Titanium tetrachloride is the inorganic compound with the formula TiCl₄. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl₄ is an unusual example of a metal halide that is highly volatile. Upon contact with humid air, it forms spectacular opaque clouds of titanium dioxide (TiO₂) and hydrogen chloride (HCl). It is sometimes referred to as "tickle" due to the phonetic resemblance of its molecular formula (TiCl₄) to the word.