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Author: Subject: HCl + H2O2 + Glass powder = vigorous bubbling/decomposition of H2O2 - Why?
RogueRose
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[*] posted on 10-3-2019 at 00:12
HCl + H2O2 + Glass powder = vigorous bubbling/decomposition of H2O2 - Why?


After crushing some glass I had a slight bit of rust mixed in with the glass (probably ~ 100mg) which turned the very fine glass brownish. I wanted to clean all the glass so I added some HCl & H2O2 (31.45% & 35% respectively) and 2 parts water, so I had about a 10% HCl concentration. The solution quickly turned yellow, looking very much like mellow yellow/ mountain dew. I notice before that heating the solution worked much faster, so I submerged the container (a PET plastic bottle) in ~160F water and stirred.

In about 1 minute the bubble production increased about 30-40x and it looks like the mixture is boiling. I assume that this is just the H2O2 breaking down, but this seems like a very low temp for this much of a reaction - especially since the temp dropped to about 150 after about 5 mins and the bubble production remained roughly at the same rate.

So is there a reason that the H2O2 is decomposing so vigorously at this low of a temperature? The glass is borosilicate if that matters, IDK if something in that helps facilitate the decomp.

Would the decomp be slower with a reduced concentration of HCl, or does it not matter very much. I don't smell any Cl2 coming off the mixture, I didn't expect to though.

I am a little confused about whether I'm getting FeCl2 or FeCl3 in some of these batches. The previous 2 I got a similarly colored yellow solution and then in another one a green solution (this one had a little stainless steel, so the nickel is probably coloring that the greenish color??).
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mackolol
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[*] posted on 13-3-2019 at 05:26


With that big excess of HCl to fe2o3 you're getting FeCl3 solution and fe3+ ions decompose h2o2 rather quickly. Also weak FeCl3 solutions are green
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Ubya
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[*] posted on 13-3-2019 at 09:25


Quote: Originally posted by mackolol  
With that big excess of HCl to fe2o3 you're getting FeCl3 solution and fe3+ ions decompose h2o2 rather quickly. Also weak FeCl3 solutions are green


FeCl2 is green, FeCl3 even if very diluted is yellow





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mackolol
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[*] posted on 13-3-2019 at 13:05


Right, my bad
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