# Elephant Toothpaste demo: How to concentrate hydrogen peroxide (freezer?)

I would love to do an 'elephant toothpaste' demo in my Chemistry classes this week, but I do not have enough time to order 30% $\ce{H2O2}$ from a supply company. I have been reading (and seeing on YouTube), however, that some people choose to create their own concentrated $\ce{H2O2}$ (concentration allegedly in the vicinity of 20-35%) by putting 3% $\ce{H2O2}$ in the freezer overnight, then separating the concentrated $\ce{H2O2}$ from the then-frozen water.

My ideal plan would be to use all of the $\ce{H2O2}$ that I produce during my classes throughout the day. I've never worked with concentrated $\ce{H2O2}$ and so would like to ask.

1. Would anyone here actually recommend this method to me, given that I would be using this in class for the Elephant Toothpaste demo? Are there any safety-related deal-breakers that I should be aware of?

2. What is the highest possible concentration of $\ce{H2O2}$ I could feasibly achieve by storing a bottle in a school's lunch-room freezer overnight? I don't need anything above ~30% and would just love to know if this method has the potential to make >35% concentrations.

3. If I do happen to have extra $\ce{H2O2}$, what is the simplest way for me to dispose of it responsibly? I know that $\ce{H2O2}$ will eventually decompose into $\ce{H2O}$ and $\ce{O2}$, and would rather not have to find a way to store home-made $\ce{H2O2}$ of an unknown concentration, but want to be safe and responsible with any disposal methods I use.

• It is a very very bad practice to put chemicals in a fridge used for food storage. It is a safety consideration that you shouldn't violate. Especially if there are others that don't know about the "experiment." – MaxW May 22 '17 at 3:56
• @MaxW I appreciate your concern, but I am not sure what you are trying to warn me of. Some of the substances found in home refrigerators are what we might think of as "chemicals" (not specifically intended for consumption), such as baking soda (an open box is often used to enhance "freshness"), vinegar (effectively diluted acetic acid), and even gel-based cold packs generally kept in freezers. If we really want to go into detail, we could accurately say that everything in a refrigerator is a "chemical" product. Hydrogen Peroxide decomposes into water and oxygen. Is there a specific risk? – Year1HSChemTeacher May 22 '17 at 4:10
• @MaxW I'm sorry, the rest of your comment was initially hidden, and I didn't get past the first sentence. If I were to tell my colleagues not to touch the freezer bottle (I know they would not), what are the specific potential safety risks that I would be taking? I definitely understand that if someone were to take the bottle out and start fiddling with it, there could be problems, but the same would go for the rest of my chemical supply. If everyone were to heed my request, should I have any reason to think that the H2O2 would damage or contaminate anything in the fridge or freezer? – Year1HSChemTeacher May 22 '17 at 4:19
• My point is simply that you shouldn't try to rationalize that putting chemicals in a school lunch fridge is safe. Anytime that you're sure that you've made something idiot proof, you've vastly underestimated the intelligence of idiots. // I'm a chemist, so I fully understand that a strawberry is a bag of chemical;s. ;-) – MaxW May 22 '17 at 4:23
• I have seen a number of youtube videos that are extremely reckless. Often a basic safety requirement like safety glasses isn't met. What happens if you dump the acid on yourself? Where is the safety shower and eyewash? – MaxW May 22 '17 at 4:45