aludel

An aludel is a pear-shaped earthenware vessel, open at both ends, designed to be fitted onto another aludel of identical shape, forming a column in which substances could be heated at the bottom and collected as vapor at the top. Medieval alchemists used aludels primarily for sublimation, the process by which a solid converts directly to gas and then condenses as a purified solid. The word entered English in the 16th century from Spanish aludel, which had borrowed it from Arabic al-uthāl during the centuries when Toledo was the great translation hub between Arabic and Latin learning. The Arabic root may relate to a word for pipes or tubes, though the precise etymology within Arabic is not settled.

The apparatus is described in the writings of Jabir ibn Hayyan, the 8th-9th century Arab alchemist who worked in Kufa and whose texts formed the foundation of Islamic alchemy. Jabir's instructions for subliming arsenic, sulfur, and mercury mention clay vessels fitted together in a column, the ancestor of the named apparatus. When Gerard of Cremona and others translated Arabic alchemical texts into Latin in 12th-century Toledo, al-uthāl crossed the language barrier largely intact, its Arabic article fused to the noun as often happened in those translations. By the 13th century, European alchemists were ordering aludels from potters who already knew the shape by name.

The apparatus appears in Chaucer's Canon's Yeoman's Tale of around 1390, in a list of alchemical equipment the Yeoman sarcastically enumerates for the pilgrims. Chaucer lists aludels alongside cucurbits, retorts, and alembics, suggesting the word was already familiar to an educated English audience by the late 14th century. The aludel's design is elegant in its simplicity: no moving parts, no mechanical complexity, just gravity and heat and clay. Robert Boyle's 1680 New Experiments and Observations Touching Cold still uses the term when describing the sublimation of camphor.

Chemistry eventually replaced alchemy, and laboratory glassware replaced clay earthenware, but the word aludel persisted in English scientific dictionaries well into the 19th century. Samuel Johnson defined it in his 1755 Dictionary simply as a subliming pot. By the time alchemy had been entirely discredited, the aludel had been quietly replaced by glass flasks and condensers, but its Arabic name stayed in the record. The word now turns up almost exclusively in historical and alchemical texts, a fossil from the age when Toledo's translators gave Europe a vocabulary for the laboratory.