In the selected obtaining method, [Fe(H2O)6]2+ and [Fe(H2O)6]3+
are both present in the reactor vessel, and, at the mixing stage with
ammonia, the abrupt pH rise favors the hydrolysis and promotes
burst nucleation of polymeric species [33,34] derived from the two
solvated iron cations, as initial concentration is larger than the
saturation one. The result is the formation of magnetite embryo.
The formation of magnetite embryos are favored here because of
the presence of Fe(II) and Fe(III) in a 1:2 stoichiometric
relationship, provoking a chain of the so-called olation and
oxolation acid–base reactions