first mention of mercury have survived are dated about V century BCIn those days it was extracted only known then the way - by roasting cinnabar (a compound with sulfur), along with coal.Upon heating cinnabar breaks down its mercury and sulfur, the latter combines with oxygen and forms a volatile compound.At room temperature, the mercury density (kg / m3) of 13 545.7 kilograms per cubic meter, with it - the only metal that we observe in normal conditions in a liquid state.
In nature, the relative density of mercury is low and is estimated at approximately 0.03 - 0.09 mg per kilogram of rock.Concentrated deposits are rare, mainly mercury compounds are literally scattered all over the near-surface layer of the earth's crust.Worldwide there are about 5000 deposits of this metal, which is subjected to the development of only about 500. According to modern science, a much higher density of mercury (relative to other components) was observed in the Earth's mantle, where it gets to the surface and into the atmosphere during volcanic eruptions,earthquakes, tectonic faults etc.The so-called breathing of the planet mercury evaporates from the depths of the order of 3 000 tons of mercury per year;humanity (if you believe the scientists estimated) adds to this the approximately 4 000 tonnes per year.In planetary scale value may seem small, however, should take into account the extremely low solubility of most mercury compounds, because they almost eliminated from the body.
ability of heavy metals to the gradual accumulation - a very unpleasant feature, especially when you consider that they are stored not only in humans but also in the tissues of animals, serving our food.The relative density of mercury accumulated in the body of the animal, not the same for different species;In addition, the influence habitat and age.For example, fish predators gradually accumulate in their tissues a compound containing mercury;the density of these compounds as the life of the predators is growing faster than the fish-eating plant foods.This factor must be considered, especially if the body of water where caught fish exposed to sewage.Similar conclusions are also valid for the terrestrial species of animals and birds.
Despite the high toxicity of mercury, the rejection of its use is hardly possible.Probably the best known of its application in medical thermometers (good combination of: Medicine and frank poison).The use of mercury in measuring the temperature is dictated by its extraordinarily advantageous combination of properties: 1) a large range of temperature measurement;2) more uniform than with other liquids, extensibility (which can improve the accuracy of measurement);3) a complete lack of wet glass mercury;4) low heat capacity, providing quick response thermometer to changes in external conditions.
No less widespread should be called fluorescent lamps, in which the radiation is generated by the action of mercury vapor glow discharge.Usually the density of mercury (more precisely, its vapor) in the lamp bulb is small, the ground pressure is generated with an inert gas.Visible light appears through the phosphor deposited on the surface of the glass: mercury vapor ultraviolet radiation is completely absorbed and the energy is redistributed in the visible range.The quality of light (color, continuity of the spectrum) depends upon the specific composition of the phosphor.For residential premises is recommended to choose a lamp with a warm light (or a combination of warm light and daylight in the set) for the office is the best day, that is,a little more cool lighting.
