Chalcanthum

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In alchemy, chalcanthum, also called chalcanth or calcanthum, was a term used for the compound blue vitriol (CuSO4), and the ink made from it. [1] The term was also applied to green vitriol (ferrous sulfate). [2]

Some maintained calcanthum to be the same thing as colcothar, while others believed it was simply vitriol (sulfuric acid). [3]

The term "vitriol rubified" (Latin: reddened vitriol) refers to the reddish iron oxide residue (colcothar) left after heating green vitriol, and should not be confused with "red vitriol," a distinct mineral (native cobalt sulfate).[ citation needed ] [3]

References

  1. ↑ van Helmont, Jean Baptiste (1664). "The Author offers a dainty Dish to young Beginners". Van Helmont's Works. London: Lodowick Lloyd. Retrieved 2025-12-11– via University of Michigan Library (EEBO). nature hath produced a certain acide or tart Mineral salt, which the Greeks do name Calcanthum; and the Latines (by an unfit name) Atramentum Sutorium, or shooemakers ink. But the Chymists call it Vitriol
  2. ↑ "Copperas". Webster's Revised Unabridged Dictionary . 1913. Green vitriol, or sulphate of iron; a green crystalline substance, of an astringent taste
  3. 1 2 Chambers, Ephraim (1728). "Chalcanthum". Cyclopædia, or an Universal Dictionary of Arts and Sciences . Vol. 1. London. p. n360. Chalcanthum, Χαλκανθες, the same with vitriol. See Vitriol. Some have also used Chalcanthum corruptly for colcothar, or vitriol rubified.
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