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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Mused on November 10, 2013, 12:50:53 PM

Title: Need help with analyzing boric acid from a solution
Post by: Mused on November 10, 2013, 12:50:53 PM

Hello everyone,
Could you please help me with the following:
I have to make an analytical protocoll to measure boric acid from the following compound:
Acidum boricum...0,6 g
Tanninum...3,0 g
Glycerolum....10,0 g
Ethanolum 96%..10,0 g
Aqua purificata.....10,0 g

Now i thought of an acid-base titration with either phenolphtalein or potentiometry (any other method works? like GC-MS?)
I guess boric acid and glycerol makes a stronger acid which can be titrated with NaOH, but won't Tannic acid interfere? Should I precipitate it with some kind of metal first, then filter it?

Thanks for your help in advance!

Title: Re: Need help with analyzing boric acid from a solution
Post by: Arkcon on November 10, 2013, 02:35:08 PM

Since this appears to be a pharmaceutical mixture, can you check the pharmacopeia for boric acid methods.  You guess right, that tannic acid will interfere with a titration.  Maybe you can still titrate, but also assay the tannic acid separately, then subtract?  Or can tannic acid be extracted away?

Title: Re: Need help with analyzing boric acid from a solution
Post by: Mused on November 10, 2013, 04:45:25 PM

The pharmacopoeia for boric acid only suggests acid-base titration with NaOH and phenolphtalein.
This is a manually made compund, so no method given. I think tannic acid can be extracted away, just not sure with what should I do it.