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Author: Subject: Determining the concentration of methoxide solution
SecretSquirrel
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[*] posted on 11-4-2014 at 06:50
Determining the concentration of methoxide solution


Hi fellow amateur chemists!

I got hold of some sodium methoxide solution that was not in its original container and the label said only "NaOMe soln." I have no idea how old this chemical is nor is it still any good. I want to somehow check the amount of methoxide present (if any) and I'm wondering if anybody knows a simple analysis method for measuring its concentration. I'd prefer titration or any other simple inexpensive method, friendly to amateur chemist with no access to fancy analytical equipment.

Any help is greatly appreciated!

[Edited on 11-4-2014 by SecretSquirrel]
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Galinstan
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[*] posted on 11-4-2014 at 07:06


surely a simple acid base titration will work just use an indicator like phenalthalien and see how much of a known concentration of acid it takes to neutrlise it.
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SecretSquirrel
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[*] posted on 11-4-2014 at 07:53


I'm not so sure about that, since sodium methoxide decomposes with water to give sodium hydroxide and methanol. I'm sure some of it already decomposed over time by absorbing moisture from the air and I would like to know how much methoxide is still in solution. Simple acid titration won't do, because by doing that I'd be titrating sodium hydroxide already present as well as sodium methoxide. As far as I know titration should be performed in a non-aqueous medium but I still don't know what this medium should be and what reagent I need to use.
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Galinstan
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[*] posted on 11-4-2014 at 12:28


titrations don't have to be performed in aquas solution you could do do the titration in methanol using an acid soluble in methanol , but doing it in water would be fine as adding an excess of water will form equal moles of sodium hydroxide as there where moles of methoxide so you could get your concentration that way :)

EDIT: sorry i missread your last post about the already present hydroxide ,im not sure then

[Edited on 11-4-14 by Galinstan]
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zed
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[*] posted on 11-4-2014 at 21:28


Fellers here abouts have posted simple methods for making fresh NaOMe. It isn't hard, and cost is minimal. Check the search engine. The topic has been much discussed.
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