Alchemical symbol
Alchemical symbols, originally devised as part of alchemy, were used to denote some elements and some compounds until the 18th century. Although notation like this was mostly standardized, style and symbol varied between alchemists, so this page mainly lists the most common ones. Three primes. According to Paracelsus (1493–1541), the three primes or "tria prima" – of which material substances are immediately composed – are: Four basic elements. Western alchemy makes use of the four classical elements. The symbols used for these are: Seven. The seven metals known since Classical times in Europe were associated with the seven classical planets ; this figured heavily in alchemical symbolism. The exact correlation varied over time, and in early centuries bronze or electrum were sometimes found instead of mercury, or copper for Mars instead of iron, though gold, silver and lead had always been associated with the Sun, Moon and Saturn. The associations below are attested from the 7th century and had definitely stabilized by the 15th. They started breaking down with the discovery of antimony, bismuth and zinc in the 16th century. Alchemists would typically call the metals by their planetary names, e.g. "Saturn" for lead and "Mars" for iron; compounds of tin , iron and silver continued to be called "jovial", "martial" and "lunar"; or "of Jupiter", "of Mars" and "of the moon", through the 17th century. The tradition remains today with the name of the element mercury, where chemists decided the planetary name was preferable to common names like "quicksilver", and in a few archaic terms such as lunar caustic (silver nitrate) and saturnism (lead poisoning). Alchemical compounds. The following symbols, among others, have been adopted into Unicode. Alchemical processes. The alchemical magnum opus was sometimes expressed as a series of chemical operations. In cases where these numbered twelve, each could be  assigned one of the Zodiac signs as a form of cryptography. The following example can be found in Pernety's "Dictionnaire mytho-hermétique" (1758): Units. Several symbols indicate units of volume, weight, or time. Unicode. The Alchemical Symbols block was added to Unicode in 2010 as part of Unicode 6.0.