On Alums and Salts, sometimes attributed to the Persian polymath al-Razi, is one of the most influential treatises in the European alchemical tradition. This Arabic alchemical work, produced in twelfth-century al-Andalus, gained wide fame in its Latin translations, and is also represented by a unique and fascinating Hebrew manuscript that includes practical commentary added by its anonymous Jewish compiler. Gabriele Ferrario's new edition presents both the Arabic and the Hebrew texts, each with a full translation into English. Together, the two editions of On Alums and Salts tell the story of the active acquisition of chemical knowledge, of lexical creativity and ingenuity, and of scientific engagement that crossed chronological, linguistic, cultural, and religious boundaries.