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Author: Subject: Need a Safe Extraction Demo
Capt Chaos
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[*] posted on 27-1-2012 at 05:06
Need a Safe Extraction Demo


So, got a class of suits that someone wants us to give a "chemistry demo" to.
Don't ask. It's complicated.
However, "office" environ stipulations: nothing too acidic, nothing too alkaline, nothing flammable, toxic, too hard to clean, yada, yada, yada...
So I've got the elephant toothpaste thing. That's about as benign as you can get.
But was thinking a color transfer extraction (related to subject, which I also can't talk about) would be apropos.
Simple--two liquids in a separatory funnel, shake, and a color transfers from one liquid to the other. Or something to that effect.
Damned if I can find anything 'for the office'.
Ideas? Something equivalent? I'm open to suggestions.
Okay, it's not mad science; more, irritating science at this point.

[Edited on 2012-1-27 by Capt Chaos]
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MrHomeScientist
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[*] posted on 27-1-2012 at 07:06


The blue bottle or chemical traffic light demos are pretty good, it's not an extraction but it is a color change and you can talk about oxidation and reduction. You simply shake the bottle and it changes colors as oxygen is mixed in, and it's repeatable many times.
The traffic light demo I do uses the following:
5g NaOH
3g Dextrose
very small amount of indigo carmine
250mL H2O

This makes a 0.5M solution of base, if that meets your alkalinity requirements. It's done in a sealed bottle so that should help. The blue bottle is the same prep, replacing indigo carmine with an even smaller amount of methylene blue. Disposal is also easy, just neutralize with acid until the solution turns persistantly blue (using either dye) and pour down the drain with lots of water.

Warning, though: I tried this in a plastic water bottle, and it did not work very well. I suspect something reacted with the plastic, and it only changed colors 2 or 3 times before petering out. I now do this in a screw-capped glass or nalgene flask, and the color change can repeat up to 20 times.
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Capt Chaos
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[*] posted on 27-1-2012 at 07:33


Thanks Mr. Home Scientist.

I am familiar with this, having seen it some time ago.

Could you give me a ROM on 'very small amount' of the indigo carmine? I guess we're talking just a pinch.

This actually would be a very interesting combo with the elephant toothpaste (sans soap), where the offgassing oxygen from that reaction could be bubbled through this to show the color change. A most benign 'reaction' indeed.
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MrHomeScientist
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[*] posted on 27-1-2012 at 08:50


I never precisely measure how much indigo carmine I add, for me it's down to what 'feels' right from experience. Just a small amount on the end of a spatula; it's not more than 100mg I'd say. If you use too much, the solution gets pretty dark and the colors are harder to see. If you use too little, it gets hard to distinguish the yellow from the green. For methylene blue, it's maybe half that amount. That stuff is powerful!

Quote:
This actually would be a very interesting combo with the elephant toothpaste (sans soap), where the offgassing oxygen from that reaction could be bubbled through this to show the color change. A most benign 'reaction' indeed.

That's a pretty neat idea actually, I bet that would work nicely! You could put the traffic light solution in a tall graduated cylinder or similar container and bubble the gas from the bottom for some very pretty results.

[Edited on 1-27-2012 by MrHomeScientist]
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neptunium
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[*] posted on 27-1-2012 at 09:56


you could show the detection of iodine in iodized kitchen salt
with corn starch ,distilled water and iodized salt...turns blue if Iodine is present...safe quick and easy




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Capt Chaos
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[*] posted on 27-1-2012 at 10:08


Truly harmless and shows analytical methods.
I will have my minions try this tonight.
Thanks
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Mr. Wizard
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[*] posted on 28-1-2012 at 08:21


Quote: Originally posted by neptunium  
you could show the detection of iodine in iodized kitchen salt
with corn starch ,distilled water and iodized salt...turns blue if Iodine is present...safe quick and easy

Doesn't starch turn blue in the presence of free Iodine? I understood the Iodine in salt was an iodide, not the free element. This would require something to oxidize the iodide to iodine to it could bind with the starch.

When using starch iodine test paper, it is initially white with potassium iodide and starch on the paper. The paper is moistened with dilute HCl and touched or exposed to an oxidizer, and the blue to black color of the paper indicates an oxidizer. It works with everything from organic peroxides to ozone.

If this demonstration works to indicate iodine in salt, I have to wonder what process releases the iodine. Could the CO2 and oxygen in air be reacting with the iodide to release iodine?

edit: corrected reduce to oxidize

[Edited on 29-1-2012 by Mr. Wizard]
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Capt Chaos
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[*] posted on 28-1-2012 at 08:32


The actual experiment requires the use of peroxide, but the comment is on the right track. The experiment should also be done with vinegar or it takes a really long time to see the results.
2H+(aq) + 2I−(aq) +H2O2(aq)→ I2(aq) + 2H2O(l)
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