... crystals; soluble in water, melts at 64 C. Fertilizer Ferrous Sulfate Heptahydrate Ferrous Sulfate Heptahydrate, also called copperas, ... as a substitute for aluminum sulfate, as a fertilizer, and as a feed additive. It is used ... as a substitute for aluminum sulfate, as a fertilizer, and as a feed additive. It is used ... matter,%,≤ 0.5 0.0015 Pb,%, ≤ 0.002 0.0002 As,%, ≤ 0.0005 0.0001 fertilizer FeSO4.H2O