Improvements in or relating to the purification of titanium trichloride

Titanium trichloride initially purified by washing with an inert aliphatic, cycloaliphatic or aromatic hydrocarbon, e.g. n-heptane, is further purified by refluxing or agitating with 1-50 mole per cent (based on titanium trichloride) of triphenyl phosphine together with an aliphatic, cycloaliphatic or aromatic hydrocarbon for approximately one hour at a temperature not exceeding 100 DEG C. The precipitate is then suction filtered and washed again with an inert hydrocarbon, e.g. n-heptane. The purified titanium trichloride is subsequently used in conjunction with an organic aluminium compound as a catalyst for a -olefin polymerization.