>No, there are not any other cations, so I feel very strange. Everything
>brought from sigma.
Nothing's strange. EDTA is very poorly soluble at pH 4.2 and would
become even less soluble in the presence of 47% PEG. So it crystallizes.
Dima
>On Tue, Feb 22, 2011 at 8:58 PM, William Scott
><<mailto:[log in to unmask]>[log in to unmask]> wrote:
>What other cations are present? Any divalent cations like Mg++ or Ca++?
>
>The Ksp of magnesium phosphate is about 10^-24, so even if you have a very
>small amount present, say as a contaminant with citrate or EDTA, it will
>crystallize.
>
>On Feb 21, 2011, at 1:22 PM, Yibin Lin wrote:
>
> > Dear all,
> >
> > I got a lot of salt crystals in reservior solution (well solution),
> which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na
> 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone
> help me to explain why?
> >
> > Thank you very much!
> >
> > Yibin
> >
>
>William G. Scott
>
>Contact info:
><http://chemistry.ucsc.edu/~wgscott/>http://chemistry.ucsc.edu/~wgscott/
>
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