Mercury (chemical element)

Mercury . Chemical element, symbol Hg, atomic number 80 and atomic weight 200.59. It is a silvery white liquid at room temperature (melting point -38.4ºC or -37.46ºF); boil at 357ºC (675.05ºF) at atmospheric pressure. It is a noble metal , soluble only in oxidizing solutions. Solid mercury is as soft as lead. The metal and its compounds are highly toxic. Mercury forms solutions called amalgams with some metals (for example, gold , silver , platinum , uranium , copper , lead , sodium, and potassium ).

Summary

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  • 1 Mercury compounds
  • 2 Effects of mercury on health
  • 3 Environmental effects of mercury
  • 4 See also
  • 5 Sources

Mercury compounds

In its compounds, mercury is found in oxidation states 2+, 1+, and lower; for example, HgCl2, Hg2Cl2, or Hg3 (AsF6) 2. Mercury atoms often have two covalent bonds; for example, Cl-Hg-Cl or Cl-Hg-Hg-Cl. Some salts of mercury (II), for example, Hg (NO3) 2 or Hg (ClO4) 2, are highly soluble in water and are generally dissociated. Aqueous solutions of these salts react like strong acids because of the hydrolysis that occurs.

Other salts of mercury (III), such as HgCl2 or Hg (Cn) 2, also dissolve in water, but in solution they are only slightly dissociated. There are compounds in which the mercury atoms are directly linked to carbon or nitrogen atoms; for example, H3C-Hg-CH3 or H3C-CO-NH-Hg-NH-CO-CH3. In complexes, such as K2 (HgI4), it often has three or four bonds.
Metallic mercury is used in electrical switches as a liquid contact material, as a working fluid in diffusion pumps in vacuum techniques, in the manufacture of mercury vapor rectifiers, thermometers, barometers, tachometers and thermostats, and in the manufacture of lamps. of mercury vapor.

It is used in silver amalgams for tooth fillings. Normal calomel electrodes are important in electrochemistry; they are used as reference electrodes in the measurement of potentials, in potentiometric titrations and in the normal Weston cell.

Mercury is commonly found as its sulfide HgS, often as cinnabar red, and less abundantly as black metalcinnabar. A less common mineral is mercury (I) chloride. Mercury minerals sometimes contain tiny droplets of metallic mercury.
The surface tension of liquid mercury is 484 dynes / cm, six times that of water in contact with air. Therefore, mercury cannot wet any surface with which it comes in contact. In dry air metallic mercury does not oxidize, but after long exposure to humid air the metal becomes covered with a thin oxide film. It does not dissolve in free air hydrochloric acid or dilute sulfuric acid, but it does dissolve in oxidizing acids (nitric acid, concentrated sulfuric acid, and aqua regia).

Health effects of mercury

Mercury is an element that can be found naturally in the environment. It can be found in the form of metal, as mercury salts or as organic mercury.
Metallic mercury is used in a variety of household products, such as barometers, thermometers, and fluorescent bulbs. The mercury in these mechanisms is trapped and usually does not cause any health problems. Either way, when a thermometer breaks, a significantly high exposure to mercury occurs through respiration, this will occur for a short period of time while it evaporates.

This can cause harmful effects, such as nerve, brain, and kidney damage, lung irritation, eye irritation, skin reactions, vomiting, and diarrhea .
Mercury is not found naturally in food, but it can appear in food as well as be spread in food chains by small organisms that are consumed by humans, for example through fish.

Mercury concentrations in fish usually greatly exceed concentrations in the water where they live. Livestock products can also contain significant amounts of mercury. Mercury is not commonly found in plants, but it can enter human bodies through vegetables and other crops. When sprays containing Mercury are applied in agriculture.

Mercury has a number of effects on humans, which can all be simplified into the following mainly:

  • Damage to the nervous system
  • Damage to brain functions
  • DNA and chromosome damage
  • Allergic reactions, skin irritation, tiredness, and headache
  • Negative effects on reproduction, sperm damage, birth defects and abortions.

Damage to brain functions can lead to impaired ability to learn, personality changes, tremors, vision changes, deafness, muscle incoordination, and memory loss. Chromosome damage and known to cause Mongolism.

Environmental effects of mercury

Mercury enters the environment as a result of the breakdown of minerals in rocks and soils through exposure to wind and water. The release of Mercury from natural sources has remained at the same level over the years.

Mercury concentrations in the environment are still growing; This is due to human activity. Most of the mercury released by human activities is released into the air , through the burning of fossil products, mining, smelting, and combustion of solid waste.
Some forms of human activities release mercury directly to the soil or water , for example the application of fertilizers in agriculture and industrial wastewater discharges. All the Mercury that is released into the environment will eventually end up in soil or surface waters. Mercury from the soil can accumulate in mushrooms.
Acidic surface waters can contain significant amounts of mercury.

When the pH values ​​are between five and seven, the concentrations of mercury in the water will increase due to the mobilization of mercury in the soil.
Mercury that has reached surface waters or soils can be converted by microorganisms into methyl mercury, a substance that can be absorbed rapidly by most organisms and is known to damage the nervous system .

Fish are organisms that absorb large amounts of methyl mercury from surface water every day. As a consequence, methyl mercury can accumulate in fish and in the food chains of which they are a part.
The effects of mercury in animals are kidney damage, stomach disorders, intestinal damage, reproductive failure, and DNA damage .

 

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