Conclave: the chemistry behind the black and white smoke

White smoke from the chimney on top of the Sistine Chapel (Vatican City) indicates that the Pope has been elected. MartiBstock/Shutterstock

This week, 133 cardinals have gathered in the Vatican to elect a new leader of the Catholic church. During their deliberations, the only indications of their progress are the regular plumes of smoke wafting from a freshly installed chimney perched on the roof of the Sistine Chapel.

Tradition holds that black smoke indicates the cardinals have not yet agreed on a new leader...