Sciencemadness Discussion Board

Piranha solution from sodium percarbonate

Keras - 11-5-2019 at 06:29

This is a theoretical thought process only.

If (suitably cooled) concentrated sulphuric acid is added to sodium percarbonate, the carbonate part should be consumed, living only sodium sulfate (2 NaCO3 + 2 H2SO4 → 2 CO2 + 2 Na2SO4 + 2 H2O).

Thus, for each two molecules of water formed, three molecules of H2O2 should be released, since the adduct is composed of two sodium carbonate molecules for each three hydrogen peroxide ones. This should lead to a 66% peroxide solution, to which more sulphuric acid could be added to get a strong piranha solution.

Thoughts? Byproducts? Anything else? (There seems to be something about this in a Quora thread, but it doesn’t discuss the idea in depth.)

I suppose that if hydrochloric acid is substituted for sulphuric acid, the Cl- ion is going to be oxidised by H2O2 leading to chlorine gas and water (1.76 V for H2O2/H2O and only 1.35 V for Cl/Cl-), but that shouldn't happen with SO42-.

Dragonjack12 - 17-5-2019 at 06:41

I think there is a slim possibility if it is chilled.

Assuming higher concentrations I think that the CO2 bobbles will case some of the H2O2 will decompose. You could do the reaction / distillation under vacuum.

Sadly you will probably just get sodium sulfate carbon dioxide and water and maybe some O2

draculic acid69 - 17-5-2019 at 09:16

I don't think chlorine will form as sodium perborate and HCl results in perboric acid and nacl.

Keras - 19-5-2019 at 03:46

Quote:

Sadly you will probably just get sodium sulfate carbon dioxide and water and maybe some O2


I did that with HCl. Well, at home in my flat I have no access to glassware and all, so I just put some coins into HCl. No reaction. I added sodium percarbonate and suddenly things got crazy, and I ended up with multiple redox reactions at once between coins made of copper, bronze, nickel and iron. I also added aluminium, just to pepper the mix.

So hydrogen peroxide can very much survive sodium percarbonate dissolution in HCl, I suppose the same is true with sulphuric acid.

phlogiston - 19-5-2019 at 15:43

Quote: Originally posted by Dragonjack12  
Sadly you will probably just get sodium sulfate carbon dioxide and water and maybe some O2


No, he won't. It'll work more or less as OP envisioned, and yield H2O2 and Na2SO4. When concentrated solutions are used, much of the sodium sulphate precipitates and can be filtered off.

It possible to make solutions of 30%+ peroxide in this way. I recall a thread from someone that did this, but alas I can't find it anymore. I've used the above methode myself to make more dilute solutions when I could not buy hydrogen peroxide directly.
Anyway, I've used it myself to

Keras - 20-5-2019 at 01:00

Quote: Originally posted by phlogiston  

It possible to make solutions of 30%+ peroxide in this way. I recall a thread from someone that did this, but alas I can't find it anymore. I've used the above methode myself to make more dilute solutions when I could not buy hydrogen peroxide directly.
Anyway, I've used it myself to


That was unfinished, wasn't it? :)

Anyways, thanks! I'll try this when I have access to my lab. Also I made a mistake in the intial post. 2 molecules of water for each three of hydrogen peroxide make a 60% solution, not 66%.