for which
pe -|- pH == 2.43 (14.16)
The dashed lines in Fig. 14.7 represent metastable equilibria. For example,
CuFe2O4(ferric ferrite) in equilibrium with soil-F e is always metastable with respect to soil-Cu. Below pe + pH of 11.53 where magnetite controls iron solubility cupric ferrite becomes even more soluble. The mineral CuOH(c) is always metastable to Cu2O(cuperite), and both are metastable to cuprous ferrite. The solubility of Cu J' in soils is expected to follow the solid lines shown
in Fig. 14.7.
Although Fig. 14.7 was constructed for pH 7.0, it can be easily interpreted for any pH. All lines in this figure move upward by one log unit of Cu* for each unit decrease in pH, but their relative positions remain unchanged with changes in pH.