Chlorine gas from KMnO4 and HCl?

[chembio]

Yesterday, I was experimenting with KMnO4 crystals and 33% HCl. When I added the acid to the KMnO4, the test tube misted up (but didn't heat up) and a hissing sound was heard. A brownish, shit-like gooey mess was formed at the bottom of the test tube.

Then, I noticed a pungent smell-not unlike that of chlorine gas-coming out of the test tube. It really stank, and my dog (which was sleeping nearby, maybe three feet away) yelped and ran off while shaking her head. My nose is still slightly raw :eek:

The question is: Shouldn't the KMnO4 have simply become acidified? Why did this reaction take place? :confused:

I repeated the experiment, and got the same results.

Are there any chemical tests for chlorine gas that do not involve litmus paper? I've yet to renew my supply...

[Charles Owlen Picket]

A daitomic gas, chlorine is a halogen whose oxides (that are strong oxidation agents) are easily tested for. See BERTHOLITE, the name of the gas as a weapon utilized in WW I - for ppm, general, and qualitative testing. It's a bleaching agent of course so a simple test (outside of smell & taste) is the minor bleaching of colored paper when exposed to same.

When I did a search for chlorine gas within the forum I found a few things, etc. You can get off to a good start that way.

[Zeitgeist]

Yes, this reaction will definately produce HCl, and lots of it.

The permanganate oxidises the Cl-.

If you want to acidify a redox reagent, you'll want something like sulfuric acid, or phosphoric maybe.

[Bugger]

That brown stuff formed by reaction of permanganate with HCl, or with an acidified solution of a chloride, would be MnO2, or a mixture of MnO2 and Mn(OH)3, formed by the reduction of Mn(VII) to (IV) and/or (III). Permanganate(VII) could be regenerated from this, after it is filtered out, by reaction with alkaline hypochlorite; or more satisfactorily electrolysis in a cold strongly alkaline solution, in which the Mn would dissolve as manganites(III) or (IV), and be oxidized by a sufficiently strong voltage at an oxidation-resistant anode in steps to the (VII) state. There is currently a thread on sciencemadness.org/talk about this.

[DF90]

As a word of warning, do not use conc. sulphuric acid to acidify permanganates... Manganese heptoxide (Mn2O7) is produced. It is a oily green liquid that is very explosive and reacts very violently with organic material. Further information about it can probably be found by doing a search.