Albertus Magnus

Arsenic reached medieval alchemists not as a metal but as two brightly colored minerals, orpiment, a golden-yellow arsenic trisulfide whose Latin name auripigmentum means gold pigment, and realgar, a scarlet arsenic sulfide. Both had been mined and ground for pigment across the ancient and medieval world for centuries before anyone isolated the element itself, and both are seriously poisonous, which did not stop their extensive practical use.

The isolation of elemental arsenic from these ores is credited to Albertus Magnus, working around 1250, by heating orpiment together with soap, a preparation earlier Arabic alchemical writers had likely anticipated in some form though Albertus's account is the one that entered the Latin European tradition and carried his name forward. The achievement mattered beyond arsenic itself: orpiment's gold-like color had long made it a natural candidate for containing some fraction of gold's own essence in the alchemical scheme, and arsenic compounds genuinely do whiten copper into an alloy resembling silver, a visible transformation that helped keep the broader project of transmutation credible to practitioners watching it happen.

Arsenic never fit neatly into the alchemical system built around the seven classical planets and their metals; like antimony, bismuth and zinc, it was worked with constantly but never assigned a planetary correspondence of its own. Albertus's isolation of it stands, in the history of chemistry, as one of the few genuinely traceable "firsts" to survive a period whose chemical claims are mostly anonymous or legendary, credited to a specific friar at a specific and unusually well-documented moment in the thirteenth century.

Albertus Magnus taught at Paris and later at Cologne, and among his students at Paris was a young Dominican named Thomas Aquinas, whose Summa Theologiae and broader synthesis of Aristotelian philosophy with Christian theology built on groundwork Albertus had laid in his own vast commentaries on Aristotle. Albertus was, by the range of his own writing, exactly the kind of scholar who could lay that groundwork: alongside theology and logic he wrote systematically on botany, zoology, mineralogy and natural philosophy, treating the created world as an object of patient, empirical study rather than only theological allegory. He served briefly as bishop of Regensburg before returning to teaching, and was canonized by Pope Pius XI in 1931; a decade later, in 1941, Pope Pius XII declared him patron saint of natural scientists.

That genuine scholarly range also made him an irresistible name for others to borrow. From at least the fourteenth century onward, a body of pseudonymous alchemical and magical texts circulated under his name, most persistently a popular compendium of herbal, animal and mineral "secrets" known in English as the Book of Secrets, offering recipes and occult properties with no real connection to Albertus's own careful, source-citing scholastic method. Modern scholarship does not accept the Book of Secrets or its companion works as genuinely his; they belong to the long practice of attaching a revered scholar's name to material meant to borrow his authority, the same practice that produced pseudonymous works under Aristotle's and Hermes Trismegistus's names. Albertus's own authenticated writings, not the grimoire tradition that grew up around his reputation afterward, are what earned him the title Doctor Universalis in his own lifetime.