The Blue Bottle Experiment

NOTE: I say and write 10mL dextrose, but i mean 10g. There is clearly a bag of solid dextrose there. I have no idea how I messed that up!

Today we are going to be playing with the redox indicator methylene blue. Instead of KOH, it can be replaced with NaOH. It just needs to be adjusted according to molar mass.

Procedure adapted from:

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[kjpmi]

Interesting fact: Dextrose is the same as glucose as we think of it (it's obviously just the dextro- enantiomer of glucose but as far as commercial products they are the same). Our body can only use d-glucose for energy and it cannot use l-glucose. So only d-glucose (dextrose) is found in nature.
L-glucose can be made. It tastes indistinguishable from dextrose but since your body can't use it it doesn't have the calories that d-glucose has. It's also ok for diabetics since it won't raise your glucose levels. It is too cost prohibitive to use as a no calorie sweetener otherwise it would probably be on the market.

[derpingflamingo]

Holy crap for my undergraduate chemistry lab, we were given a solution really similar to that one (might be the same one!), and was told to use our analytical skills to identify the reaction steps. All we could come up with in a 3 hour time frame was that o2 was required (shook bottle in vacuum and nonvacuum), there are pressure drops at certain points of the reaction, and that the unknown compound has two states..

Thanks for the video!

[Inuyasha]

You can make a more interesting shake flask experiment by using Indigo Carmine, so called the "Chemical Traffic Light." It starts yellow, if you gently swirl the solution it turns red, if you shake it hard it turns green. I believe its made in a similar fashion as well.

[phillipdittmann]

Hey NileRed, there are some other interesting observations you can make in the blue bottle experiment:

1. Prepare three "blue bottles". One like in your video, the second one with 5x higher KOH concentration, the third one with a concentration half as high. Immediately after preparing the solutions, place them into sunlight. The colour of them should change to purple, depending on the concentration. (more KOH => more purple)

2. Let these three bottles stand for about a week. The colour should change to yellow, orange or red, depending on the KOH concentration.

Love your videos man!

[superdau]

I think unless specifically mentioned glucose is always dextrose/D-glucose, since L-glucose doesn't appear in nature.

[zachariahstovall]

You could use this for a bet. Saying you could turn water blue with magic.

[Noah-hzll]

So, if you were to displace the air in the bottle with something non reactive, say nitrogen or argon, it probably wouldn't be able to go back to blue, correct?

[LFTRnow]

I like making this in small ~5 ml bottles. Divide all the numbers at the beginning by 100 and add 1 drop of blue (its a lot so it is slower, but it works).

[chemresearcher]

At the Moscow Festival of Science we call this experiment as "The Hobbit, or There and Back Again"

[insecurecow]

You should 1 up Cody and backyard scientist by doing the bottle flip thing with this.

[alecapristrudel]

You can also do a much slower, less exotic version of this. You need a fairly dilute solution of copper(II) ammonia complex. Just stick a piece of copper metal in the bottle and wait. It turns colorless but it takes a long time (1-2 weeks for me), but the transition from colorless to blue is quite fast. CuCl2 makes a green version as per a Nurdrage video.

[coopersmith]

I did this experiment for my depth study in year 11 chemistry and it was so much fun!

[SourdoughVideo]

If anyone would like to understand why the solution is blue I would recommend reading about conjugated double bonds and HOMO LUMO transitions. In a very simplified somewhat incorrect synopsis, the more conjugation you have the closer the unstable and stable pi orbitals are which means that lower energy light is able to excite the electrons. This brings the emitted light into the visible spectrum allowing us to see it. This is how our shirts are colored and how sunscreen works.

[dividebyzeroisfail]

I use this reaction in my classroom every year. Thanks for the great video!

[WilliamEllison]

I can make toilet water turn Yellow in fewer steps.

[andrewburnett]

I would gladly listen to you at length talk about double bond conjugation, but I bet it gets pretty dry making a video like that, if not I'm just glad you make these fire videos

[acaterpillargivingbirth]

It looked familiar and I realised that we did this in my chemistry class ! We used sodium hydroxide instead of potassium hydroxide, that was fun

[jennifer]

this was SO much fun!!! we got to shake it 10x so far, and it's just so exciting every time! i'm going to send a bottle in to kindergarten with my daughter.

[somethingsomething]

Add a drop of a thin oil to seal off the top from oxygen so none of it is blue

[ObeyCamp]

I wonder if adding an amount of paraffin mineral oil to the bottle (just enough to cover the surface of the solution and separate it from the oxygen in the bottle) would work out well to prevent the top of the solution from turning blue until it's shaken. I don't know for certain if paraffin mineral oil would react with anything in the solution though. It's of pretty low reactivity, and it's just a 10-carbon chain with some hydrogens.

It could be an interesting way to get the solution perfectly clear if it would work the way I'm imagining. I've never actually taken a proper chemistry class though, so I don't know if this is nonsense or not.