05:8 · The planet Neptune was first discovered in 1846. had then already been in use for hundred of years in alchemical contexts.
    It sometimes signified mercury and sometimes lime. In the chemistry of the seventeenth and eighteenth centuries was. common sign for quicklime, unslaked lime, according to Diderot's Encyclopedia. The sign was also used to denote calcinare, the process whereby quicklime is made. The calcination process is explained at the sign entry in Group 18.