This is the experiment that your audience will remember from your chemistry magic show. Here’s what happens – you call up six ‘helpers’ and hand each a seemingly empty test tube. Into each test tube, pour a little of the main gold-colored solution, say a few magic words, and their test tubes turn clear, black, pink, gold, yellow, and white. With a flourish, ask them to all pour their solutions back into yours and the final solution turns from inky black to clear. Voila!
I first saw a similar experiment when I was a kid, and I remembered it all the way through college, where I asked my professor how I could duplicate the experiment on my own. I was told that the chemicals used in that particular experiment were way too dangerous, and no substitute experiment was possible, especially for the color reversal at the end. I was determined to figure out an alternative. After two weeks of nothing but chemistry and experiment testing, I finally nailed it – and the best part is, you have most of these chemicals at the grocery store. (And the best part is, I can share it with you as I’ve eliminated the nasty chemicals so you don’t have to worry about losing an eyeball or a finger.)
NOTE: This experiment requires adult help, as it uses chemicals that are toxic if randomly mixed together. Follow the instructions carefully, and do not mix random chemicals together.
Are you ready to mix up your own rainbow?
Please login or register to read the rest of this content.
Please take a look at the Unit 8 shopping list for information on where to purchase supplies.
You will need test tubes for many chemistry experiments. Click here for Unit 8 shopping list.
Were do I find materials?
I don’t have test tubes. What do I use?
If it turns pink and then yellow, that most likely means that the solution wasn’t mixed before it was poured. While wearing gloves, hold a finger over the test tube and shake it (to stir) before pouring the contents into the other test tube. Reminder that remember phenolphthalein is an indicator, which means that it is colorless and will turn pink in alkaline solutions (bases) around 8.2 on the pH scale. The color change is not permanent, it will go clear again when the solution turns acidic.
Hi Aurora,
Quick question. We added the required 2 drops of phenolphthalein to our test tube, but when we added the Iodine and sodium carbonate solution it turned pink but only for a second or two then turned yellow. It was like a flash of pink only. Was there just not enough phenolphthalein to turn it permanently pink? Thanks!
Hi Aurora,
This experiment was great! We had to use an alternative for sodium thiosulfate, (vitamin C tablets), and we counldn’t get hold of some Phenolphthalein, but it worked just as well.
Just have one question: I would like to study Forensic science, and I was just wondering if you have anything on it, and if you don’t, if you could recommend a website, course or any other information on it.
Thank you,
Juliette, (13)
Maybe it’s the kind of water we have but if for example you put ice cubes in water, you will get these tiny particles of white at the bottom of you cup. Same with unopened water bottles wich you have frozen and thawed. Remember, they are brand new and unopened so it’s something that has not been added.
This experiment isn’t designed to be used with potassium ferrocyanide, so there’s probably another reaction going on. The iodine rainbow experiment is only supposed to have very specific chemicals combined to get this effect. Be careful when you combine chemicals, especially ones you’ve never combined before… you can get unexpected (and unwanted) results, like creating HCN gas.
White stuff at the bottom of water bottles? Where the bottles sealed, or had they been opened before? You say thawed, so they were frozen… are you sure the white stuff isn’t ice crystals?
Is the white stuff from this experiment, and if so, which step where you on? “White flaky stuff” is hard to pinpoint without knowing more. Sorry for being vague, but the more you can tell me about what’s going on from your end, the helpful I can be! 🙂
So can you tell us why we did not get Prussian blue? I know it probably could be a number of reasons but what are the most likely?
Right – now I understand what you’re asking. Sorry – that chemical wasn’t associated with this experiment, so I was a little fuzzy on what you were asking! Yes, Potassium ferrocyanide reacts with iron in solution to produce a dark blue precipitate called Prussian blue:
K+(aq) + Fe3+(aq) + [Fe(CN)6]4-(aq) ↔ KFe[Fe(CN)6](s)
A lot of metal ions form ferrocyanide precipitates, so potassium ferrocyanide is not a good reagent for separating metal ions, so most scientist use it just to confirm their results from a different test.
One more question. Joey noticed some white flaky stuff at the bottom of his thawed water bottles. Is that calcium or what? Thanks
potassium hexacyanoferrate is the name of the chemical. Doesn’t that detect metals in a solution by showing a blue color? Thanks.
I am not sure which chemicals you’re referring to. For this experiment, the iodine is used to indicate starch, not iron. You can detect iron in a solution but it’s kind of difficult, and it really depends on what the solution is made up of. You can read more about advanced techniques on this here.
No, but Tom Lehrer’s song includes most of the elements, and is under two minutes long. Look on our educational games page.
We used hexawhatever to find the iron in our water, which we know is there , but the liquid stayed clear. Do you know why?
do you know where we can find a good song that will teach us the elements in order?
Sure – there are in the electricity section here:
https://www.sciencelearningspace2.com/category/unit-10-electricity/lesson-1-circuits/circuits-experiments/
In e-Camp, I have a whole bunch more new circuits to do, including laser tag and a dozen more robots! Look for it this summer.
Aurora, I watched the e-science video and you said you could make burglar alarms, and trip wires. Do you have a video for doing them? I tried searching but no rusults 🙁
First, as a rule, make an effort never to get any chemicals on your hands while working in the lab – even if it’s just a lab at home. Wearing the gloves is an important safety procedure. That said, none of the chemicals in this lab are going to do much damage in the concentrations used. They could cause skin irritation, but not much beyond that. If you were to get some on your hand accidentally, flush it with water for a good 10-15 minutes. This should solve the problem. Be safe and have fun!
That was amazing! Just as an example, say I got some of the solution my hand. What would happen then?
Oops! Sorry for the typo. It should be non-clear, non-ammonia iodine. The clear stuff will work as well, only you won’t see the gold color initially. The experiment will work with clear and brown. Does this help?
Sorry, I’m a bit confused as to the type of Iodine needed. The text says to get “clear” iodine (which is what I bought) but in the video you say to use dark (or maybe brown) iodine, unless I misheard. I’m guessing that brown is what is needed because we didn’t get quite all of the reactions we expected.
Have you tried it yet? 🙂 That’s part of doing science!
what if you add to much vinegar?
My daughter and I are enjoying the chemistry unit immensely. Today, we did the iodine rainbow and marveled at your tenaciousness in recreating the experiment from chemicals around the house. You are a science-challenged homeschooler’s dream!