Occurrence and Production
Polonium is a very rare element in nature because of the short half-life of all its isotopes. It is found in uranium ores at about 0.1 mg per metric ton (1 part in 1010), which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers.
Because of the small abundance, isolation of polonium from natural sources is a very tedious process. The largest batch was extracted in the first half of the 20th century by processing 37 tonnes of residues from radium production. It contained only 40 Ci (9 mg) of polonium-210. Nowadays, polonium is obtained by irradiating bismuth with high-energy neutrons or protons.
Read more about this topic: Polonium
Famous quotes containing the words occurrence and/or production:
“One is absolutely sickened, not by the crimes that the wicked have committed, but by the punishments that the good have inflicted; and a community is infinitely more brutalised by the habitual employment of punishment than it is by the occasional occurrence of crime.”
—Oscar Wilde (1854–1900)
“An art whose limits depend on a moving image, mass audience, and industrial production is bound to differ from an art whose limits depend on language, a limited audience, and individual creation. In short, the filmed novel, in spite of certain resemblances, will inevitably become a different artistic entity from the novel on which it is based.”
—George Bluestone, U.S. educator, critic. “The Limits of the Novel and the Limits of the Film,” Novels Into Film, Johns Hopkins Press (1957)