You must have heard about quicksilver. Did you know it’s the same thing as the chemical element mercury? It was known as quicksilver because in fact this is what it looks like to the naked eye: like a running silvery liquid.
Mercury is a fascinating metal. Not quite the only one to be liquid (bromine, gallium, caesium and rubidium are also liquid), it is however the only one that is liquid at normal temperature and pressure. Its chemical symbol in the table of elements is Hg, which comes from the Greek term hydrargyrum (literally quicksilver); its current name comes from the planet Mercury.
Mercury is not found as such in nature, but rather has to be mined out from cinnabar deposits. It easily forms bonds with other metals, such as silver or gold; what this means is that it could be used to form, for instance, silver and mercury amalgams that were widely used in dentistry as fillings. What this also means is that it was not easy to find a metal container for carrying mercury, as most metals will be dissolved in contact with it. Iron is an exception.
Mercury is a good conductor of electricity, and was for a long time thought to have medicinal qualities (which were later, for the most part, refuted by science or counter-weighed by its toxic effects.)
The use of mercury has been severely cut down in the past years, especially in more advanced countries. However, in many places it is still not fully regulated and therefore still present on the market in various products:
The reason for the removal of mercury from most products commercially available in the U.S. is that numerous studies have confirmed its great toxicity. Because mercury can be present in many forms – metal, vapor or salt – and in many compounds, we may not always be aware that contact has taken place. However, mercury can be inhaled or absorbed through the skin, and mercury poisoning is extremely dangerous. The phrase "mad as a hatter" comes from a historical fact: for a few centuries, up to the 19th century, hatters used a mercury nitrate compound in the treatment of the pelts and materials used for the making of hats. As a result, they displayed symptoms of "madness", i.e. of mercury poisoning: