Nitric acid is a powerful chemical compound that can dissolve many metals and other materials. Scientists write its formula as HNO₃, which tells us it's made of hydrogen, nitrogen, and oxygen atoms bonded together. When you see it in a laboratory bottle, it's a clear, colorless liquid, though old bottles sometimes look yellowish because the acid slowly breaks down in light.

This acid is extremely corrosive, meaning it eats away at things it touches. If you poured nitric acid on a copper penny, the penny would dissolve, releasing reddish-brown fumes and leaving behind a blue-green solution. Because it's so dangerous, only trained people in proper labs work with nitric acid, wearing thick gloves and protective goggles.

Despite its dangers, nitric acid is incredibly useful. Factories use it to make fertilizers that help crops grow, and it's important for producing some explosives and plastics. The chemical industry produces millions of tons of nitric acid every year. Jewelers sometimes use very diluted nitric acid to test whether a metal is real gold: gold won't dissolve in nitric acid, but many look-alike metals will.

Scientists discovered how to make nitric acid in large quantities in the early 1900s, which greatly changed agriculture by making fertilizer more affordable for farmers worldwide.