ummmmm......
"Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3. "
could also be written as "iron tri-chloride"
it just so happens that out of iron's two stable valence states of 2 or 3, that chlorine likes 3 when the temperature is below 300C
interesting side note:
i used to have a cat that for some reason would not stay away from my etchant tank. i had to keep the cat locked out of the room where i kept it, because this cat would do anything to get to it. more than a few times i would find the cat had somehow gotten in and was lapping the stuff up like milk, and i would chase him away, lock the door and spend an hour or so watching the cat for anu signs of discomfort etc... which never happened. mind you the etchant the cat was drinking was used etchant, and so was a mixture of iron chloride and copper chloride, and was MORE poisonous as a result, but this cat would fight to get to the stuff, and never suffered any ill effects...... i guess cats can digest just about anything?????? i don't know, but that's always puzzled me........