Gualterio_Malatesta
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Moisture and oxygen sensitive compounds.
Hey guys!
Is there any compound (or reaction that yields aforementioned compound), that is sensitive both to moisture and oxygen in the air, and that changes
it's color when exposed to those factors.
Why I ask, is that I have never worked with protective atmosphere (argon) before, and instead of spoiling expensive reagents due to sloppy workup, I'd
like to have me a little practice.
If this "indicator" compound doesn't change color then I'm good to go and experiment with real stuff.
[Edited on 13-6-2011 by Gualterio_Malatesta]
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Picric-A
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Preperation of Chromium (II) acetate would be a good start. Your product should be a bright red. If the slightest amout of air got in discolouration
would occur.
Copper (I) chloride is slightly less sensitive but will also work.
www.unf.edu/~michael.lufaso/chem3610L/inorganic_lab_report4....
[Edited on 13-6-2011 by Picric-A]
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DJF90
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There is a large difference between handling an atmospheric sensitive chemical and isolating it. Which do you wish to do? If the compound is really
sensitive to moisture and oxygen and you want to isolate it then you might be looking at the purchase of some very expensive Schlenk glassware.
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Gualterio_Malatesta
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No there's no need in isolation of the compound.
2 Picric-A
Thanks, I'll look into that!
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Magpie
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I have some CaCl2 granules that are deliquescent. They will liquify right before your eyes due to the moisture in ambient air. They are also cheap
and you should be able to find them locally OTC. Mine are for increasing swimming pool hardness, but I've seen them for sale for general drying in
smaller quantities too.
The single most important condition for a successful synthesis is good mixing - Nicodem
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garage chemist
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The best oxygen and moisture indicator that I know is a solution of sodium benzophenone ketyl.
The solution has an intense, deep blue color, like royal blue ink.
It immediately turns colorless upon exposure to moisture or oxygen.
It can be prepared as follows:
Put 100ml reagent grade 1,4-dioxane in a flask, add 1g sodium cut into thin slices. Put on a reflux condenser with calcium chloride drying tube and
reflux for 12-24 hours (or overnight plus most of the next day). The sodium will melt into droplets, and the initial gas evolution at the metal should
have completely subsided after the reflux. Most of the sodium should still be present.
Now add 0,2g benzophenone and continue refluxing under exclusion of moisture.
After some time (anywhere between 1-12 hours), the solution will have turned a striking deep blue or purple color.
If you now turn off the heat, the condensing and therefore contracting vapor above the hot dioxane will pull some air through the drying tube and
condenser into the flask, and the blue color will vanish within a few minutes, from the top downwards.
Upon refluxing again, the color is quickly restored.
The blue color can only be kept when no air is allowed to enter the flask upon cooling, e.g. by bubbling a slow stream of pure argon through the
solution.
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jzhhua
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Schlenk glassware is necessary to you
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ScienceSquirrel
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Sodium napthalenide is easily prepared as a deep green solution.
It is interesting as it is a radical anion, it is a useful reagent and it is pretty air sensitive as well.
http://en.wikipedia.org/wiki/Sodium_napthalenide
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Gualterio_Malatesta
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Thank you, thank you all. Very interesting info!
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