from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. See ferrous sulfate.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Ferrous sulfate.

from the GNU version of the Collaborative International Dictionary of English

  • n. Green vitriol, or sulphate of iron; a green crystalline substance, of an astringent taste, used in making ink, in dyeing black, as a tonic in medicine, etc. It is made on a large scale by the oxidation of iron pyrites. Called also ferrous sulphate.

from The Century Dictionary and Cyclopedia

  • n. Green vitriol, the sulphate of iron, or ferrous sulphate, FeSO4.7H2O, a salt of a peculiar astringent taste and of various colors, green, gray, yellowish, or whitish, but more usually green.


from The American Heritage® Dictionary of the English Language, 4th Edition

Middle English coperose, a metallic sulfate, from Old French, from Medieval Latin cuperōsa, probably short for *aqua cuprōsa, copper water, from Late Latin cuprum, copper; see copper1.



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  • "De Saussure reckoned that 'more grain is consumed in England for making beer than for making bread', much of it clarified with isinglass or adulterated with dangerous copperas (ferrous sulphate) to make its head froth 'like a cauliflower'."

    --Kate Colquhoun, Taste: The Story of Britain Through Its Cooking (NY: Bloomsbury, 2007), 222

    See also usage/historical note in comment on adulteration.

    January 18, 2017

  • as in bronzed-blue-soothe-sooth-to add lustration

    March 30, 2012

  • "To prepare the fastest blue, for example, you would need an English vat containing 'five times one hundred and twelve pounds of the best woad, five pounds of umbro madder, one peck of cornell and bran, the refuse of wheat, four pounds of copperas, and a quarter of a peck of dry slacked lime.'"

    Mauve by Simon Garfield (quoting William Partridge), p 42 of the Norton paperback edition

    March 30, 2012

  • "A mixture—three pounds copperas, one pint of carbolic acid, one bucket of water—ran through the alleyways and cesspools for cleansing."

    —Molly Caldwell Crosby, The American Plague (New York: Berkeley Books, 2006), 57

    October 5, 2008