The principal halides of zirconium are listed in Table 7.6, together with the melting points, vapor-pressure equations, and temperatures at which the vapor pressure of each equals 760 Torr. The tetrahalides sublime without melting at atmospheric pressure, like UF6. The lower halides disproportionate before melting.

The halides of greatest practical importance are ZrF4, as a component of fluozirconates; ZrCL), as the feed material for production of zirconium in the Kroll process; and Zrl4, as feed material in the hot-wire process. These will be discussed later in the chapter.

The heat capacity, enthalpy, heat of formation, and free energy of formation of ZrCU are given in Table 7.7.

The tetrahalides are hydrolyzed to Zr02 by steam. They dissolve in water, forming oxyhalides such as ZrOCl2.