Fig. 4. Effect of calcium–phytate precipitate (Ca_n–IP6), dodeca sodium–phytate (Na₁₂–IP6), and hydroxyapatite (HA) on soluble Co (A), Mn (B), and Zn (C) after equilibration for 136 h in 0.001 M CaCl₂. Error bars represent the standard deviation of the treatment means.