Re: EDTA stability constants

The formation constant for FeEDTA is 25.1 (log Kmy). The formation 
constant for Mg is 8.7, for Ca 10.7, for Cu 18.8, and for Zn 16.5 (under 
standard conditions). As these are log values it is clear that EDTA binds 
iron MUCH more tightly than any other cation ... I dont think you have to 
worry about Fe being displaced. Info from Skoog and West, Fundamentals of 
Analytical Chemistry, 2nd Ed, 1969, p. 345.

Dr. dave.