Introduction group IVB

Group IVB includes following elements: Titanium - [Ti], Zirconium - [Zr], Hafnium - [Hf].

In 1791 William Gregor, a Cornish vicar and amateur chemist, examined sand from the local river Helford. Using a magnet he extracted a black material (now called ilmenite) from which he removed iron by treatment with hydrochloric acid. The residue, which dissolved only with difficulty in concentrated sulfuric acid, was the impure oxide of a new element, and Gregor proceeded to discover the reactions which were to form the basis of the production of virtually all TiO2 up to about 1960.

Four years later the German chemist M. H. Klaproth independently discovered the same oxide (or “earth”), in a sample of ore now known to be rutile, and named the element titanium after the Titans who, in Greek mythology, were the children of Heaven and Earth condemned to live amongst the hidden fires of the earth. Klaproth had previously (1789) isolated the oxide of zirconium from a sample of zircon, ZrSiO4. Various forms of zircon have been known as gemstones since ancient times. Impure samples of the two metals were prepared by J. J. Berzelius (Sweden) in 1824 (Zr) and 1825 (Ti) but samples of high purity were not obtained until much later. M. A. Hunter (USA) reduced TiCl4 with sodium in 1910 to obtain titanium, and A. E. van Arkel and J. H. de Boer (Netherlands) produced zirconium in 1925 by their iodide-decomposition process.

The discovery of hafnium was one of chemistry’s more controversial episodes. In 1911 G. Urbain, the French chemist and authority on “rare earths”, claimed to have isolated the element of atomic number 72 from a sample of rare-earth residues, and named it celtium. With hindsight, and more especially with an understanding of the consequences of H. G. J. Moseley’s and N. Bohr’s work on atomic structure, it now seems very unlikely that element 72 could have been found in the necessary concentrations along with rare earths. But this knowledge was lacking in the early part of the century and, indeed, in 1922 Urbain and A. Dauvillier claimed to have X-ray evidence to support the discovery. However, by that time Niels Bohr had developed his atomic theory and so was confident that element 72 would be a member of Group 4 and was more likely to be found along with zirconium than with the rare earths.

Working in Bohr’s laboratory in Copenhagen in 1922-1923, D. Coster (Netherlands) and G. von Hevesy (Hungary) used Moseley’s method of X-ray spectroscopic analysis to show that element 72 was present in Norwegian zircon, and it was named hafnium (Hufiiu, Latin name for Copenhagen). The separation of hafnium from zirconium was then effected by repeated recrystallizations of the complex fluorides and hafnium metal was obtained by reduction with sodium.