The ancients employed quicksilver to generate red mercuric oxide by heating the element in a nitric acid solution. A dense red mist floats over the surface of the quicksilver in nitric acid reaction, and vivid red crystals precipitate to the bottom. Mercury, alchemists believed, could travel between solid and liquid phases, between earth and heaven, between life and death.
Mercury is one of alchemy’s seven metals (gold, silver, mercury, copper, lead, iron & tin). Mercury’s symbol might also be used to signify the astrological planet of the same name. A serpent or snake is frequently used to represent the metal.