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hot damn you can get disodium diammonium EDTA as a pool chemical? pure (ish)? hot damn. complexometric titration here I come #chemistry
anyway the idea would be (if you wanted to, like, use EDTA for complexometric determination of Mg or Ca): add ummeasured excess of BiHEDTA complex (or whatever) at a pH high enough for the Mg or Ca EDTA complexes to be stable. but Bi binds the EDTA much more strongly so basically there's no free EDTA, to start with
then electrolyze at constant current. the Bi gets reduced to metal, freeing the EDTA at a constant rate. it complexes any Mg or Ca present until it's all bound up. #chemistry
now I have a weensy bit of experience using EDTA for titration of metals in the old-fashioned way, with a buret and a visual indicator. there's some art to it...
...now, what I am curious about is whether a coulometric method can be devised. kinda hard to imagine. how do you dispense EDTA in proportion to a quantity of charge?
thought maybe...could you complex EDTA with a metal that (a) forms a really stable EDTA complex, and (b) can be reduced to metal electrolytically, freeing up the EDTA?