Persulfates (Peroxydisulfates)

[Zeitgeist]

Compounds like Sodium and Ammonium Persulfate are extremely powerful oxidants, and are readily available OTC from electronics suppliers for etching copper PCB's. Now, from my experience this stuff won't burn in a mixture with sucrose, so it must only act as an oxidant in aqeous solution, right?


S2O8(2-) + 8H2O --> 2H2O2 + 4H3O(+) + 2SO4(2-)

Correct me if i'm wrong, but assuming that's what happens, to what extent might this equlibrium go to?

[vulture]

Usually it forms HSO4 (-) instead of SO4(2-).
Also, I don't think H2O2 is present, not even as an intermediate species.

[Zeitgeist]

Well, thanks for the reply, i just guessed since it is made from H2SO4 and H2O2, perhaps electrolysis will yeild H2O2.

Yes, of course you won't have much SO4(2-), just like a H2SO4 soln. (slaps head)

[vulture]

Well, thanks for the reply, i just guessed since it is made from H2SO4 and H2O2

Not really. That's H2SO5 you're talking about, aka Caro's acid, piranha fluid or peroxomonosulfuric acid.

Peroxodisulfuricacid can only be prepared by electrolysis of sulfuric acid.

[Zeitgeist]

Damn, i was close.

Can you think of any pyro use for this stuff?

[vulture]

No. It's not because it has many oxygen atoms that it's a good oxidizer. Both of them will only liberate one oxygen atom per mole when decomposed. Which is peanuts considering their large mass.

They could be used to convert chlorates to perchlorates though.

[chemoleo]

persulfate can be actually made to burn, just mix it with sulphur powder... but beware of SO2, its nasty!
Vulture, do you have more on this, oxidation of chlorate to perchlorate with persulfate, or are you guessing??

[vulture]

S2O8(2-) + 2e- --> 2SO4(2-)

ClO3(-) - 2e- --> ClO4(-)
---------------------------------
S2O8(2-) + ClO3(-) --> 2SO4(2-) + ClO4(-)

left: 3- right: 5-

--> 2OH(-) ---> H2O

--> S2O8(2-) + ClO3(-) + 2OH(-) --> 2SO4(2-) + ClO4(-) + H2O

--> K2S2O8 + KClO3 + 2KOH --> 2K2SO4 + KClO4 + H2O

Now, I realize I equilibrated this for SO4(2-). Can't remember why.

The procedure works. Check Wouter Visser.

[blindreeper]

chemoleo, I don't think vulture would ever guess (well not often) about chemistry things, if you see him at sciencemaddness you will know he has a damn good knowledge of chemistry.

[Rhadon]

chemoleo, I don't think vulture would ever guess (well not often) about chemistry things, if you see him at sciencemaddness you will know he has a damn good knowledge of chemistry. You could say the same about chemoleo if you saw him over there :). But I think that he just said it to warn other people who read this topic.

[chemoleo]

Thanks for the little encouragement Rhadon:)
Anyway, Vulture, rather than the actual reaction (I checked it, it seems good :D), I wondered what conditions you'd need to achieve conversion of the chlorate ion to the perrchlorate ion (apart from high pH).
Like most of us, I got heaps of persulphate, and I am not so convinced of the heating mehtod anymore (to convert chlorate to perchlorate), despite a number of posts on it....
I just wondered what the efficiency was, etc.... I'd be working with NaClO3, rather than KClO3, so precipitation wouldnt be a possibility really.
Anyway, are you suggesting it would work by just mixing persulphate and chlorate in stoichiometric amounts, with the necessary amount of KOH?? Thats all?
Sounds too good to be true!!
Chemoleo

PS I asked whether he was guessing as there a number of people who postulate potential chemical reactions, which seem possible at a first glance but often turn out to be unworkable in real life. No offense to Vulture, or anyone. Just checking :)

[vulture]

Tsk, tsk, chemoleo, you're dissapointing me. High pH is only possible in solution, as solids don't have a pH.

I have not verified or performed this reaction myself, because I only have ammoniumpersulfate and I value my limbs and fingers.

Check the reduction potentials of S2O8/2SO4 and ClO4/ClO3 to check if it's possible or not. I don't have them at hand now.

EDIT: Heating method? Are you referring to 2KClO3 --> KClO4 + KCl + O2?

It does work. However, the decomposition of KClO3 straight to KCl and O2 is catalyzed by alot of transition metals. Try finding a heat resistant container that doesn't contain those...

[chemoleo]

tststs vulture, you are disappointing ME that you think I would think something like that!!! :D:D
REad my post properly pls, as I clearly never talked about the pH of a solid ;)

This is the overall reaction:

K2S2O8 + KClO3 + 2KOH --> 2K2SO4 + KClO4 + H2O

What do you notice on the left side of the equation? 2KOH.
What do you notice on the right side? H2O. Hence, the reaction would/could/should? be done in solution, as H2O is produced anyhow.

Hence, for this reaction to work at all, you need a *high pH*, which is a result of the KOH present in *solution*. (I thought of doing this in solution to start off with :), not to melt the whole thing together, as you seem to have thought!).

So, at least one condition of this reaction will be to have a high alkalinity, else the reaction aint going to work!!

See, this is why I asked to start off with, whether the reaction would work at all, cus I wasnt sure whether the oxidation potential of the S2O82- would be sufficient ot oxidise ClO3- to ClO4-.
Hmm, sadly I wouldnt know of a source where I could check this... I am not in possession of this kind of literature!

[cyclonite4]

persulfate can be actually made to burn, just mix it with sulphur powder... but beware of SO2, its nasty!
Vulture, do you have more on this, oxidation of chlorate to perchlorate with persulfate, or are you guessing??

Would you be able to provide an equation for that (for stoich, and knowing all the products), and would this be easily ignited, say, with a match?

[Jome skanish]

I wonder, HOW is persulfuric acid formed by electrolysis of sulfuric acid? I cant seem to figure out the reaction formula....

Could persulfate be formed by bubbling chlorine throgh a aquaeus sulfate salt solution?
2SO4-2 + Cl2 ----> 2Cl- + S2O8-2