What do do with this 35% food grade H2O2 (Hydrogen peroxide)?

April 16, 2015 12:41 PM

I have a small dropper container with about half an ounce of H2O2 with a rubberish top (the part that you use to make the drops). I was using it for something a few months ago and I forgot about it and it has been sitting in my kitchen for about 2 months. Today I noticed the rubbery part has expanded a bit. I'm not sure what to do with it because I remember my chemistry teacher saying that H2O2 can be dangerous stuff. Can I open the container? Should I just toss the container?
posted by eq21 to Science & Nature (12 answers total)

Hydrogen peroxide decomposes pretty readily into plain old water and oxygen. There's nothing unsafe about opening the jar, but I wouldn't be surprised if it's not worth using any longer. I still would try to avoid getting it on your skin, though.
posted by backseatpilot at 12:45 PM on April 16, 2015 [5 favorites]

Yeah, as H2O2 decomposes it'll generate quite a bit of gas, which is why you're seeing the expansion. I don't think you have a lot to worry about with just half an ounce, and it's probably getting a bit long in the tooth anyway, so you might as well toss it. Put it in a ziploc bag and open it through the bag so you can contain any spill in case it fizzes over (it won't explode or anything though) since IIRC a concentration of 35% is approaching skin-burny range. Then toss it.
posted by un petit cadeau at 12:57 PM on April 16, 2015 [2 favorites]

Be careful opening it so you don't get sprayed. Then pour it down the drain with a bit of water.
posted by ryanrs at 12:59 PM on April 16, 2015 [1 favorite]

Here's a safety data sheet for 35-50% hydrogen peroxide. Nasty stuff so don't get it on you or in your eyes or inhale, but if you dilute it with water, you can wash it down the drain.
posted by smackfu at 1:10 PM on April 16, 2015

The gas is just oxygen. It's caustic stuff at that concentration, but it's not super dangerous. Treat it like you would a bottle of bleach. Don't put it on your hands but it can go down the drain with some water.
posted by phunniemee at 1:55 PM on April 16, 2015

You could do a scaled down version of the Elephant's Toothpaste demonstration. Obviously follow the safety guidelines.
posted by Esteemed Offendi at 2:00 PM on April 16, 2015 [2 favorites]

Concentrated h2o2 can cause nasty burns on contact with skin. I don't remember enough of the specifics from my chemistry days to say if 35% is concentrated enough to be really hazardous. I'd just throw it out without opening.
posted by DarkForest at 3:07 PM on April 16, 2015

No, 35% peroxide is too hazardous to be thrown in the trash, which may be handled by people and sorted for recyclables, depending on where you live. Rinsing it down the drain is the right way to dispose of it.
posted by ryanrs at 3:41 PM on April 16, 2015 [3 favorites]

You could dilute it and turn it into color-safe bleach and use it in your laundry.
posted by jeffamaphone at 4:31 PM on April 16, 2015

I can confirm that 35% H2O2 is definitely within skin-burning range, since I work with 20% routinely and have been careless enough to splash tiny drops on my arms a few times - it stings quite a bit and leaves a little red mark.

So be careful when you open it, wear rubber gloves or something, and make sure it doesn't somehow splash into your eyes, but otherwise yeah, that amount will be fine flushed down the sink with lots of water.
posted by randomnity at 4:54 PM on April 16, 2015

For the home version of elephant's toothpaste, all you need is baker's yeast and some dish soap. It's a good deal of fun.

Just be careful not to get the undiluted stuff on your skin, but to add to the chorus: it's quite safe to rinse down the sink.
posted by invokeuse at 6:03 PM on April 16, 2015 [1 favorite]

Best answer: If you fill your sink and hold the bottle underwater before unscrewing the top, half a fluid ounce of 35% peroxide will get diluted to complete harmlessness as soon as the top comes undone. Any gas that escapes is likely to be rich in oxygen, but again this will dilute to harmlessness as soon as it breaks the surface of the water.
posted by flabdablet at 8:08 PM on April 16, 2015