alchemy Alchemy (from the Arabic word , ) is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practised in China, India, the Muslim world, and Europe. In its Western form, alchemy is first ...

, 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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

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# #''Webster's Revised Unabridged Dictionary'' (1913) Alchemical substances Sulfates {{chem-hist-stub