Zinc
Zinc is a grayish metal, which quickly is covered by an
oxide layer, when exposed to air, but further corrosion only occurs at a very
low rate, once a protective layer is formed. Zinc is used for construction
purposes and roofs. Such constructions can last for tens of years. When the metal is finely powdered, then it becomes
much more
reactive. Once the fine powder is ignited, it can continue burning. Very fine
zinc powder is very dangerous. It is notoriously pyrophoric and quite some
accidents have happened in the past with very fine zinc powder, igniting
spontaneously.
Zinc is attacked quickly by mineral acids. It dissolves, forming hydrogen and colorless zinc (II) ions.
For the home chemist, zinc is an interesting compound. Fine filings or coarse powder can be used as a safe, but strong reductor in aqueous experiments. Zinc metal can be obtained at hardware stores. Fine filings can be made with an iron-saw. These filings are not pyrophoric. Sometimes, very pure zinc metal can be purchased on eBay at reasonable price in the form of large lumps. Sawing or filing of these lumps is necessary to make it suitable for chemistry experiments.
For practical purposes, one can assume that zinc only exists in the +2 oxidation state in its compounds. Compounds of zinc are only moderately interesting for the home chemist. Zinc ions are colorless and have no interesting redox chemistry and no colorful coordination complexes. Zinc is amphoteric. It forms an insoluble hydroxide, when a solution of a soluble hydroxide is added to a solution of a zinc salt. When more hydroxide is added, then the precipitate dissolves again, and a so-called zincate is formed. The metal itself is much more interesting for the home chemist than its compounds.
The following compounds can be obtained fairly easily by the general public:
- zinc oxide, ZnO
- zinc sulfate, ZnSO4·7H2O
Zinc
oxide is a white powder, which easily dissolves in dilute acids. It does not
dissolve in water. This can be used as a source of zinc ion for many other
experiments. Zinc oxide can be obtained at better equipped drugstores and at
paint and art stores as a white pigment.
Zinc
sulfate a very water soluble, transparent, colorless, crystalline compound. This
can be obtained at better equipped drugstores and at chemical supply houses.