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/
