Ytterbium: Oxide Reduced by Lanthanum at 1020 °C in Vacuum, Metal Distilled Off (Shindo and Yagi, US 2010/0260640)

Ytterbium boils far more easily than lanthanum. Heated with lanthanum in a vacuum, ytterbium oxide gives up its oxygen to the lanthanum, and the freed ytterbium leaves as vapour and condenses in a cooler zone, while lanthanum oxide stays behind. Result: ytterbium metal ingots; 20 kg of distillate in the patent's run, low in sodium, potassium and lithium. Source: Y. Shindo and K. Yagi, US patent application 2010/0260640 (2010), Example 1. Not given: how much lanthanum, the vacuum, the time, crucible and condenser materials. Picture drawn by Youblob.