Local News

You Owe Rockets' Red Glare to Chemistry

Posted July 3, 1998

— Picnics, parades and especially fireworks-- for many, it wouldn't be a holiday without a them. Every year, fireworks light up the sky to celebrate freedom. WRAL took a behind the scenes look at the fourth of July fire power.

The rockets' red glare in this weekend's fireworks shows, and the yellow, green and blue, for that matter, are all determined by chemistry.

"The color is determined by the element," explains Bill Switzer of NC State. "How much light is given off is determined by the heat of the flame."

Switzer, a chemistry professor at North Carolina State, not only enjoys setting things on fire. He likes knowing why fireworks do what they do.

While pyrotechnics have grown far more advanced over the years, the actual chemicals used in fireworks are still very common, In fact, you can find most of them in your neighborhood drugstore. For instance, table salt, or sodium chloride, when ignited, produces the orange-yellow you see in the sky.

"The boric acid, when it burns, burns with a characteristic green flame," Switzer says.

Boric acid is also commonly used to treat eye infections. Lithium found in batteries or depression medication is responsible for the rockets' red glare.

As for those ear splitting explosions. When black powder is burned, gases produced build up pressure. If the gases are contained, they eventually force their way out and blow up. If they are given a way to seep out slower, they will spew colorful flames.

"I am fascinated by fireworks, now maybe more than when I was a child," admits Switzer. "Partly because I understand a little better how they work."

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