Copper (II) sulfate, also known as cupric sulfate or copper sulphate, is the chemical compound with the chemical formula CuSO4. This salt exists as a series of compounds that differ in their degree of hydration. The anhydrous form is a pale green or grey-white powder, whereas the pentahydrate (CuSO4·5H2O), the most commonly encountered salt, is bright blue.
|Copper Sulphate Crystals|
Copper sulphate is normally produced industrially by treating copper metal with hot concentrated sulphuric acid. Laboratories generally purchase their own – eg here.
At 650 °C (1,202 °F), copper (II) sulphate decomposes into copper (II) oxide (CuO) and sulphur trioxide (SO3). Its blue colour is due to water of hydration. When heated in an open flame the crystals are dehydrated and turn greyish-white.
Several chemical tests utilize copper sulphate. It is used in Fehling’s solution and Benedict’s solution to test for reducing sugars, which reduce the soluble blue copper(II) sulphate to insoluble red copper(I) oxide. Copper(II) sulphate is also used in the Biuret reagent to test for proteins.
Copper sulphate is a commonly included chemical in children’s chemistry sets and is often used to grow crystals as can be seen here.
The chemical is also used in flame tests – again which can be seen here.
In 2008, the artist Roger Hiorns filled an abandoned waterproofed council flat in London with 75,000 litres of copper sulphate solution. The solution was left to crystallize for several weeks before the flat was drained, leaving crystal-covered walls, floors and ceilings. The work is titled Seizure.
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