h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

http://www.bbc.co.uk/dna/h2g2/brunel/A745715#back4


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just read this entry and whanted to know

why does quenching iron in vinegar make it un-useable

When I first saw this I was a bit stumped as to why. Vinegar is essentially a weak solution of acetic acid in water (with other stuff from the plant from whence it came) and I can't imagine why that this would be any different to water in the quenching of a cast or beaten metal.

So I looked here http://www.metrum.org/measures/castiron.htm (after a google)

and this paragraph

A metal which is quenched by dipping into vinegar certainly is not wrought iron; it must be cast iron or steel. The quenching in vinegar, instead of water, is mentioned in the Pirotechnia of Vannoccio Biringucci (1480-1539 A.D.); ancient metallurgists ascribed great importance to the nature of the quenching medium, and many of their notions, such as the preference for the water of particular streams, may have been superstitions, but vinegar may actually be a better wetting agent than water, as would be a saline solution. I concluded that the metal described by Ploutarchos was cast iron. A number of ancient sources mention the preservation of cast iron in temples as particularly valuable or marvelous. According to Pausanias (III, 12, 10) the edifice called Skias in Sparta was built by Theodoros of Samos (a sort of Leonardo da Vinci of the Greeks—architect, sculptor, inventor), “who first found the way to pour iron and to mold statues with it.”

Suggest that it isn't and so the statement you are interested in may originate in superstition.

Anyway. The whole of that webpage is quite interesting and worth a read