Zirconium perchlorate as cold as possible. Zirconium perchlorate is very hydroscopic forming hydrates, and it is hydrolysed by water to yield zirconyl perchlorate, ZrO(ClO). Zirconium perchlorate reacts with vaseline, methyl nitrate or acetonitrile. Zirconium perchlorate is inert towards carbon tetrachloride, chloroform, and dimethylformamide. Zirconium perchlorate reacts with benzene at 20°C, but at -10°C crystals of Zr(ClO)•CH are deposited. Zirconium perchlorate has solid state transition around 45°C, a melting point between 95.5 and 96.0°C and a decomposition point starting around 120°C. The zirconyl perchlorate formed in the heat decomposition, itself decomposes around 290°C to form zirconia, chlorine and oxygen. In the gas phase
Group 4 element to which Coster and Hevesy were guided by Bohr's prediction that hafnium would be a transition metal rather than a rare earth element. While titanium and zirconium, as relatively abundant elements, were discovered in the late 18th century, it took until 1923 for hafnium to be identified. This was only partly due to hafnium's relative scarcity. The chemical similarity between zirconium and hafnium made a separation difficult and, without knowing what to look for, hafnium was left undiscovered, although all samples of zirconium, and all of its compounds, used by chemists for over two centuries contained significant amounts of hafnium.