What is the chemical name of blue vitriol, and what is it used for in everyday life and in industry?
Blue vitriol is copper(II) sulfate pentahydrate, CuSO4·5 H2O. The compound is called blue vitriol because because it can be prepared by oxidizing copper in hot concentrated sulfuric acid (“oil of vitriol”): Cu(s) + 2 H2SO4(l) + 3 H2O(l) CuSO4·5 H2O(s) + SO2(g) The compound also occurs naturally as the mineral chalcanthite- one of the few soluble sulfate minerals. It is also called “bluestone”, “copper vitriol”, and “flower of copper”. The beautiful blue color arises from water molecules attached directly to the copper(II) ion. The water/copper ion complex absorbs photons of yellow or red light. Absorption of a photon promotes an electron from the water to the copper(II) ion. Since only yellow or red light is absorbed, blue light is transmitted, and the crystals appear blue. If blue crystalline CuSO4·5 H2O is heated strongly, the hydration water is driven off, leaving white powdery CuSO4 (“anhydrous” copper(II) sulfate). The blue will reappear if the anhydrous copper sulfate is exposed
