stage of the reaction in the early stages of a chlorination reaction the silicon tetrachloride concentration in the feed gas is more than the concentration in the effluent gas indicating reaction of silicon tetrachloride with alumina to make aluminum chloride late in the run the situation is reversed thus a higher ratio of silicon tetrachloride to chlorine may be desirable in the later stages of the reaction process to avoid net chlorination of silicon another approach to avoiding net silicon tetrachloride production from the overall reactor system would be to feed relatively greater amounts of silicon tetrachloride early in the reaction in order to convert it to aluminum chloride the present invention makes it possible to operate the chlorination process at maximum efficiency by independently adjusting the proportions of chlorine and silicon tetrachloride in the various stages of the reaction process to illustrate the advantage of horizontally staging a reactor or reactors in accordance with this invention kaolin clay was chlorinated and the mole ratio of alcl 3 to sicl 4 was measured as a function of chlorination time in the chlorination process 0 75 mole of cocl 2 per hour was used as the chlorinating and reducing agent for an agglomerate of kaolin clay and 5 kalcl 4 at 600 u00b0 c and produced the following result __________________________________________________________________________mole ratio alcl sub 3 sicl sub 4 for clay agglomerates mole ratio alcl.