Properties and application areas of mercury

physical properties

It is the only metal that exists in a liquid state at normal temperature and pressure. The melting point is -38.87℃, the boiling point is 356.6℃, and the density is 13.59g/cm3. It has strong cohesion and is stable in the air. Mercury vapor evaporates at room temperature, and the vapor is highly toxic. Natural mercury is a mixture of seven isotopes of mercury. Mercury is slightly soluble in water, and its solubility increases in the presence of air. Mercury is ubiquitous in nature. Generally, animals and plants contain trace amounts of mercury. Therefore, trace amounts of mercury exist in our food, which can be metabolized through excretion and hair.

Alloys: Mercury readily forms alloys with most common metals, and these alloys are collectively known as amalgams (or amalgams). Metals that can alloy with mercury include gold and silver, but not iron, so iron powder has long been used to replace mercury. Some other first row transition metals are difficult to alloy, but do not include manganese, copper and zinc. Other elements that do not easily alloy with mercury are platinum and some other metals. Sodium amalgam is a commonly used reducing agent in organic synthesis and is also used in high pressure sodium lamps. When mercury and pure metal of aluminum come into contact, they tend to form aluminum amalgam, because aluminum amalgam can destroy the oxide layer that prevents further oxidation of metal aluminum (brush test), so even small amounts of mercury can severely corrode metal aluminum . For this reason, mercury cannot, in the vast majority of cases, be carried on an aircraft because it can easily alloy with exposed aluminum parts of the aircraft and pose a hazard.

Liquid: Mercury, a metal, exists in a strange liquid state at room temperature. The theory of relativistic contraction effects can provide an explanation for this unusual phenomenon. Similar to gold, the shrinking and stabilizing of mercury’s 6s orbital leads to a so-called “inert electron pair” effect: the mercury’s 6s2 shell is rendered inert during bonding. It can be seen that the 6s26p excitation energy of mercury far exceeds the corresponding excitation energy of cadmium and zinc. According to the general periodic law, the energy interval should decrease with the increase of the principal quantum number. Therefore, the narrowing of the energy interval from Zn to Cd is expected, whereas the energy interval increases abruptly from Cd to Hg. Here it can be seen again that it is the relativistic contraction effect that makes the fully filled 6s2 shell stable and stable, so the 6s26p energy interval of mercury increases sharply. As long as the desired excitation energy is not obtained, strong bonds cannot be formed between mercury atoms with inert 6s2 shells. The ground state Hg2 is only mutually maintained by van der Waals forces, so metallic mercury is liquid at room temperature.

Introduction to Toxicology

It should be noted that ingestion of trace amounts of liquid mercury generally does not cause serious poisoning [8] (there is information that it will form organic compounds in living organisms), but mercury vapor and mercury salts (except for some extremely soluble such as sulfur Mercury) are highly toxic and can cause brain and liver damage by ingestion, inhalation, or exposure. The use of thermometers generally replaces mercury with alcohol, and mercury is still used in thermometers used in the People’s Republic of China (excluding Hong Kong, Macao and Taiwan). China plans to phase out the use of mercury thermometers by 2015.
The most dangerous mercury organic compound is dimethyl mercury [(CH3)2Hg], and only a few microliters (10-9m3 or 10-6dm3 or 10-3cm3) of dimethylmercury can be lethal on skin.
Mercury can accumulate in the body and is easily absorbed by the skin as well as the respiratory and digestive tracts. Minamata disease is a type of mercury poisoning. Mercury damages the central nervous system and has adverse effects on the mouth, mucous membranes and teeth. Prolonged exposure to high levels of mercury can cause brain damage and death. Despite the high boiling point of mercury, the saturated mercury vapor at room temperature has reached several times the toxic dose.

Medicinal field

Mercury comes from the “Benjing”. “The Book of Sketches”: Mercury, the “Sutra” says that cinnabar is derived from cinnabar, which is coarse cinnabar mined from mountains and rocks, used as a furnace and placed in the middle, with water on the bottom, and ounces on the top. Flying above, the mercury slips below, its color is small and turbid. As for those who came from the Western Qiang, they also said that they were calcined in this way. But there are a lot of things born in the mountains. As for a mountain that is torn apart by itself, people pick up sand and gravels, all of which are big like buckets. The broken pieces can be sintered. Therefore, the mercury from the west is much more than that from the south. “Materia Medica Yanyi”: mercury, when lead is condensed, when sulfur is obtained, it is knotted, and when jujube meat is ground, it is scattered. Other methods are calcined into greasy powder and powder cream. Saliva research dead lice. “Outline”: Mercury, if it is scattered on the ground, it is collected with Sichuan pepper powder or tea powder. “Benjing meets the original”: Mercury, sinister and poisonous, should not enter the stomach. Today, I have mistakenly ingested mercury, and my belly has fallen heavily. I use 2 catties of lard, cut it into small pieces, bake it, and mix it with raw honey. It is also the same method.
pharmacological action

  1. Mercury (mercury) compounds have sterilizing, diarrhea, and diuretic effects, which are no longer used or rarely used. Elemental mercury does not cause pharmacological effects, and the dissociated mercury ions can combine with sulfhydryl groups to interfere with the metabolism and function of cells. Elemental mercury cannot be absorbed from the gastrointestinal tract, but its surface can form oxides or sulfides when exposed to air, which can sometimes cause mild diarrhea and diuresis after swallowing. Most people who swallow mercury are asymptomatic. Mercury is excreted in the feces, a few people may have some symptoms, and very few (sensitivity or other unknown causes) can cause immediate death.
  2. Mercury is a protoplasmic poison, which can combine with the sulfhydryl groups in the respiratory enzymes of pathogenic microorganisms to inhibit their viability, and finally make them suffocate and die.
  3. Mercury is excreted mainly by the kidneys, followed by the large intestine.
    Pharmacology (Toxicology)
    Mercury has a corrosive effect on the digestive tract and damages the kidneys and capillaries. Acute poisoning is mostly caused by mistaken ingestion of mercuric chloride, and there are symptoms caused by corrosion of the digestive tract. After absorption, kidney damage will occur, resulting in urinary retention and capillary damage, resulting in plasma loss and even shock. Early application of dimercaptopropanol and other symptomatic measures are mostly effective. Chronic poisoning is generally seen in industrial poisoning, stomatitis and toxic encephalopathy, the latter manifested as depression, cringe and other mental symptoms and muscle tremors.
chemical properties

Dissolved in nitric acid and hot concentrated sulfuric acid, it generates mercuric nitrate and mercuric sulfate, respectively, and mercurous salts appear in excess of mercury. It can dissolve many metals and form alloys, which are called amalgam. The valences are +1 and +2. Similar to silver, mercury can also react with hydrogen sulfide in the air. Mercury has a constant coefficient of volume expansion, is less metal active than zinc and cadmium, and cannot displace hydrogen from acid solutions. Generally, the valence of mercury compounds is +1 or +2. Mercury compounds with a valence of +4 have only mercury tetrafluoride, and mercury compounds with a valence of +3 do not exist.

Application field

The most common applications of mercury are in the manufacture of industrial chemicals and in electronic or electrical products. Mercury is also used in thermometers, especially those that measure high temperatures. More and more gaseous mercury is still used to make fluorescent lamps, while many other applications are being phased out due to health and safety concerns in favor of the less toxic but much more expensive Galinstan alloy. Other uses of mercury include:
Gold can be decomposed from its minerals, so it is often used in gold mining.
Used to make instruments such as barometers and diffusion pumps.
Gaseous mercury is used in mercury vapor lamps.
Used in the manufacture of liquid mirror telescopes. A telescope that uses rotation to make the liquid form a parabolic shape and uses it as the main mirror for astronomical observation is one-third the price of ordinary telescopes.
Other uses: Mercury switches, pesticides, in the production of chlorine and potassium hydroxide, as a preservative, as electrodes, batteries and catalysts in some electrolysis equipment.
Amalgam dental fillings.
Mercury and its compounds have always been used in medicine, though not as often as they used to be because the toxicity of mercury and its compounds has become more widely known. Mercury is an important element in making dental fillings. Thimerosal is an organic preservative used in vaccines, although its use has been banned. Another mercury compound, mercuric bromide, is a topical disinfectant used for minor cuts and superficial wounds; it is still used in some countries.
Thiomersal is widely used in the manufacture of eyebrow tinted creams. In 2008, Minnesota became the first U.S. state to ban mercury in cosmetics.

Disposal of leaks

The widely used thermometers and sphygmomanometers have caused environmental problems such as mercury contamination indoors. If you break the mercury thermometer indoors, don’t panic. You can immediately use a piece of paper to remove the broken mercury beads that are visible to the naked eye (due to the high cohesion of mercury, use a cotton swab). It is extremely unscientific and irresponsible to say that it cannot be contaminated with mercury.) Hold it up and put it in a sealed water bottle. If there are small mercury beads, they can be pushed together with a piece of paper, and the mercury will automatically gather into small balls, and then collect . To be safe, nitric acid can be used to wipe down mercury-contaminated floors with some simple chemicals to completely remove mercury contamination. The reaction of mercury and sulfur can be carried out without heating. Therefore, the scattered mercury can be covered with sulfur powder to combine sulfur and mercury to form HgS, preventing mercury vapor from entering the air and causing poisoning. In order to completely remove mercury pollution, the room can also be fumigated by iodine vapor fumigation several times until the cuprous iodide test paper does not change color. Experiments have shown that the daily leaked mercury can be glued and collected with the commonly used scotch tape in the family, and the effect is better than that of paper.