The classic smoke bomb
, instant fire demonstration
, and dancing Gummi bear demonstration
all have purple flames. The purple color is caused by oxidizing the potassium salts used in those projects. If you sprinkle lite salt (KCl) on a candle flame or a fire in a fireplace, you can get purple flames without the smoke of the smoke bomb or highly energetic combustion of the demonstrations. Other potassium salts also burn purple.
In addition to imparting a violet color to flames, potassium is the second lightest metal. The pure metal is silvery, but the element is so reactive, it's rare to see in pure form. Potassium spontaneously ignites in water and oxidizes very quickly in air.More Potassium Facts
Photo: Potassium produces a characteristic purple flame in the flame test. (Herge)