Do you really want the solubility of Fe2O3? This dissolves very slowly except in strong acids, and dissociates upon dissolution.
There are links for the solubility of metals (including Fe+3) as a function of pH in thread161-50054
The solubility of Fe+3 can also be calculated as a function of pH from the solubility product, Ksp, of Fe(OH)3.
Ksp, Fe(OH)3 = [Fe+3][OH-]3 = 6 x 10-38,
so [Fe+3] = Ksp/[OH-]3, moles/Liter
and of course [OH-] = 10-[14 – pH]