Titanium trichloride violet form

Titanium Trichloride. Titanium trichloride [7705-07-9] exists in four different soHd polymorphs that have been much studied because of the importance of TiCl as a catalyst for the stereospecific polymerization of olefins (120,124). The a-, y-, and 5-forms are all violet and have close-packed layers of chlorines. The titaniums occupy the octahedral interstices between the layers. The three forms differ in the arrangement of the titaniums among the available octahedral sites. In a-TiCl, the chlorine sheets are hexagonaHy close-packed in y-TiCl, they are cubic close-packed. The brown P-form does not have a layer stmcture but, instead, consists of linear strands of titaniums, where each titanium is coordinated by three chlorines that act as a bridge to the next Ti The stmctural parameters are as follows ... 

Titanium trichloride is an extremely easily oxidized material which dissolves in water to form a violet solution. On oxidation, it is converted to the colorless titanic acid, Ti(OH)4. Using a titanium trichloride solution of known strength, it is possible to reduce quantitatively dyes of various classes, the endpoint being taken as the point where the color of the dye disappears. 

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