Lead is a metal that was known inancient times. Man uses it from 2-3 thousand BC, and for the first time it was opened in Mesopotamia. There from the lead made small bricks, statuettes, various household items. Even then people received bronze using this element, and also made of this metal plates for writing with sharp objects.
It is an element of group IV of period 6 of the tableMendeleyev, where he has the ordinal number 82. What is lead in nature? This is the most common galena, the formula of which is PbS. Otherwise, galena is called lead gloss. The clean element is a soft and malleable metal of dirty gray color. In air, its cut 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 covered with oxides is cleaned, it will acquire a brilliant shade with a blue tint. Such purification can be done if the lead is poured in a vacuum and it is sealed in a vacuum flask.
Sulfuric and hydrochloric acids act on leadvery weak, but the metal dissolves easily in nitric acid. All chemical compounds of the metal, which can be soluble, are poisonous. It is obtained mainly from ores: first, the lead gloss is fired before the transition to lead oxide, and then this substance is reduced by means of coal to pure metal.
The lead density is 11.34 g / cm3. This is 1.5 times greater than the density of iron and infour times more than that of light aluminum. Not for nothing in Russian, the word "lead" is synonymous with the word "heavy". Lead melting occurs at a temperature of 327.5 aboutFROM. Volatile metal is already at an ambient temperature of 700 ° C. This information is very important for those who work in the field of obtaining this metal. It is very easy to scratch with a fingernail, it is easy to roll into thin sheets. It's a very soft metal.
The specific heat of lead is 140 J / kg. In terms of its chemical properties, it is a low-active metal. In the series of stresses, it is located in front of the hydrogen. Of its salts, lead is easily replaced by other metals. For example, you can conduct an experiment: drop the stick from zinc into the acetate solution of this element. Then he will settle on a zinc stick in the form of fluffy crystals, which the chemists call a "Saturn tree." How much is the specific heat of lead equal to? What does this mean? This figure is 140 J / kg. And it means the following: to heat a kilogram of metal by 1 aboutC, requires 140 Joule heat.
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 different lead isotopes are products of the decomposition of thorium and uranium, so the lead content in the earth's crust has slowly increased over millions of years. At the moment, there are many known lead ores - this is already galena, as well as the results of its chemical transformations.
The latter includes lead sulphate, cerussite(another name - white lead ore), mimetite, stolcite. The ore also contains other metals - cadmium, copper, zinc, silver, bismuth. Wherever lead ores occur, this metal is saturated not only with soil, but with reservoirs and plants. What is lead in nature? It is always his definite connection. And also this metal is contained in the ores of radioactive metals - uranium and thorium.
The most used in industry iscompound of lead and tin. Ordinary soldering under the name "tractor" is widely used for connections of pipelines and electric wires. This compound contains one part of lead and two parts of tin. Shells for telephone cables, parts of batteries can also contain lead. The melting point of some of its compounds is very low - for example, alloys with cadmium or tin melt at 70 aboutFROM. Of these compounds, fire fighting equipment is manufactured. Alloys of metal in shipbuilding are widely used. They are usually painted in a light gray color. Vessels are often covered with tin and lead alloys to protect them from corrosion.
The Romans used this metal to makepipes in pipelines. Lead in ancient times was associated with people with the planet Saturn, and therefore before it was 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 continued until the 17th century. And in the ancient Slavic languages, he also had this name.
It reached the modern Czech language, wherethis heavy metal is called olovo. Some experts in the field of linguistics believe that the name Plumbum is associated with a certain Greek terrain. The Russian origin of the word "lead" for scientists is still unclear. Some linguists associate it with the Lithuanian word "scwinas".
The traditional use of lead in history ismaking bullets, weapons shot, and other various shells. It was used because of the low cost and low melting point. Earlier, when making weapons shot, a small amount of arsenic was added to the metal.
Lead was used in ancient Egypt. From it, building blocks, statues of noblemen were made, coins were coined in all. The Egyptians were confident that lead has a special energy. They made small plates out of it and used them to protect themselves from ill-wishers. And the ancient Romans not only made water pipes. They also made cosmetics from this metal, even without realizing that they themselves are signing this death sentence. After all, getting into the body every day, lead caused serious diseases.
There are substances that kill humanityslowly but surely. And this applies not only to the unenlightened ancestors of antiquity. Sources of toxic lead today are cigarette smoke, city dust of apartment buildings. A couple of paints are also a danger. But the greatest harm is borne by the exhaust gases of automobiles, in large quantities containing lead.
But in the risk zone are not only residentsmegacities, 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 used regularly, you can safely disinfect yourself from the harmful effects of metal.
Every schoolboy knows what lead is. But not all adults are able to answer the question about what is his harm. Particles of it enter the body through the respiratory system. Next, he begins to interact with the blood, reacting with various parts of the body. Most of all, the musculoskeletal system suffers from this. Here it is 95% of the total lead consumed by man.
High level of its content in the bodyleads to a lag in mental development, and in adults it manifests itself in the form of depressive symptoms. On the excess is evidence of absent-mindedness, fatigue. The intestines suffer too - spasms can often occur because of lead. This heavy metal also negatively affects the reproductive system. Women find it difficult to bear fruit, and men may have problems with sperm quality. It is also very dangerous for the kidneys. According to some studies, it can cause malignant tumors. However, in an amount not exceeding 1 mg, lead can be useful for the body. Scientists have found out that this metal can have a bactericidal effect on the organs of vision - but it should be remembered that such lead and use it only in doses not exceeding permissible.
As already mentioned, in ancient times the patronThis metal was considered the planet Saturn. But Saturn in astrology is an image of loneliness, sadness and a heavy fate. Is not that why lead is not the best companion for man? Perhaps, he should not impose his society, as the ancients intuitively assumed, calling the lead Saturn. After all, damage to the body from this metal can be irreparable.
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