Tuesday, December 06, 2011

Lab Notes: Iron Oxides

For fun, I had this idea: the classic grade-school experiment: making rust. Good ol' iron oxide. So, I grabbed a small row of staples, added some salt, and dropped them in the water.... and waited.

I'm not the most patient person in the world, so I grew tired of how long it was taking to turn steel into rust. Thinking to myself, "Hydrogen peroxide is an oxidizer, therefore, hydrogen peroxide should make the rust faster", and it did. What I ended up with was iron hydroxide, no iron oxide, but with heat it dehydrates, which yielded the black iron oxide, magnetite. Not surprisingly, it's magnetic and quite fun to play with, but it wasn't what I was after, I wanted the deeply red Iron (III) Oxide. When rust forms, it's a mix of oxides and hydroxides. I was hoping to separate the two by somehow driving one into solution, while leaving the other alone. The idea occurred to me by way of a mistake. I had a vial of what was left over after attempting to get a purer form of acetic acid through heat distillation, instead of grabbing the empty vial, I grabbed that one instead, pouring  the magnetic iron oxide into that instead of an empty vial. I noticed that the brown portion was gone, leaving behind only the black. I also noticed that the solution took on a very strong orange coloration. So, I set out to attempt this. Reacted more of the oxide with vinegar (acetic acid), and filtered. To my surprise what came out was a stunningly bright orange solution. What I'm not sure of right now is if it is iron acetate, or iron oxide dissolved in acetic acid. I'm in the process of evaporating the liquid from the solution, and I will see what I get when I rinse the dry product with water.

On another note about the oxidation with hydrogen peroxide, it seems to go much faster with the introduction of sodium chloride (table salt), I don't know the mechanism behind this, but it was very interesting to observe.

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