselves. After all, getting into the body every day, lead caused serious diseases.
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, urban dust from residential buildings. Fumes of paints and varnishes are also dangerous. But the greatest harm is caused by the exhaust gases of cars that contain lead in large quantities.
But not only residents of megacities are at risk, but also those who live in villages. Here, metal can accumulate in soils, then fall into the composition of fruits and vegetables. As a result, a person receives 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. Then it begins to interact with blood, entering into reactions with various parts of the body. The musculoskeletal system suffers the most from this. It turns out 95% of all lead consumed by man.
A high level of its content in the body leads to a lag in mental development, and in adults it manifests itself in the form of depressive symptoms. The excess is indicated by distraction, fatigue. The intestines also suffer - cramps can often occur due to lead. This heavy metal also negatively affects the reproductive system. It becomes difficult for women to bear the fetus, while 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 quantities not exceeding 1 mg, lead may 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 not exceeding the permissible ones.
In conclusion
As already mentioned, in ancient times the planet Saturn was considered the patron saint of this metal. But Saturn in astrology is an image of loneliness, sadness and hard fate. Is that why lead is not the best companion for man? Perhaps he should not impose his society, as the ancients intuitively suggested, calling lead saturn. After all, harm to the body from this metal can be irreparable.