Protactinium: from the Zirconium Phosphate Concentrate (Grosse and Agruss, 1934; Isolation Method Unknown)

How the first weighable protactinium was won. Grosse and Agruss took the zirconium phosphate concentrate from Joachimsthal radium residues and, by laboratory methods, isolated 100 mg of pure protactinium pentoxide from 1200 kg of residue. Result: pure protactinium pentoxide, the first step to the element. This blueprint maps the route; the laboratory steps and the reduction to metal are not described here. Source: M. Agruss, Industrial and Engineering Chemistry 27 (1935), which reports the result and cites Grosse and Agruss, Journal of the American Chemical Society 56 (1934), p. 2200. Unknown: the isolation and the reduction to metal; those papers were not available. Protactinium is radioactive and highly toxic. Picture drawn by Youblob.