Talk:Piranha solution

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Source Material

Large sections of this article, particularly the preliminary paragraph and the "Mechanism of action" section seem to have been lifted from this web page. Is this a case of wikipedia plagarizing the web, or vice versa? Does anybody have the tools to tell the difference? Is the solution to rewrite this page, eliminating some of the jargon that lead me to that site and maybe citing it in the references? Thought I'd ask before ripping apart the text. Zolot (talk) 16:07, 28 November 2012 (UTC)[reply]

Another issue is that none of the mechanism of action section is cited, and as noted before, the chemistry seems implausible at best. I'm currently researching the subject, so if I find a good source I'll come back and clean up the section. Otherwise, it may be best just to delete the section. No information is better than wrong information in my book. --Heptazine (talk) 14:27, 12 December 2012 (UTC)[reply]

?

isn't "Peroxymonosulfuric acid" the same thing?

I don't think so, primarily for this reason (thanks to rw): piranha solution ages and becomes less effective over time, presumably due to the formation of peroxymonosulfuric acid. I'll try to add a bit about that later (but anyone else? feel free!) --Terry Bollinger 03:39, 27 July 2006 (UTC)[reply]

It is chemically identical. H2SO5 is the product in both reactions. Caro's acid, piranha solution, or peroxymonosulfuric acid decomposes rapidly and is therefore only produced in situ and immediately prior to use.SuperFluid 21:49, 6 July 2007 (UTC)[reply]

"One must always add the peroxide to the acid, not the other way around."
Shouldn't that be the other way around? i.e. First rule of chemistry class is NEVER mix anything into an acid.

I agree with the poster above. I often use piranha solution to clean glassware and I always pour the sulfuric acid onto the hydrogen peroxide solution. The idea being that because sulfuric acid has a sizeable enthalpy of mixing, i.e. it heats up when diluted. So when you add something, your small amount of water heats up and will boil and splash and if you do it the other way round you have more water to absorb the heat so you will diminish splashing. Another useful thing to know is to use a big enough beaker, at least twice the volume of the piranha solution you want to make. 134.58.253.113 15:56, 15 February 2007 (UTC)[reply]

I have mixed it using both methods and have never experienced any sort of problems with boiling over or splashing, as long as the addition is done slowly and at RT. For simplicity, I instruct people to follow the "AAA" rule--always add acid (when diluting acids). This is simply for consistency and so that you do not initially make a very concentrated solution of acid by adding a small amount of diluent.SuperFluid 21:58, 6 July 2007 (UTC)[reply]

I disagree; I believe adding the peroxide to the acid is the safer method. Yes the exothermic enthalpy of mixing is an issue (and one should be careful that it does not splash out of control), but the bigger safety issue is preventing explosions. The likelihood of a hydrogen peroxide solution detonating depends on the concentration of hydrogen peroxide. For this reason, in three component systems with organics, water, and hydrogen peroxide, the hydrogen peroxide is always added last to minimize it's concentration. While I can't be certain, I would assume the same rule of thumb would hold true for piranha solutions. Heptazine (talk) 22:00, 12 October 2012 (UTC)[reply]

I believe the "Chemistry" section needs attention. To my knowledge, the equation is wrong and should be written to reflect the formation of H2SO5, not elemental oxygen. The NASA reference to atomic oxygen does not have bearing in aqueous chemistry. Strong acids (and bases) are known to clean organic residues from glass and other surfaces. H2SO5 is a very strong acid. There is no reference (that I have seen) for the formation of atomic oxygen in aqueous solution.SuperFluid 22:20, 6 July 2007 (UTC)[reply]

The chemistry does look bizarre and the NASA reference is irrelevant (removed). Expert tag added. 84.92.241.186 20:08, 19 October 2007 (UTC)[reply]

The solution would most likely contain sulfuric acid, peroxysulfuric acid and free H2O2 in equilibrium. An educated guess, though, would place the actual oxidizing agent as the protonated H3O2+ cation, which - by virtue of its electophilicity - can be attacked even by weak nucleophiles such as benzene or other aromatics in the fashion of epoxidation reactions, or hydride donation from hydrocarbons (the C-H sigma bond acting as a nucleophile) to give water and a carbocation.--Triflic Anhydride (talk) 10:05, 18 October 2009 (UTC)[reply]

As a further note, I would like to correct Superfluid regarding the strength of H2SO5 as an acid; it is most likely weaker than sulfuric acid because of the alpha effect increasing backdonation into its orbitals and making it harder to delocalize negative charge. Its oxidizing power comes not from its strength as an acid (though H+ is still a good oxidizing agent), but a combination of its weak O-O bond and good leaving group (bisulfate).--Triflic Anhydride (talk) 10:21, 18 October 2009 (UTC)[reply]

The equations are clearly in error - at one point an extra carbon appears out of thin air (reaction of the O. with C=C). Also they're inconsistenat as to whether they label the carbons or not, with no logic for the inconcistency present. 128.40.76.3 (talk) 09:49, 23 July 2012 (UTC)[reply]

Stoichiometry?

What is "a 3:1 mixture of ammonium hydroxide (NH4OH) with hydrogen peroxide"? According to the article on "ammonium hydroxide" this term is used for aqueous ammonia in any concentration. So how do I prepare a 3:1 mixture of aqueous ammona (concentration unknown?) with hydrogen peroxide? Beryllium-9 (talk) 11:01, 29 February 2012 (UTC)[reply]

Yes the article is unclear. It is a 3:1 mixture, by volume, of the common commercial grade of ammonia (28-30 wt %), and the common commercial grade of hydrogen peroxide (30 wt %). --Rifleman 82 (talk) 19:00, 29 February 2012 (UTC)[reply]

Current version contains nonsense?

"Piranha should be prepared by adding the acid into the acid, not the other way around" What? I see that there's been some disagreement about how it was before, but the way the article is currently written is clearly wrong. 70.72.163.248 (talk) 04:31, 16 March 2012 (UTC)[reply]

Etymology

It would be nice to have an etymology. This would probably require historical research (like the rediscovery of the first emoticon) in order to find the person who (possibly) named it after the ravenous fish, and why. ArthurDent006.5 (talk) 12:06, 28 July 2013 (UTC)[reply]

Safety

Am I the only one who thinks that this article is written such that it is giving advice on how to execute a potentially dangerous mixture? The name and chemical composition of the solution with a disclaimer that it is a potentially hazardous activity should be sufficient. There is no good reason to also tell readers to "heat this" or "let that sit overnight" -- especially on matters of opinion ("some feel it should be discarded as hazmat, others that it can be safely dumped with 'copious' amounts of water").

This article is just asking for trouble.