Iodine has been used as a carrier in most experiments. At such concentrations, the effects of impurities can be very serious, especially for a halogen such as astatine, which exists in several oxidation states and can form many organic compounds. However, the rarity of astatine means that these solutions are extremely dilute, with concentrations around or below 10 −10 molarity (the number of moles per litre of solution). The amount of astatine is then calculated from the measured radioactivity of the reaction products. With the exception of a few spectrometric and mass-spectrometric studies, most investigations of astatine chemistry have used tracer techniques, which involve using chemical reactions in a solution with similarly reacting elements as carriers. Analysisīecause of the short half-lives of astatine isotopes, only very small quantities have been available for study. Alternatively, the halogen may be removed from the target by chemical methods, such as dissolving in nitric acid, with the latter being removed by boiling.Īnother procedure involves the use of a metallic thorium target, which-after bombardment-is dissolved in concentrated hydrochloric acid containing hydrogen fluoride and chlorine. If an aqueous solution of astatine is desired, the element may be separated by washing with an appropriate aqueous solution. The free element begins to distill at 271 ☌ (520 ☏, or the melting point of bismuth), but the operation is best carried out at 800 ☌ (1,500 ☏) with subsequent redistillation. From this, astatine may readily be removed by distillation in air from a stainless-steel tube. Metallic bismuth may be used as a target material. Which indicates that bismuth-209 takes up one alpha particle and emits x neutrons to form an isotope of astatine, whose atomic weight depends on the number of neutrons lost. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!Īn elementary quiz about fundamental matters.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century. ![]()
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