On Celtium and Hafnium

Abstract

IN our letter of February 9, which appeared in NATURE of February 24, p. 252, we have shown that the element hafnium, of atomic number 72, detected by us in zirconium minerals, possesses physical and chemical properties quite different from those ascribed to a rare earth element celtium, the discovery of which was announced by Urbain in 1911, and which recently was believed by Dauvillier and Urbain also to possess the atomic number 72. In a communication of February 19 to the Paris Academy of Sciences (Comptes rendus, vol. 176, p. 496, 1923) Urbain discusses the same problem and still claims the identity of his celtium with our hafnium and by a claim of priority rejects the latter name. In the meantime, through the investigation of Hansen and Werner (see NATURE of March 10, p. 322, and the above letter in this issue) on the optical spectrum of hafnium and on the spectrum ascribed by Urbain to celtium, new data have been brought to light, and we should therefore be glad to take the opportunity to complete our arguments as regards the questions discussed by Urbain.