Iron(II) nitrate is obtained in hydrated form by crystallization from solutions of
iron in cold dilute nitric acid,
4Fe+10HNO3 -> 4Fe(N03)2+NH4N03+3H20
or from the filtrate in the iron(II) sulphate-lead nitrate reaction. At room temperature it
crystallizes as the green hexahydrate; a 9-hydrate is stable below -10°. Solutions of the
nitrate are unstable to heat, nitric oxide being evolved and the iron being oxidized to
iron(III).
