HAFNIUM is the name given by its Danish discoverers (D. Coster and G. von Hevesy) to a metallic element which always occurs in close association with zirconium; symbol Hf, atomic number 72, atomic weight 178.6. The chemists, G. Urbain and A. Dauvillier, on the grounds of an indication of the element obtained by the former, claim the privilege of naming it Celtium, and references to this discussion are given under that heading. The high melting point and electronic emissivity of hafnium are the reasons for the recent issuance of two patents for its use in lamp filaments, particularly in radio tubes.
The properties of this element and its compounds are so similar to those of zirconium and its compounds that separation of the two is a matter of great difficulty, and its discovery has made necessary the revision and correction of all existing data on zir conium because all salts of zirconium are contaminated with from r% to 5% of hafnium.
See J. H. de Boer, Z. Anorg. Chem., 15o, p. (1926) ; von Hevesy, Das Element Hafnium (Berlin, ; O. Honigschmidt and E. Zintl Berichte, P. 453 (1925).