Copper sulfate dehydration

Blue crystals turn white at heating and turn blue again after adding water.

Scientific name: Demonstration of the dehydration of hydrated copper (II) sulfate.


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Thermal Decomposition of Copper(II) Sulfate Pentahydrate

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Reaction formula

CuSO4*5H2O → CuSO4 + 5H2O

Step-by-step instruction

  1. Put a few grams of copper sulfate pentahydrate into a test-tube. Secure obliquely this test-tube with a clamp.
  2. Close the test-tube with a stopper with a delivery tube. put The end of the delivery tube in the second test-tube. The second test-tube should be placed in a cold water bath (beaker filled with cold water).
  3. Heat the test-tube with a burner. Move the flame time-to-time to heat the whole test-tube and avoid condensation of the water vapours.
  4. Copper sulfate turns from blue to white. Water from the hydrate collects in the second test-tube.
  5. After the whole copper sulfate sample becomes white, stop heating. Slowly add collected water to the obtained anhydrous copper sulfate, it turns blue again.

Scientific background

Copper sulfate pentahydrate CuSO45H2O is a blue colored substance. When heated it turns to pale blue copper trihydrate CuSO43H2O, and then to white copper monohydrate CuSO4*H2O. After the heating is over 250 °C all molecules of water are removed. After the addition of water, copper sulfate hydrates are formed again.


Published on 22 October 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst