An alchemist was an early student of the science of chemistry. According to one theory the the word "alchemy" is derived from Khem, the ancient name for Egypt. That country was the source of a great deal of the pioneer work in the various sciences.
Much of the early work of the alchemists is frowned on by today's scientists because it was bound up with experiments to find the "elixir of life" and the "philosopher's stone" which would turn all base metals into gold. The alchemists also studied magic and astrology.
However, we have to thank the alchemists for such words as "hermetically sealed", alcohol, and alkali, and for the discoveries of sulphuric, nitric, and hydrochloric acids, and of metals such as antimony, bismuth and arsenic.
The "hermetic art" is another name for alchemy. Hermes Trismegistus was the name given by the Greeks to the Egyptian god of alchemy. Thus hermetic sealing is derived from the method of airtight sealing used by alchemists in their experiments.
The alchemists also associated the planets with certain metals and used the astrological symbol as a shorthand sign for the metal. The sun stood for gold, the moon for silver, Venus for Copper, Mars for iron, Jupiter for tin and Saturn for Lead.