reidy2015 - 5-5-2015 at 21:53
IrC - 5-5-2015 at 23:08
I'm no chemist but my guess would be water.
Volanschemia - 5-5-2015 at 23:37
Iron(III) Chloride usually exists as the hexahydrate, being Iron(III) Chloride Hexahydrate (FeCl3•6H2O)
Anhydrous means that the molecule does not have any hydration, so anyhrous Iron(III) Chloride has no water integrated into its crystal structure.
reidy2015 - 6-5-2015 at 01:15
Thanks 
aga - 15-5-2015 at 00:19
AFAIK Ferric Chloride cannot be brought to an anhydrous state once it has come into contact with water.
It simply will never let go of all the water, so boiling it to dryness doesn't work.
The only way i know to get true Anhydrous FeCl3 is by direct union of the elements (pass chlorine gas over/through iron filings).
The '111' should be written as (III) which shows the oxidation state of the iron in the compound (3 in this case) e.g.
Iron (III) Chloride = FeCl3 = Ferric Chloride, Fe being 3+
Iron(II) Chloride = FeCl2 = Ferrous Chloride, Fe being 2+
[Edited on 15-5-2015 by aga]
j_sum1 - 15-5-2015 at 02:19
My experience of FeCl3 is that it is hard to dry. I gave up.