PROCESS FOR THE PREPARATION OF SILICON AND COMPOUNDS THEREOF IN A VERY FINELY DIVIDED FORM

Silicon of specified particle form is prepared by reacting silicon with gaseous silicon tetrachloride at high temperatures to give silicon dichloride, which disproportionates at lower temperatures to give silicon of specified particle form and silicon tetrachloride. In order to prepare very finely divided silicon of a particle size of < 1 mu m and a BET surface area of > 10 m /g of pulverulent or bulk silicon at temperatures above 1100 DEG C, the reaction is carried out using silicon tetrachloride in excess and the gaseous reaction mixture is cooled very rapidly down to 900 DEG C and from there without stopping while maintaining a residence time of 5 to 100 seconds down to 600 DEG C, during which the silicon dichloride formed disproportionates to the desired very finely divided silicon and silicon tetrachloride. The silicon thus obtained can be used further for preparing silicon compounds in very finely divided form.