Last revised by Daniel J Bell on 22 Dec 2020

Mercury (chemical symbol Hg) is a liquid metallic element that historically was used in many medicines, but is now restricted due to legitimate concerns about mercury poisoning which is primarily found in seafood.

Mercury is a silvery liquid at standard temperature and pressure. It has the atomic number 80 and an atomic weight of 200.592. 

Mercury exists in multiple stable isotopes on earth; mercury-202 is the most abundant, forming 29.7%, mercury-200 accounts for another 23.1%. Mercury-199, mercury-201, and mercury-198, account for 16.9%, 13.1%, and 10% respectively. Mercury-204 forms 6.8% of the total. Many other radioactive mercury isotopes are known, many with very short half-lives 3.

Unfortunately mercury demonstrates marked toxicity, see main article on mercury poisoning. The prototypical condition of mercury toxicity is Minamata disease.

  • mercury has been a key ingredient for dental amalgam for many years, the elemental mercury is alloyed with other metals including silver, tin, copper, and occasionally zinc. It forms a silvery paste which is used to fill the carious cavity, which then sets to form a hard permanent dental filling.
  • thimerosal, an organomercury antiseptic agent was for decades used as the main preservative in vaccines, but has now been largely phased out due to concerns about its toxicity
    • thimerosal is still used as a topical antiseptic for some applications
  • mercury-197 and mercury-203 were historically used as radiotracers in renal imaging

Mercury has been known about since prehistoric times. It was named quicksilver by Aristotle (384-322 BCE) and liquid silver by Dioscorides (40-90 CE) 4

Historically mercury was a popular treatment for sexually-transmitted infections, in particular syphilis, but was abandoned many years ago due to mercury's inherent toxicity 4.

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Cases and figures

  • Figure 1: mercury (photo)
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  • Figure 2: periodic table
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