What Is the Mysterious Liquid Produced When Steel Is Mixed with Vinegar?

[JGM_14]

I mixed steel with vinegar and what resulted was a deep red liquid and some orange particles at the bottom. What is this liquid? Is it Fe2O3? If not then what, and is Fe2O3 magnetic?

 

[mrjeffy321]

Was the steel totally submerged in the liquid, or was it exposed to air too?

Is the red liquid a solution or suspension? Are there just red particles floating around in the liquid which will eventually settle if left undisturned, or is the liquid itself red?

I suspect the Iron in the steel reacted with the acetic acid (vinegar) and formed Iron Acetate. According to my CRC book, "Iron (III) Acetate, Basic" FeOH(C2H3O2)2 is brown/red in solid form (but this is insoluble in water), and according to wikipedia, Iron (II) Acetate forms a light-green tetrahyrate, so these might be contributing to the color of the liquid.
And it is also possible for some Fe2O3 (non-magnetic) to have formed as well, which is also reddish brown, but will not dissolve in solution, it will settle out after a while.

 

[JGM_14]

It was brown after the liquid evaporated off but the liquid was orange then some light orange particles settled to the bottom and the liquid became almost blood red.

 

[mrjeffy321]

How badly do you want to know what the liquid (or rather, what is dissolved in the liquid) is?
You could start precipitating out various compounds to analyze. For example, there is likely some Fe+? (Likely Fe+2) ions in solution, you could add some Sodium Hydroxide and precipitate out Iron Hydroxide. Iron Hydroxide is quite easy to convert to Iron Oxide through heating. Based on its color and magnetic properties you could figure out of it is Fe2O3 or Fe3O4 (or FeO). You could also try to oxidize or reduce whatever is in solution with a strong oxidizing/reducing agent (Potassium Permanganate for example, or Aluminum/Zinc). There are various "games" you can play to try to identify what ions are present in the solution. Of course you would want to perform all these tests separately on smaller samples, to avoid contaminating your stock of mystery liquid.