Description of experiment
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Needed compounds:
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hydrochloric acid : HCl
ferric chloride anhydrous : FeCl3
Class:
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elem=Cl,Fe
Summary:
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Ferric chloride anhydrous easily melts and when it melts, it also nearly boils
and a dark yellow/brown vapor is formed, which condenses to beautiful crystals
in cooler areas.
A small part of the ferric chloride reacts either with oxygen from the air, or
with water vapor in the air. Insoluble oxide-species are formed.
Description:
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Put a spatula full of anhydrous ferric chloride in a perfectly dry test tube
and heat the test tube in the flame of a propane torch: Quickly the solid melts
and a yellow/brown vapor is released. On stronger heating, the material is
refluxing in the test tube and at the top of the vapor column there is a
beautiful 'cloud' of glittering crystals. Below the cloud there is a dark
brown/yellow vapor.
Allow the test tube to cool down: The vapor condenses and many small glittering
crystals settle on the glass.
After cooling down add some water: Most of the solid material dissolves, but
the solution remains very turbid and somewhat reddish/brown. Apparently quite
some ferric chloride is converted to ferric oxide or some basic chloride. Maybe
this is due to exchange of chlorine and oxygen, or watervapor from the air has
reacted with the ferric chloride, giving hydrogen chloride and ferric oxide.
Add some hydrochloric acid: The liquid remains turbid.
Heat the liquid: Slowly the liquid turns clear and deep yellow. The
hydrochloric acid dissolves the ferric oxide and the liquid becomes clear.