DCHAS-L Discussion List Archive
Date: Wed, 18 May 2011 13:31:31 -0500
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From: larry.e.wilkinson**At_Symbol_Here**EXXONMOBIL.COM
Subject: Re: Piranha solution
In-Reply-To: <BANLkTi=8QaCCudpDVB6kaGht8jHNzhbOow**At_Symbol_Here**mail.gmail.com>
Iron(III) chloride "catalyzes" (not sure it is a true catalyst as the
resulting mixture ends up red-orange rather than the original
yellow-orange). the decomposition of hydrogen peroxide. I do a chemistry
demo wherein I add 1.5 g of iron(III) chloride (dissolved in about 10 mL of
water in a 20 mL vial) to 150 mL of 10% H2O2 (freshly diluted from the
commercial 30% solution) in a 1-L Pyrex graduated cylinder. If the 30%
H2O2 used was "fresh" (if not as "potent", use less than 100 mL of water
and 50 mL of H2O2), the mixture turns black/brown and effervesces. As the
exothermic reaction proceeds, it goes even faster, a column of foam rising
to near the top of the cylinder before the reaction subsides.
I can see where adding any solution containing >10% H2O2 to iron(III)
chloride would result in an immediate, violent reaction.
Regards,
Larry Wilkinson
Jim Tung
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Might the violent reaction between the solution and the ferric chloride be
the result of forming Fenton's reagent?
http://en.wikipedia.org/wiki/Fenton's_reagent
On Tue, May 17, 2011 at 1:20 PM, Johnson, Amy Carr wrote:
I have been reading about how to make Piranha solution and I keep coming
across this statement, "Add the acid to the peroxide, although some
authorities disagree" Why would authorities not agree that adding acid
to water instead of water to acid is best?
I have seen some say add acid to peroxide for initial solution, but when
refreshing, add aliquots of hydrogen peroxide to Piranha mixture. Is
that ok?
We recently had an incident when Piranha came in contact with ferric
chloride and instantly reacted
violently Was this due to the metal, the fact that both are oxidizers,
both, or something else?
I have read that neoprene gloves should always be worn. True?
What type of glass is appropriate for containment?
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