* Left: Cover the
bottom of your smallest vial with crystals of
red cobalt
chloride.
* Close this vial by a stopper
which contains a tubing connected to
a stopper of
a second vial.
(The stopper
of the second vial contains an injection needle to prevent a pressure).
* Carefully heat the crystals
until there is no more change.
* Right: A colourless
liquid leaving the red crystals is collected in the right vial.
The red cobalt chloride changes its colour
to blue.
Explanation:
Red
cobalt chloride is not only made by cobalt particles and by chloride
particles.
Its crystals also contain
bonded water molecules. These are known as
water
of crystallisation.
Blue
cobalt chloride is free of water of crystallisation.