Reversible hydrate formation of copper(II)-sulfate

Chemicals needed

copper(II)-sulfate, pentahydrate GSGESUND.gif (476 Byte) Xn  GSUMWELT.gif (758 Byte)  N    R 22-36/38-50/53    S (2)-26-36/37/39-60-61

Equipment necessary

porcelain crucible (alternatively heat-resistant test tube)
crucible tongs or test tube holder
burner (preferably gas-)

Test procedure



Many (mineral-)salts form rather instable hydrates, out of which the water of crystallization can be driven out by heating. In the case of copper(II) sulfate this is, due to the different coloring of the hydrates, especially beautiful to observe.


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copper(II) sulfate, pentahydrate before experiment

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copper(II) sulfate after dehydration

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copper(II) sulfate after rehydration


a classical experiment, recreated from a school experiment