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April 23 2012 2 23 /04 /April /2012 13:22

I tried to extract pure chromium metal from a stainless steel spoon. It turned out to be much more difficult than I expected.

 

I had two extraction theories. One was to oxidize the electrolyzed chromium to chromate(VI), reduce it to chromium(III) in aqueous solution, precipitate it as chromium hydroxide, dry it, and react it with magnesium powder in a thermite-type reaction to make chromium metal.

 

Another was to use the chromium(III) in aqueous solution and electrolyze it to produce chromium metal at the cathode.

 

Trying it was a different matter.

 

First, I anodized the spoon in salt water solution. A huge amount of metal hydroxides were produced. I filtered them and placed the paste in sodium hypochlorite to oxidize the chromium(III) to chromate(VI). However, I did not realize that the inside of the huge lump of hydroxides still had a large amount of unoxidized iron(II) hydroxide. The oxidation from iron(II) to iron(III) used up most of the oxidative power of the bleach, severely diluting the solution.

 

Then, I reduced the light yellow chromate solution with ascorbic acid. It formed, as before, a light purple solution of some chromium complex. However, the resulting solution was by now so dilute that nothing could really be done with it.

 

I took a small portion, added hydrochloric acid and reacted it with zinc metal. No chromium(II) ions were produced in a measurable quantity.

 

I then took another portion, larger this time, and added some ammonia. Apparently, chromium(III) hydroxide forms a complex with ammonia, preventing it from precipitating anything.

 

I then reacted the previous ammonia mixture with sodium carbonate. Nothing precipitated.

 

I then took some more chromium(III) solution and reacted it with sodium carbonate. Nothing precipitate. Apparently, chromium(III) forms a complex with ascorbate.

 

I then electrolyzed some chromium(III) solution. Nothing happened.

 

I reduced the remaining chromate to chromium(III) to avoid environmental catastrophe and dumped down the drain.

 

 

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Published by LanthanumK - in Experiments
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