Protactinium Concentrate: Pitchblende Residues Leached, Fused and Carried Down on Zirconium Phosphate (Agruss, 1935)

A works-scale extraction of protactinium, carried on from I. G. Farben's 1928 process. The residue left after radium has been taken from pitchblende still holds about 300 mg of protactinium oxide per tonne. An acid leach, a caustic-soda fusion and a water leach strip away iron, lead and most of the silica; zirconium phosphate and silica then carry the protactinium down. Result: a concentrate of 4-5 kg per tonne holding 85-90 % of the protactinium at about one part in 5000. In 1935, 1200 kg of residue had given 250 mg of Pa2O5 in this form. Source: M. Agruss, The Technical Extraction of Element 91 - Protoactinium, Industrial and Engineering Chemistry 27 (1935). Unknown: how the residue and the zirconium oxychloride were made. Not given: the final potash melt. The residue is radioactive. Picture drawn by Youblob.