In about 300 A.D., Zosimos provided one of the first definitions of alchemy:
Alchemy (330) the study of the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and bonding the spirits within bodies.
He wrote the oldest known books on alchemy, of which only quotations in the original Greek language or translations into Syriac or Arabic are known. He is one of about 40 authors represented in a compendium of alchemical writings that was probably put together in Byzantium (Constantinople) in the 7th or 8th century AD and that exists in manuscripts in Venice and Paris. Stephen of Alexandria is another.
Arabic translations of texts by Zosimos were discovered in 1995 in a copy of the book Keys of Mercy and Secrets of Wisdom by Ibn Al-Hassan Ibn Ali Al-Tughra'i', a Persian alchemist. Unfortunately, the translations were incomplete and seemingly non-verbatim.
The famous index of Arabic books, Kitab al-Fihrist by Ibn Al-Nadim, mentions earlier translations of four books by Zosimos, however due to inconsistency in transliteration, these texts were attributed to names "Thosimos", "Dosimos" and "Rimos"; also it is possible that two of them are translations of the same book.
In general, his understanding of alchemy reflects the influence of Hermetic and Sethian-Gnostic spiritualities. The external processes of metallic transmutation the transformations of lead and copper into silver and gold--mirror an inner purification and redemption.
The alchemical vessel is imagined as a baptismal font, and the tincturing vapours of mercury and sulphur are likened to the purifying waters of baptism, which perfect and redeem the Gnostic initiate. Here Zosimos draws on the Hermetic image of the 'krater' or mixing bowl, a symbol of the divine mind in which the Hermetic initiate was 'baptised' and purified in the course of a visionary ascent through the heavens and into the transcendent realms. Similar ideas of a spiritual baptism in the 'waters' of the transcendent Pleroma are characteristic of the Sethian-Gnostic texts unearthed at Nag Hammadi. This image of the alchemical vessel as baptismal font is central to his so-called 'Visions', discussed below.
Zosimos shows what had become of alchemy after Bolos of Mende. His theory is luxuriant in imagery, beginning with a discussion of "the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and binding the spirits within bodies" and continuing in the same vein. The "base" metals are to be "ennobled" (to gold) by killing and resurrecting them, but his practice is full of distillation and sublimation, and he is obsessed with "spirits." Theory and practice are joined in the concept that success depends upon the production of a series of colours, usually black, white, yellow, and purple, and that the colors are to be obtained through Theion hydor (divine or sulfur water--it could mean either).
Zosimos credits these innovations mainly to Maria (sometimes called "the Jewess"), who invented the apparatus, and to Agathodaimon, probably a pseudonym. Neither is represented (beyond Zosimos' references) in the Venice-Paris manuscript, but a tract attributed to Agathodaimon, published in 1953, shows him to be preoccupied with the colour sequence and complicating it by using arsenic instead of sulfur. Thus, the color-producing potentialities of chemistry were considerable by the time of Zosimos.
Zosimos also shows that alchemical theory came to focus on the idea that there exists a substance that can bring about the desired transformation instantly, magically, or, as a modern chemist might say, catalytically. He called it "the tincture," and had several. It was also sometimes called "the powder" (xerion), which was to pass through Arabic into Latin as elixir and finally (signifying its inorganic nature) as the "philosopher's stone," "a stone which is not a stone," as the alchemists were wont to say.
It was sometimes called a medicine for the rectification of "base" or "sick" metals, and from this it was a short step to view it as a drug for the rectification of human maladies. Zosimos notes the possibility, in passing. When the objective of alchemy became human salvation, the material constitution of the elixir became less important than the incantations that accompanied its production. Synesius, the last author in the Venice-Paris manuscript, already defined alchemy as a mental operation, independent of the science of matter.
Thus, Greek alchemy came to resemble, in both theory and practice, that of China and India. But its objectives included gold making; thus it remained fundamentally different.