Zinc Sulfate:
Zinc sulfate is the organic compound ZnSO4 as
well as any of the three hydrates. It was historically known as “White Vitriol”. All
of the various forms of colorless solids. The heptahydrate is commonly
encountered. It is on the World Health Organisation’s list of essential
medicines, a list of the most important medication needed in the basic health
system.
Production and reactivity: Zinc sulfate is produced by treating
virtually any zinc-containing material with sulphuric acid.
Specific reactions: the reaction of the metal with aqueous
sulfuric acid
Zn + H2SO4 + 7 H2O → ZnSO4•7H2O
+ H2
Pharmaceutical-grade zinc sulfate is produced by treating
high-purity zinc oxide with sulfuric acid:
ZnO +
H2SO4 + 6 H2O → ZnSO4•7H2O
In aqueous solution, all forms of zinc sulfate behave
identically. These aqueous solutions consist of the metal aquo complex
[Zn(H2O)6]2+ and SO42− ions.
Barium sulfate forms when these solutions are treated with
solutions of barium ions:
ZnSO4 + BaCl2 → BaSO4 +
ZnCl2
With a reduction potential of -0.76, zinc (II) reduces only
with difficulty.
When heated above 680 °C, zinc sulfate decomposes into
sulfur dioxide gas and zinc oxide fume, both of which are hazardous.
Applications:
The hydrates, especially the heptahydrate, are the primary forms
used commercially. The main application is as a coagulant in the production of
rayon. It is also a precursor to the pigment lithopone. Zinc sulfate is used to
supply zinc in animal feeds, fertilizers, and agricultural sprays. Zinc sulfate
like many zinc compounds can be used to control moss growth on roofs. It is
used as in electrolytes for zinc plating, as modern dyeing, as a preservative
for skins and leather and in medicine as an astringent emetic.
Safety:
Zinc sulfate powder is an eye irritant. Ingestion of trace
amounts is considered safe and zinc sulfate is added to animal feed as a source
of essential zinc, at a rate of up to several hundred milligrams per kilogram of
feed. Excess ingestion results in acute stomach distress, with nausea and vomiting
appearing at 2-8 mg/Kg of the body weight.
