Pseudo-Geber

Pseudo-Geber (or "Latin pseudo-Geber") is the presumed author or group of authors responsible for a corpus of pseudepigraphic alchemical writings dating to the late 13th and early 14th centuries. These writings were falsely attributed to Jabir ibn Hayyan (died c. 806–816, Latinized as Geber), an early alchemist of the Islamic Golden Age.

The most important work of the Latin pseudo-Geber corpus is the Summa perfectionis magisterii ("The Height of the Perfection of Mastery"), which was likely written slightly before 1310. Its actual author has been tentatively identified as Paul of Taranto. The work was influential in the domain of alchemy and metallurgy in late medieval Europe. The work contains experimental demonstrations of the corpuscular nature of matter that were still being used by seventeenth-century chemists such as Daniel Sennert, who in turn influenced Robert Boyle. The work is among the first to describe nitric acid, aqua regia, and aqua fortis.

The existence of Jabir ibn Hayyan as a historical figure is itself in question, and most of the numerous Arabic works attributed to him are, themselves, pseudepigrapha dating to c. 850–950. It is common practice among historians of alchemy to refer to the earlier body of Islamic alchemy texts as the Corpus Jabirianum or Jabirian Corpus, and to the later, 13th to 14th century Latin corpus as pseudo-Geber or Latin pseudo-Geber, a term introduced by Marcellin Berthelot. The "pseudo-Geber problem" is the question of a possible relation between the two corpora. This question has long been controversially discussed. It is now mostly thought that at least parts of the Latin pseudo-Geber works are based on earlier Islamic authors such as Abu Bakr al-Razi (c. 865–925).

The following set of books is called the "pseudo-Geber Corpus" (or the "Latin Geber Corpus"). The works were first edited in the 16th century, but had been in circulation in manuscript form for roughly 200 years beforehand. The stated author is Geber or Geber Arabs (Geber the Arab), and it is stated in some copies that the translator is Rodogerus Hispalensis (Roger of Hispania). The works attributed to Geber include:

Being the clearest expression of alchemical theory and laboratory directions available until then—in a field where mysticism, secrecy, and obscurity were the usual rule—pseudo-Geber's books were widely read and influential among European alchemists.

The Summa Perfectionis in particular was one of the most widely read alchemy books in western Europe in the late medieval period. Its author assumed that all metals are composed of unified sulfur and mercury corpuscles and gave detailed descriptions of metallic properties in those terms. The use of an elixir for transmuting base metals into gold is explained (see philosopher's stone) and a lengthy defense is given defending alchemy against the charge that transmutation of metals was impossible.

The practical directions for laboratory procedures were so clear that it is obvious the author was familiar with many chemical operations. It contains early recipes for producing mineral acids. It was not equaled in chemistry until the 16th century writings of chemist Vannoccio Biringuccio, mineralogist Georgius Agricola and assayer Lazarus Ercker.

The next three books on the list above are shorter and are, to a substantial degree, condensations of the material in the Summa Perfectionis.