Chalcanthum

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).[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. ^ a b 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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