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Next time you set up a reflux reaction in your lab or kitchen, spare a thought for the equellum: the original recirculating reactor.
Though largely forgotten today, the equellum played a vital role in the transition from medieval alchemy to modern chemistry. An equellum is a small, often crucible-like vessel with a distinctive feature: a built-in, inverted funnel or a porous septum inside its neck. Its name derives from the Latin equus (horse), possibly alluding to the “bridle” or restraint the device placed on escaping vapors.
When you picture an ancient laboratory, you likely imagine glass beakers, copper stills, and bubbling flasks. But for centuries, one of the most critical tools on the workbench was a small, unassuming device called an (plural: Equella ).
