Vatican Smoke
As the media and others await smoke arising from the Sistine Chapel’s chimney, Scientific American senior news reporter Meghan Bartels offers an explanation of the chemistry of the Vatican's white and black smoke signals. Reminder: white smoke indicates that a new pope, a successor to the late Pope Francis in this case, has been chosen by the Vatican’s cardinals, who have gathered in conclave. Black smoke: no consensus achieved.
How it works: The color of smoke derives from the color of small particles suspended in air, says pyrotechnics expert John Steinberg. The particles are the waste products of burning fuel with an oxygen-rich substance. In recent years, the Vatican used a mixture of anthracene and sulfur as the fuel for black smoke, with potassium perchlorate as the oxidizer. To get white particles in the smoke, the recipe calls for potassium chlorate and the sugar lactose as oxidizers. A pine resin called Greek pitch, which is rich in water, yields the white hue.
What the experts say: “That’s basically what this smoke is. It’s a dense fog of water droplets,” says Steinberg.
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