Date: Wed, 18 May 2011 13:31:31 -0500
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: larry.e.wilkinson**At_Symbol_Here**EXXONMOBIL.COM
Subject: Re: Piranha solution
In-Reply-To: <BANLkTi=8QaCCudpDVB6kaGht8jHNzhbOow**At_Symbol_Here**>

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.

Larry Wilkinson

             Jim Tung                                                      
             Sent by:                 DCHAS-L**At_Symbol_Here**LIST.UVM.EDU                 
             DCHAS-L                                                    cc 
             List                                                  Subject 
             05/18/11 09:41                                                
             Please respond                                                

Might the violent reaction between the solution and the ferric chloride be
the result of forming Fenton's reagent?'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?

Previous post   |  Top of Page   |   Next post

The content of this page reflects the personal opinion(s) of the author(s) only, not the American Chemical Society, ILPI, Safety Emporium, or any other party. Use of any information on this page is at the reader's own risk. Unauthorized reproduction of these materials is prohibited. Send questions/comments about the archive to
The maintenance and hosting of the DCHAS-L archive is provided through the generous support of Safety Emporium.