Anhydrous ferric chloride is prepared by:
Heating metallic iron in a stream of dry chlorine gas.
In order to prepare, Anhydrous iron(III) chloride, we start with iron filings and heat it is a stream of dry chlorine gas.
The reaction for this process is as given below.
2 Fe(s) + 3 Cl2(g) → 2 FeCl3(s)