Zinc Sulfate
Properties
| State | Solid (white crystalline powder) |
| Color | White (colorless in solution) |
| Solubility | Highly soluble in water (576 g/L at 20 °C) |
| Melting Point | 680 °C (anhydrous, decomposes) |
| Boiling Point | Decomposes before boiling |
About Zinc Sulfate
Zinc sulfate is the most-used water-soluble zinc salt across medicine, agriculture, and industry — ZnSO4, molar mass 161.44 g/mol anhydrous. The historical name is white vitriol, the third member of the medieval-alchemical vitriol set alongside blue vitriol (CuSO4·5H2O) and green vitriol (FeSO4·7H2O) — all three were known by 1500 and all three are still used today. The lab-bench form is the heptahydrate ZnSO4·7H2O, isostructural with epsomite (MgSO4·7H2O), which is why it crystallizes into the same prismatic needles you've seen with Epsom salt. Pharmacologically, zinc sulfate is the standard zinc supplement for treating zinc deficiency — over 2 billion people worldwide are mild-to-moderately zinc-deficient by WHO estimates, and zinc-supplementation programs for childhood diarrhea reduce mortality measurably in low-income countries. Agriculturally, zinc sulfate is the most-applied zinc micronutrient fertilizer for rice, corn, and pecan in zinc-deficient soils, where the deficiency causes yield losses of 20-40%. Industrially, ZnSO4 is a coagulating agent in the viscose process for rayon fiber production, the electrolyte in zinc-electroplating baths, and a textile mordant.
Where you'll encounter it
If you've ever been told to take a 25 mg zinc lozenge at the first sign of a cold, the active ingredient was a zinc salt — often zinc sulfate or zinc gluconate — at a dose calibrated to deliver enough Zn2+ to interfere with rhinovirus replication in the upper airway. In a viscose rayon plant, the regenerated cellulose filament emerges from a spinneret into a coagulating bath of dilute H2SO4 saturated with ZnSO4 and Na2SO4, where the zinc fine-tunes the coagulation kinetics that determine fiber strength. In a Midwestern cornfield with zinc-deficient soil, a typical pre-plant application of 10-25 lb/acre of zinc sulfate corrects the chlorotic-leaf symptoms that limit yield. And in any general chemistry teaching lab, the zinc-copper Daniell cell — the textbook galvanic cell — uses ZnSO4 as the zinc-half-cell electrolyte sitting across a salt bridge from a CuSO4 solution.
Common Uses
- Oral zinc supplement for treating zinc deficiency and shortening common-cold duration
- Zinc micronutrient fertilizer for rice, corn, and pecan in zinc-deficient soils
- Coagulating agent in the viscose process for rayon fiber production
- Electrolyte in zinc-electroplating baths for steel-corrosion protection
- Zinc half-cell electrolyte in Daniell-cell electrochemistry teaching experiments
Safety Information
GHS: Acute toxicity oral Category 4 (H302), Skin/eye irritation Category 2 (H315/H319), Aquatic acute Category 1 (H400), Aquatic chronic Category 1 (H410). Acute oral LD50 in rats is around 920 mg/kg for the heptahydrate. Ingesting more than 200 mg of elemental zinc causes nausea, vomiting, and gastric upset; chronic high doses (>40 mg/day for adults) interfere with copper absorption and cause secondary copper deficiency. There is no specific OSHA PEL for zinc sulfate; treat as a particulate not otherwise regulated, 15 mg/m3 total / 5 mg/m3 respirable. The aquatic-toxicity hazard is the bigger concern — Zn2+ has 96-hour LC50 values for trout under 1 mg/L — so route waste through wastewater treatment that precipitates zinc rather than discharging to surface water.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.