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No. 964:
Maria the Jewess

Today, a brilliant chemical engineer provides grist for the alchemists' mills. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The great chemist Maria the Jewess has been pretty well lost in the blur of ancient history. Most of what we know about her comes from the Egyptian alchemist Zosimos, who wrote in the late days of the Roman empire, 500 years after Maria lived. Among other things, Zosimos talks about her invention of the kerotakis.

Maria invented many types of stills and reflux condensers. The kerotakis device was one in which she could boil mercury or sulfur and use its condensing vapor to heat copper or lead in a pan above. It was a kind of high-temperature double boiler.

Remember how a double boiler works: It has an upper pan where you cook food, nested in a lower pan of boiling water. The food stays at the same temperature as the steam condensing under it -- 100 degrees C. And so the one reference to Maria in the modern world is the French word for a double boiler. They call it a bain-marie -- Maria's bath.

Maria gave us far more than just the double boiler -- significant as that is. She founded an important school of chemistry in the late 3rd century BC. She worked a little after Euclid. She could well have known Archimedes in Alexandria.

Scholars speculate on her origins. She's called The Jewess because Zosimos called her a Sister of Moses. That could well've been no more than a convoluted way of saying she was wise. She could've been a Greek working in Egypt, or even a Syrian.

She studied sulfur compounds. It was Maria who created the process for making silver sulfide -- what artists call niello. That's a matte black compound, often used for metalwork inlays.

Maria wasn't really an alchemist. She was less interested in the philosophy of transmutation than she was in practical chemical processes. The alchemists of a later age used some pretty fanciful and metaphorical language to describe her processes. But that was their rhetoric, not hers.

Maria was closer in her thinking to Egyptian process engineers -- like the Egyptian women who developed the process chemistry for brewing beer. Maria was closer kin to today's chemical engineers than she was to the philosphers of a later age -- who made such heavy use of her stills and her processes.

And the French word bain-marie is the only place we still hear her name today -- that and the French slang term, femme au bain-marie, which means an empty-headed pretty woman, a woman with a double boiler for a head.

Now there is a sorry reminder of how much we've forgotten -- about who Maria the Jewess really was, and all she accomplished.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Multhauf, R.P., the Origins of Chemistry, New York: Franklin Watts, Inc., 1966.

Taylor, F.S., The Alchemists, New York: Arno Press, 1974.

Federmann, R., The Royal Art of Alchemy, (tr. by Richard H. Weber), Philadelphia: Chilton Book Co., 1964.

I am grateful to Kathryn Krause, UH Library, for locating a great deal of good source material on Maria the Jewess.