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. The term was also applied to red vitriol (a native sulfate of cobalt), and to green vitriol (ferrous sulfate).

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

References

1.  This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain.
2. Webster's Revised Unabridged Dictionary (1913)