Zinc
Zinc is a chemical element. Its official symbol is Zn, and its atomic number is 30, which means each zinc atom has 30 protons in its nucleus. Zinc is not found in its elemental form. Instead, it is found in minerals with other chemical elements . For example, sphalerite is a mineral that is made of zinc, iron and sulfur. Sphalerite ore is mined in Australia and many other countries. Roasting (heating) the sphalerite separates zinc from the other components.
Zinc in sphalerite
Zinc is not found in pure elemental form but with other elements such as in this sphalerite mineral. On the periodic table, zinc is represented as Zn.
We use a lot of zinc – it is the fourth most widely used metal after iron, aluminium and copper. In 2017, worldwide use was over 14 million metric tons.
Elemental history
For 2,500 years, humans have mixed zinc with copper to make brass, an alloy. The ancient Romans and others in Middle Eastern regions used brass to make coins and ornamental items. The zinc they used was impure (mixed with other substances). It wasn’t until 800 years ago that experts in India discovered how to smelt minerals and ores to create metallic zinc.
Even though India recognised zinc as a metal in 1374 and an English metallurgist had patented a process to distil zinc in 1738, it was ‘officially discovered’ in 1746 by German chemist Andreas Marggraf. Marggraf received credit for the discovery because he published the distillation process in careful detail.
Industrial uses of zinc
Zinc is still used in the production of brass and bronze, just like it was thousands of years ago. A more modern use is in electrical batteries. Alkaline batteries have zinc powder inside them.
More than half of the zinc used today is to galvanise (coat) other metals like iron and steel. The protective zinc coating slows the metals from rusting or corroding. If you look closely at metal poles used in a chain-link fence or an outdoor handrail, you can see the protective coating.
Galvanised coating
Metals are galvanised – coated with zinc – to protect them from corrosion. The zinc coating often has a visible spangle.
Zinc compounds
Zinc compounds have a variety of uses. Zinc chloride is often added to timber as a chemical fire retardant. Zinc sulfide is used in fluorescent bulbs – it converts ultraviolet light to visible light.
Zinc oxide is used as a white pigment in paint. (If you have a set of oil paints, check to see if your tube of white paint has the word zinc in its name.)
Zinc oxide is used in sunscreen. It forms a barrier on the skin and reflects or scatters the UV waves. People who spend a lot of time in the sun – cricket players for example – may use a thick, white zinc cream on their nose or lips.
White Fern Sophie Devine
Sports people like cricketers often use zinc sunscreens to protect their skin when they’re in the sun for long periods. Pictured is New Zealand cricketer Sophie Devine after a match.
Most sunscreens look white at first but become clear when rubbed on the skin because the zinc oxide consists of tiny nanoparticles. There was concern that these nanoparticles might be dangerous, but a 2018 study showed that the tiny particles do not penetrate the skin or harm skin cells.
On the farm, zinc oxide drenches are used to prevent or treat facial eczema in sheep and cattle. It is a disease that damages the animal’s liver. The animals can also receive zinc in a pill form or in their drinking water.
Sheep being drenched
Zinc is used to prevent facial eczema in sheep. Sheep can be drenched with zinc oxide powder mixed with water, or they can be administered a slow-release capsule.
Nature of science
Not all science is done in the lab. In the 1940s, Gladys Reid – a farmer, dental nurse and citizen scientist living in Te Aroha – discovered that putting zinc salts in water troughs was the best prevention for facial eczema in livestock. Gladys recognised the importance of evidence and used control groups to test her ideas. Gladys’s remedy is still in use today!
Zinc and health
Zinc is an essential trace element for most forms of life. Human adults, on average, have 2–4 grams of zinc in their bodies. Most people get enough zinc from the foods they eat – meat, shellfish, eggs, legumes, pumpkin and sesame seeds, cashew nuts, potatoes and dairy products are good sources of zinc. Our bodies do not store zinc, so it is important to eat a wide variety of foods every day to replace it.
Zinc plays an important role in our immune systems and helps to heal wounds. There is evidence that zinc can help with the common cold if used within 24 hours of the symptoms appearing. Experts say more research is needed to determine the dose.
Not having enough zinc in our bodies can slow growth, interfere with our ability to reproduce, lower our immunity and interfere with our sense of smell.
Related content
The Parliamentary Commissioner for the Environment report Knowing what’s out there: Regulating the environmental fate of chemicals includes a case study of how zinc-based substances are used, regulated and monitored in New Zealand.
Useful links
Read the news release Realistic exposure study supports the use of zinc oxide nanoparticle sunscreens .
DairyNZ has information about facial eczema:
Read about citizen scientist Gladys Reid and her efforts to prevent facial eczema.
The National Institutes of Health website has a zinc health information fact sheet .
LiveScience Facts about zinc has information about the role of zinc in human reproduction.
