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  • 1 Ecole Nationale Supérieure de Chimie de Mulhouse, Université de Haute-Alsace, 3, Rue Alfred Werner, F-68093 Mulhouse Cedex, France
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Pure alkali metal preparation is a complex problem: in most available commercial samples, all of them are simultaneously present. Conventional separation techniques are not always effective enough to reach parts per million total impurity levels. However, near the melting point, superficial segregation occurs. A zone melting derived technique coupled with a specifically developed solvent extraction process allows the total impurity content of sodium to be lowered below a few parts per million. The described thermal process, although using chemical reactions, is purely physically steered: it purifies as well potassium containing sodium as sodium containing potassium. 4 alkali metals are considered: Li, Na; K, and Cs.

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