Thorium: Oxide Reduced with Calcium and Calcium Chloride in a Sealed Bomb at 950 °C (Marden and Rentschler, US 1,814,719)

Thorium nitrate is burnt gently to a coarse, heavy thoria, then sealed in an iron bomb with clean calcium cuttings and dry calcium chloride (1 : 3/4 : 1 by weight) and heated to 950 °C. Water and dilute nitric acid wash the lime and salt away, leaving thorium powder. Result: bright thorium metal powder, ready for pressing and sintering. Source: J. W. Marden and H. C. Rentschler (Westinghouse), US patent 1,814,719 (filed 1924), pp. 3-6. Thorium is radioactive; hot calcium and thorium are very reactive. Picture drawn by Youblob.