A furnace or oven used by alchemists that maintains constant, even heat for long chemical processes and distillations.
From Arabic 'al-tannur' (the oven), borrowed into Medieval Latin and then European languages. Alchemists adopted this term for their specialized heating equipment used in transmutation experiments.
Medieval alchemists essentially invented the first laboratory hot plates—the athanor was their secret weapon for achieving the precise temperatures needed, and some designs were so efficient they could run for weeks without adjustment!
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