Ferrous sulfate is an important source of divalent iron used across agriculture, animal nutrition, water treatment and various industrial processes. Commercial and naturally occurring ferrous sulfate exists in several hydration states. Among them, ferrous sulfate heptahydrate (FeSO₄·7H₂O) and ferrous sulfate monohydrate (FeSO₄·H₂O) are the most commercially relevant, while ferrous sulfate tetrahydrate (FeSO₄·4H₂O) is mainly encountered as an intermediate hydration phase. Alth

Although both products supply soluble zinc, the difference in crystal-water content significantly affects their zinc concentration, physical stability, storage requirements, processing methods and suitable applications.