Sciencemadness Discussion Board

Drying Ferrous Chloride Crystals

CHRIS25 - 30-11-2012 at 03:27

I have made Ferrous chloride crystals but am not sure if they will oxidize if left out in the air to dry. I read somewhere that (a few days ago) that they can not be dried in a dessicator bagwith one of the conventional drying agents since they need to stabilize their environment with moisture, laying a very thin oxide layer over the crystals, to prevent the oxidation to ferric chloride. Is this true please?

woelen - 30-11-2012 at 04:05

FeCl2.4H2O is very air sensitive. It at once is oxidized, especially when wet. I once made crystals of this compound and they looked beautifully mint green. On exposure to air the crystals immediately turned grass green, due to oxidation and formation of ferric ions.

CHRIS25 - 30-11-2012 at 04:45

Quote: Originally posted by woelen  
FeCl2.4H2O is very air sensitive. It at once is oxidized, especially when wet. I once made crystals of this compound and they looked beautifully mint green. On exposure to air the crystals immediately turned grass green, due to oxidation and formation of ferric ions.


Ok, that you mention mint green to grass green is a giveaway. In that case my crystals are oxidized ferrous chloride, but not quite ferric? I know this makes no sense but ferric chloride is always ranging from yellow to yellow brown to very dark brown green; so is this more of a transition stage, could I ensure ferrous chloride crystals by adding a little water, add a little tiny piece of fine Iron, let it react until the ferrous stage is assured - filter and seal immediately? By the way, always have trouble accessing your web page via any links that I find, always get taken to what I presume to be the host server from where I can not navigate to anything of yours.

[Edited on 30-11-2012 by CHRIS25]

tetrahedron - 30-11-2012 at 04:51

FeCl2 oxidizes easily. this is the initial step in recovering HCl from pickling baths:
Quote:
12 FeCl2 + 3 O2 -> 8 FeCl3 + 2 Fe2O3

see also my post in this thread.

CHRIS25 - 30-11-2012 at 05:03

Quote: Originally posted by tetrahedron  
FeCl2 oxidizes easily. this is the initial step in recovering HCl from pickling baths:
Quote:
12 FeCl2 + 3 O2 -> 8 FeCl3 + 2 Fe2O3

see also my post in this thread.

Yes I know how unstable ferrous chloride is. But my main goal is to ensure that I produce ferric chloride crystals. I boiled off as much liquid as I could (HCl and water), filtered, though the absence of any significant carbon in the steel wool was a surprise), allowed to dry for two days, they are still half way between Woelen's clarification of bright lime green to dark grass green, indicating the ongoing oxidation, so my wish was to preserve the crystals in a tetrahydrate state and store. Question is more about drying them properly either in an airtight container without a drying agent(since I did read somewhere that using adrying agent such as NaOH was not good - can not remember where though), or simply that this can not be done really in a home set-up. I am unable to find any references about this procedure.

[Edited on 30-11-2012 by CHRIS25]