July 21, 2024, 06:24:26 PM
Forum Rules: Read This Before Posting


Topic: Color of Iron (II) and Iron (III) species  (Read 6567 times)

0 Members and 1 Guest are viewing this topic.

Offline Grundalizer

  • Full Member
  • ****
  • Posts: 257
  • Mole Snacks: +19/-31
Color of Iron (II) and Iron (III) species
« on: July 12, 2011, 07:24:17 PM »
I made some copper acetate solution, then I placed some zinc coated screws/nails in the solution and the copper was reduced and came out of solution--into the solution goes Zinc++ as well as some Iron, because I let it sit for a few days so I saw some rust developing.

Anyway, I filtered off the slurry that was some iron oxides/hydroxides/who knows what and took the dark brown liquid leftover.

That looked EXACTLY like Iron III acetate

http://en.wikipedia.org/wiki/Iron(III)_acetate

So, perfect, I know what it is.

I throw some Sodium Metabisulfite  into the mixture, and let it sit, the brown color completely dissapears and turns clear with a little excess Sodium meta on the bottom, and the tiniest 5mm thick layer of brown colored stuff, probably iron acetate.

My question is, Iron (II) and Iron (III) are known to have colors, but what made this clear?  Were they all reduced to Iron (I)??  There was no metal that precipitated out so Iron is still in solution, I just don't know as what.

Thanks

Offline DevaDevil

  • Chemist
  • Full Member
  • *
  • Posts: 690
  • Mole Snacks: +55/-9
  • Gender: Male
  • postdoc at ANL
Re: Color of Iron (II) and Iron (III) species
« Reply #1 on: July 13, 2011, 10:18:15 AM »
I do not believe iron (I) can exist as is in solution. (only exists in complexes)
A dilute solution of iron (II) sulfate would seem pale green, maybe confused with colorless?

metabisulfite is indeed a weak reducing agent (it oxidizes itself), so some reduction of iron (III) to iron (II) is expected.

Offline Grundalizer

  • Full Member
  • ****
  • Posts: 257
  • Mole Snacks: +19/-31
Re: Color of Iron (II) and Iron (III) species
« Reply #2 on: July 13, 2011, 07:10:16 PM »
Perhaps...I was working with fenton's reagents recently and was using a lot of ferrous sulfate and ferric sulfate salt, and even though the crystals are a really really pale green, this solution definitely looked crystal clear.  Although, if I recall the solution was rather clear anyway when I was using pure ferrous sulfate.  I just could have sworn I read somewhere recently that when both Iron II and Iron III salts are together, they are colorless, even though separate they are pale green and reddish orange respectively.

If I can get two samples of the pure salts again I'll mix them together and see what color they turn.  Thanks for the response.

Sponsored Links