Sciencemadness Discussion Board

Mixing hydrogen peroxide and acetic acid - is it dangerous?

xfusion44 - 23-12-2017 at 14:30


I'm making some copper acetate by adding copper metal to a solution of acetic acid (9%) - it's actually white vinegar. To this, I then add 30% H2O2. I think this reaction is quite similar to the PCB etching process, where HCl is used instead of CH3COOH. The acid itself does not react with copper but it does react with its oxide and since copper does not oxidize fast enough by itself, a solution of hydrogen peroxide is added to speed things up. At first, not much appears to be happening, but only a few minutes later, the reaction gets much more violent as the mixture heats up and it can get out of control easily if you add too much H2O2. When reaction ends, you're left with a nice dark blue solution of copper acetate. This can then be boiled down to obtain solid copper acetate - dark green solid, which can form really beautiful crystals!

However, I'm concerned that the mixture of H2O2 and vinegar could react to produce peracetic acid, which is toxic and highly unstable - wouldn't want to boil down that. If I understand this correctly, peracetic acid only exists in solution when those two reagents are mixed and can't be isolated, right? So if I accidentaly get this mixture on my skin would it be any more dangerous than H2O2 or vinegar on their own?

Thanks for your help!

Best regards, x

zed - 23-12-2017 at 17:09

I used to worry about Performic Acid. Peracetic Acid... Never made it.

But, Strike provides a decent procedure. What you are proposing, seems tame by comparison.

I wouldn't stop checking though. Got maybe half a dozen Youtube entries, not to mention folks hereabouts; who can give you tips on... what might or might not kill you.

[Edited on 24-12-2017 by zed]

[Edited on 24-12-2017 by zed]

softbeard - 24-12-2017 at 08:50

As with anything like this, danger is a strong function of the scale of your setup.
That said; nah, I wouldn't worry too much about peracetic acid forming in the situation you describe. The Cu should catalyze quick decomposition of both any H2O2 and peraectic acid formed from equilibrium. Standard corrosive materials precautions.
Acetic acid fumes when you boil down the solution is what I would be cautious about and prepare for.
I remember copper acetate forms these beautiful blue crystals,... Nice.

Hey Zed, thanks for the old MDMA synth ref., it was a great read. I can't believe the work & number of steps involved.

Edit: thank Zed

[Edited on 24-12-2017 by softbeard]

Metacelsus - 24-12-2017 at 13:25

The concentration of acetic acid you have (9%, before further diluting it by adding the hydrogen peroxide) is too low to form any substantial quantities of peracetic acid. Also, as stated in the above post, any peracetic acid formed would quickly be decomposed by the copper.

xfusion44 - 26-12-2017 at 06:49

Thank you all for your help! I am now quite convinced I can safely boil down the solution. I already did this once but at the time I wasn't aware of the possible formation of the peracetic acid.

Oh, and here are some pictures of my copper acetate crystals... I left the solution of copper acetate on the shelf in the wardrobe for about a year and forgot about it, until I found it in summer, this year - and I didn't even think that the crystals would grow in it (this wasn't even planned) so, when I discovered the jar, I was pleasantly surprised...

On the first picture, you can see, how the acetic acid slowly ate through the steel lid of the jar and left some brown compound behind (which I believe is iron acetate). On other pictures there are the beautiful copper acetate crystals I was mentioning before. Have a nice day :)

DSC01533 (1440 x 1080).jpg - 346kBDSC01534 (1440 x 1080).jpg - 555kBDSC01535 (1440 x 1080).jpg - 298kBDSC01538 (1440 x 1080).jpg - 216kB

xfusion44 - 26-12-2017 at 06:53

PS: those pieces of copper pipe that have crystals grown on them are about 18mm in diameter (0.7in).

aga - 26-12-2017 at 08:56

Cool !

They look a good size.

xfusion44 - 26-12-2017 at 13:31

Quote: Originally posted by aga  
Cool !

They look a good size.


I wish they'd look as good on the photos as they do in real life. I think the problem is just that you don't see them from different angles on the photo.

aga - 26-12-2017 at 13:43

In real life you see the equivalent of 100 photos a second, in stereo.

Take more photos and post them maybe ?

This looks like a really good candidate for hanging a seed crystal from a string.
It might take a year, but the crystals are awesome.

zed - 26-12-2017 at 19:08

Not entirely sure about acetic acid alone, eating your steel lid. There is a complex relationship between salts of iron/copper/silver, that I don't quite understand. My jeweler buddies, in the past, used an etching solution, that I didn't quite understand the actions of. When loaded with Silver, Just chews up native metals, and ppts native Silver.... Likewise, a solution of Cu, might decide to dump Native Copper, and tear up steel. Much more corrosive than mere acetic acid.

This stuff has its Mojo working!

chornedsnorkack - 28-12-2017 at 03:41

Danger of what?
Two different things:

With respect to explosion, it is said that peracetic acid is sold in mixture with acetic acid and hydrogen peroxide "to maintain its stability".
Meaning that a mixture which is still mostly peracetic acid is already much less explosive than pure peracetic acid.
Thus a mixture which is mostly acetic acid, hydrogen peroxide and water with only a small admixture of peracetic acid should be much safer again.

As for toxicity - is peracetic acid significantly more toxic than hydrogen peroxide?