EDDHA Fe-6

Sodium ferric EDDHA — a 6% iron chelate that holds iron in solution at high soil pH, in the calcareous conditions where EDTA-chelated iron precipitates.

EDDHA is the most stable of the common iron chelating agents across the alkaline range, and it is specifically the ortho-ortho isomer that holds iron at high pH — so the number that matters is not the total iron but how much of it is ortho-ortho chelated. Typical material carries 4.8% w/w ortho-ortho of the 6% total against a 3.0% minimum, and stays in solution to around pH 9. The ortho-ortho figure is typical; the certificate of analysis reports it per batch.