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I’ve been experimenting with producing Iron Acetates and I’ve run into a snag. Here’s my process so far:

I started by adding white vinegar and ~50% Hydrogen Peroxide to a reaction vessel with steel wool sponges and allowing it to react for a month. After that I ran the solution through a filter multiple times until it was fairly clear to remove most of the unreacted solids. After that I tested an aliquot of the fluid by placing some leather in it to see if the leather turned black. It did quite quickly. After that I placed it in a boiling flask and heated it with a flame directly (because I don’t have a big enough beaker or other apparatus to indirectly heat it) and it turned orange. I’m guessing this happened because the elevated temperature allowed it to react with atmospheric oxygen. I continued heating till the solvent was gone leaving a red-brown-black solid on the side of the boiling flask.

Image of flask with undissolved solid

I want to dissolve the solid so I added ~100mL of ~50% Ethanol (Smirnoff blue label vodka) to the flask to dissolve it and left it overnight, but it’s barely dissolved at all. I thought about heating it to create pure ethanol vapor which would do the trick but I don’t have a condenser to condense the ethanol again. Is there a better way of dissolving it?

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  • $\begingroup$ I gather the acetate should dissolve in ethanol? The solid precipitate is surely iron oxide. $\endgroup$
    – Karl
    Apr 30, 2020 at 18:23
  • $\begingroup$ Possibly, but the acetate is supposed to be able to crystallize so presumably the ethanol just isn’t pure enough to break apart the bonds between the molecules very quickly in order to dissolve them. At least at low temperatures $\endgroup$
    – Delaney Fitzpatrick
    Apr 30, 2020 at 21:56
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    $\begingroup$ This is not acetate, this is rust. $\endgroup$
    – AChem
    May 1, 2020 at 4:03
  • $\begingroup$ Try dissolving it with vinegar. $\endgroup$
    – Nilay Ghosh
    May 1, 2020 at 4:26
  • $\begingroup$ Also common rust removal chemicals contain nitric acid. $\endgroup$
    – Nilay Ghosh
    May 1, 2020 at 4:28

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This is all rust which has precipitated on the walls and it is very hard to remove it. You might have to use oxalic acid to remove rust stains on glass. Oxalic acid plays a dual role, it dissolves the rust like an acid, but it also complexes the iron, which prevents further hydrolysis and re-settling.

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    $\begingroup$ Citric acid also works. $\endgroup$
    – Nilay Ghosh
    May 1, 2020 at 4:26
  • $\begingroup$ Ughh I hate that this is right. You mentioned hydrolysis and I checked and ya, that’s what happened. The iron acetate broke down when the vinegar solution was heated causing the iron acetate to turn into iron oxide. That explains the rather sudden change to orange $\endgroup$
    – Delaney Fitzpatrick
    May 1, 2020 at 7:01
  • $\begingroup$ Time to post the follow up question I guess $\endgroup$
    – Delaney Fitzpatrick
    May 1, 2020 at 7:02
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Your precipitate is very likely iron oxides. First make sure you get the remains of the hydrogen peroxide out completely (e.g. by flushing several times with a little distilled water), then use an acid to dissolve the oxide. Possibly acetic acid (vinegar) or citric acid and a little heating will do the job. If not, try 20% sulphuric acid or 10% hydrochloric acid.

BTW reacting possible organic impurities on steel wool etc. with rather concentrated hydrogen peroxide might end up in peroxide formation and serious explosions, especially if one is heating the setup. Something I'd never do in my own lab without lots of safety precautions (a setup as small as possible, fume hood, perspex shield, etc.) and definitely not in my kitchen. Having glass shards picked out of one's face and eyes is no fun.

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  • $\begingroup$ Thanks for the reply! I tried adding a citric acid solution to the flask and heating till just below boiling and the solution turned a dark orange color and some of the residue looked like it started to dissolve. However, adding leather to that solution has yet to change its color so I assume you were right about the residue being at least partly iron oxide, but there should still be some iron acetate left which has yet to dissolve. Could the acetate have denatured or something? $\endgroup$
    – Delaney Fitzpatrick
    Apr 30, 2020 at 21:51

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