text: Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide.  is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide () and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4", as a phonetic representation of the symbols of its molecular formula ().
  Properties and structure
  is a dense, colourless liquid, although crude samples may be yellow or even red-brown. It is one of the rare transition metal halides that is a liquid at room temperature,  being another example. This property reflects the fact that molecules of  weakly self-associate. Most metal chlorides are polymers, wherein the chloride atoms bridge between the metals. Its melting point is similar to that of .