Zinc sulfate exists as the anhydrous salt (ZnSO4) and as three stable hydrates, the monohydrate (ZnSO4.H2O) hexahydrate (ZnSO4.6H2O) and heptahydrate (ZnSO4.7H20 (orthorhombic). Three unstable hydrates also exist, tetrahydrate (ZnSO4.4H20), dihydrate (ZnSO4) and heptahydrate (ZnSO4.7H20 (monoclinic). The main commercial preparation of zinc sulfate is the monohydrate, but it is sometimes sold as the heptahydrate. It is also available in solution.
Zinc sulfate may be toxic if ingested, based on unconfirmed animal information. For zinc compounds, including zinc sulfate, ingestion of large doses can cause anemia and stomach symptoms with nausea, vomiting, abdominal pain, diarrhea and, in severe cases, vomiting of blood, based on human and animal information. Zinc sulfate has been used therapeutically to induce vomiting.
Zinc is an essential nutrient for humans and animals. Both zinc deficiency and overexposure to zinc by ingestion have been associated with harmful effects.