IYPT 2019 Elements 080: Mercury: Liquid metal and potent poison

Element 80 in our International Year of the Periodic Table series is mercury. Mercury is the only metal which is liquid at room temperature and has a reputation for toxicity.

Mercury melts at –39˚C, making it the only metal in the periodic table which is liquid at room temperature. The fact that mercury’s a liquid while the other metals around it in the table aren’t is down to relativity. The only other element in the periodic table which is liquid at room temperature is bromine.

Mercury and many of its compounds are toxic to varying degrees. Elemental mercury isn’t well absorbed when digested or in contact with the skin. However, it is toxic if inhaled as a vapour. Methylmercury is the major source of mercury exposure for most people; it is found in varying amounts in different types of fish. The quantities are at levels which are generally considered safe, but some groups of people, such as pregnant women, are advised to limit their fish consumption as a consequence.

Before mercury’s toxic effects were known, the use of mercury compounds in some professions commonly led to poisoning. One of the most well-known cases of this was in the hat-making profession. Hatters used mercury(II) nitrate in the process of making hat felt, and the symptoms of the poisoning gave them symptoms attributed to madness – hence ‘mad as a hatter’.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.