The chlorination of crude silicon (~98% purity) by anhydrous hydrogen chloride gas is studied in terms of the effects of temperature, HCl flow rate, silicon particle size and silicon packing height. A fairly wide range of working condition is found which will give the best yield of the desired product trichlorosilane SiHCl3. The results are discussed and compared with some existing data from the works of T.H. Loh  and G. Pauls [2, 3, 4]. An attempt using Cu powder as catalyst is tried but no catalytic effect is observed.