What kind of alchemy is attested by tenth-century Coptic manuscripts?

This article places the four extant Coptic alchemical manuscripts within the context of the tradition of Coptic scientific texts. One of the manuscripts is a palimpsest written over an erased literary text, apparently in the tenth century. The other three all come from the same library, and are unlikely to be later than the mid-tenth century. Their vocabulary, form and contents are analysed, and the wonderful "machine of the sages" is introduced. It is shown that the texts most likely depend on Arabic alchemical texts, because of the number of Arabic words left in transliteration, and their style. In this case, they are the earliest witnesses to Arabic alchemy.