The Hunter process was the first industrial process to produce pure metallic titanium. It was invented in 1910 by Matthew A. Hunter, a chemist born in New Zealand who worked in the United States. The process involves reducing titanium tetrachloride (TiCl4) with sodium (Na) in a batch reactor with an inert atmosphere at a temperature of 1,000 °C. Diluted hydrochloric acid is then used to leach the salt from the product.
Prior to the Hunter process, all efforts to produce Ti metal afforded highly impure material, often titanium nitride (which resembles a metal). The Hunter process was used until 1993, when it was replaced by the more economical Kroll process, which was developed in the 1940s. In the Kroll process, TiCl4 is reduced by magnesium instead of sodium. Both methods share the same initial step, obtaining TiCl4 from ore by chlorination and carbothermic reduction of the oxygen. The Kroll process is now the most commonly used titanium smelting process.
