Zinc: an orchestral metal
Zinc properties and areas of application
Zinc is a bluish-white metal coated with an oxide film. Its melting point is 420°C (787°F). Zinc powder tints flames a beautiful sky-blue color. Zinc is the 24th most common chemical element on Earth. The most widely-used zinc ore is sphalerite – zinc sulfide with iron impurities.
Zinc and copper form an alloy called brass, which was known thousands of years before the discovery of zinc as a separate element. Zinc as a separate element was supposedly discovered in India around 1300. However, the discovery of pure zinc is often attributed to German chemist Andreas Marggraf, as he described the process in detail.
Zinc is an active metal and can be used as a reducing agent to produce other, less active metals. For example, it can recover tin from an acidified aqueous solution of tin(II) chloride.
SnCl₂ + Zn → Sn + ZnCl₂
Zn + Sn²⁺→ Sn + Zn²⁺
When heated, zinc reacts with sulfur, producing smoke consisting of zinc sulfide and sulfur. The mixture burns with a bright yellow-green flame.
Zn + S → ZnS
Zinc has amphoteric properties, meaning that it can interact with both acids and alkalis. It dissolves vigorously in acids, such as hydrochloric acid, and reacts slowly in alkaline solutions.
Zn + 2HCl = ZnCl₂ + H₂
Zn + 2NaOH + 2H₂O = Na₂[Zn(OH₄)] + H₂
Zinc interacts with iodine with the addition of a few drops of water. The mixture heats up and some of the iodine sublimes, forming a violet vapor.
Zn + I₂ = ZnI₂
Zinc hydroxide is insoluble in water, but dissolves in an excess of alkali
Zn(OH)₂ + 2NaOH = Na₂[Zn(OH₄)]
Zinc is used to make alkaline and zinc-carbon batteries. Many musical instruments, such as saxophones, are made of brass. As zinc coatings can protect other metals from corrosion, iron bolts and screws are often zinc-plated, or galvanized. This “zinc defense” even saves ships from corrosion by seawater. Zinc oxide is used as a white pigment.
Zinc is an essential trace element for humans, especially children. Zinc deficiency can stunt growth, harm the eyes, and hurt the skin. Nutritional supplements containing zinc compounds are used to treat zinc deficiency.