mangoman667
Harmless
Posts: 37
Registered: 10-10-2014
Member Is Offline
Mood: No Mood
|
|
Precipitate after oxidizing iron
Hi guys,
I'm attempting to make ferric chloride the slow and dirty way. I have been dissolving a piece of iron in an HCl/H2O2 mixture for
quite some time now. When I took 50mL and added peroxide to saturation, I got a beautiful color change from yellow-clear to dark brown. However, it
has now been a day, and there is a bright yellow-orange precipitate at the bottom of the beaker. Can anyone take a gander at what exactly this may be?
It might be worth noting that this also happened with a batch that I made out of ultra fine steel wool.
[Edited on 6-26-2015 by mangoman667]
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
Most likely an oxide/hydroxide of iron. Try adding small incremental amounts of HCl to the solution, with stirring, to see if it redissolves.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Mangoman:
To prepare compounds like that w/o paying much attention to stoichiometry and other 'rules' is a recipe for all kinds of unexpected/hard to explain
phenomena to take place.
Fe(III) needs very low pH values to stay in solution, even lower at high concentrations. Too high pH causes hydoxide/hydroxichloride(s) to
precipitate.
Like WGTR said, extra HCl can often redissolve these.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
in my experience mangoman667, when blogfast25 suggests something, it generally saves a lot of time and heartache if you read it at least twice and
then follow the advice !
[Edited on 26-6-2015 by aga]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by aga  | in my experience mangoman667, when blogfast25 suggests something, it generally saves a lot of time and heartache if you read it at least twice and
then follow the advice !
|
Hmmm... the guy who decided to follow my serving suggestion for 'Rat a l'Orange' begs to differ.
Incidentally, no iron got reduced in mango's workings. Pure HCl solution oxidises Fe(0) to Fe(+2). In the presence of peroxide and depending on its
quantity you end up with Fe(+3) or mixed in with Fe(+2).
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
I guess that when you typed 'droppings' you meant drippings.
Typos can get you into all sorts of trouble.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
No, no, I meant 'Cat a l'Orange', sorry!
|
|
|
mangoman667
Harmless
Posts: 37
Registered: 10-10-2014
Member Is Offline
Mood: No Mood
|
|
Unfortunately, I have no scales, so it is very hard to work with perfect stoichiometry. Also, I had a brain fart, and typed reducing instead of
oxidizing, well spotted 
Anyways, that's quite interesting that the ions have trouble staying in solution at a higher pH. I will now try to redissolve these precipitates by
adding HCl, and I'll report back my findings.
EDIT: The precipitate did dissolve on addition of 12M HCl. I'm going to guess that it would be difficult to determine between the oxide and the
hydroxide.
I also did another trial in which I tried to concentrate the dark brown solution by boiling, to study the insolubility of the Fe(III). After 10 of
40mL evaporated, I noticed the solution has turned somewhat cloudy. It is now cooling and I will post my findings once again.
[Edited on 6-26-2015 by mangoman667]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
FeCl3.6H2O has very high solubility and is rather hard to crystallise for that reason. It's a yellow, mushy, micro-crystalline substance.
[Edited on 26-6-2015 by blogfast25]
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
FeCl3 is a bitch.
Blast/Boil/Scream it to dryness and hope for the best.
If you come up with a working procedure (starting with iron wool and HCl) please post it here and you'll maybe get a Nobel Prize.
If you do really well, maybe a kiss off blogfast (cheek only: the cheek to be appropriately studied and cleansed beforehand)
|
|
|
Molecular Manipulations
Hazard to Others
Posts: 447
Registered: 17-12-2014
Location: The Garden of Eden
Member Is Offline
Mood: High on forbidden fruit
|
|
'Blast' it all you want aga, but you wont get it dry. Anhydrous ferric chloride is made with dry hydrogen chloride gas or chlorine. Like aluminum
chloride, contact with water causes hydration, heating decomposes it/them to the oxide and HCl (g).
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
|
|
|
mangoman667
Harmless
Posts: 37
Registered: 10-10-2014
Member Is Offline
Mood: No Mood
|
|
However it can be crystallized, correct? I'm making it to stock up for etching printed circuit boards, and I can't be bothered to be storing jars of
this stuff forever.
Also, I have realized that this stuff stains glassware, and now I have no idea how to get rid of said stains. Anyone have any ideas?
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
An interesting experiment, for small scale preparation of the anhydrous chloride, would be to place a red hot iron rod into a large vessel containg
dry Cl2 (or containing a chlorine generator) where the vessel has been cooled to collect any vapors produced. In other words, I am saying that Iron
burns in an atmosphere of Cl2. To quote a source (link: http://www.chemguide.co.uk/inorganic/group7/otherreactions.h... ):
"Reactions with iron
With the exception of iodine, iron burns in the halogen vapour to give iron(III) halides. Iodine is less reactive, and only produces iron(II) iodide."
The net reaction with an excess of Chlorine is likely given by:
2 Fe + 3 Cl2 = 2 FeCl3
implying that 22.4 liters of Chlorine produces but 2/3 of a mole of Ferric chloride, but I am unclear to what extent FeCl2 may also be formed on a
shortfall of the Cl2 input (see last cited video below where an intense red color is no longer observed and this source noting the possible creation
of the FeCl2 salt as well http://www.chemeddl.org/alfresco/service/org/chemeddl/video.... ). As such, a more convoluted reaction sequence could be (which introduces an
intermediate FeCl2 formation depending on the relative iron to Cl2 concentrations) for example:
3 Fe + 9/2 Cl2 ==> 3 FeCl3
2 FeCl3 + Fe ==> 3 FeCl2
3 FeCl2 + 3/2 Cl2 ==> 3 FeCl3
---------------
Net: 4 Fe + 6 Cl2 ==> 4 FeCl3
Given there are thermodynamic stability differences between the Ferric and Ferrous chloride, see this reference detailing energy considerations and
claiming that the direct union of Iron and Chlorine to form Ferrous chloride does not occur in accord with the propositon above: https://www.google.com/url?sa=t&source=web&rct=j&...
Here are some related videos: http://m.youtube.com/watch?v=uKqiWqpjlUQ ,
http://m.youtube.com/watch?v=ygLDJKG_QSY and http://m.youtube.com/watch?v=DZnVMW1ZYyA
Other issues, I suspect, are the presence of any water vapor and, my personal drawback, a source of pure iron (perhap a magnet of Fe and C)
commensurate with the level of purity desired (that is, alloy metals present could potentially form their respective chlorides as well).
But, the experiment itself is most likely fast and exciting, but take precautions given the presence of toxic and corrosive fumes.
[Edit] More details on my suggested preparation courtesy of Atomistry.com on FeCl3 to quote:
"Ferric chloride, FeCl3, occurs in nature in the lava of Vesuvius, as the mineral molysite. In the laboratory it is prepared in the anhydrous
condition by passing a rapid current of dry chlorine through a retort over heated iron wire, advantageously cut into pieces some 6 mm. in length. The
ferric chloride volatilises and condenses as beautiful crystals on the upper, cooler portions of the retort.
At the end of the operation the heating is discontinued and the chlorine expelled from the apparatus by a rapid current of carbon dioxide. The salt is
now rapidly transferred to a tube and hermetically sealed."
Link: http://iron.atomistry.com/ferric_chloride.html
As a sidebar, the cited explosive property of Cl2 and H2 in sunlight in the first reference above, does not actually occur in the presence of any O2
(which apparently introduces a termination step into the otherwise explosive chain reaction sequence.)
[Edited on 30-6-2015 by AJKOER]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by mangoman667 | However it can be crystallized, correct? I'm making it to stock up for etching printed circuit boards, and I can't be bothered to be storing jars of
this stuff forever.
Also, I have realized that this stuff stains glassware, and now I have no idea how to get rid of said stains. Anyone have any ideas?
|
Yes. You need a strong acid (HCl) reserve to prevent it from hydrolysing while you simmer it down. Once your solution is almost black, allow to cool
and stand for a few days. If a yellow substance starts crystallising, that's FeCl3.6H2O. If not, gently continue boiling off solvent for some more.
The stains are almost certainly Fe(OH)3 or Fe hydroxychlorides. They should dissolve in strong HCl or 50 % H2SO4.
[Edited on 29-6-2015 by blogfast25]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
