Hafnium: Iodide Vapour Split on a Tungsten Wire Heated beyond 1600 °C (van Arkel and de Boer, US 1,671,213)

Hafnium will not come out of its chloride and hydrogen as clean metal. Van Arkel and de Boer instead let the vapour of hafnium iodide pass a white-hot wire in an evacuated vessel: the iodide splits and pure hafnium grows on the wire. Result: hafnium metal deposited on the wire. Source: A. E. van Arkel and J. H. de Boer, US 1,671,213 (1928). The wire runs white-hot; iodine vapour is released. Picture: the patent drawing.