specifically according to the process of the present invention the compounds i or the compounds i and compounds ii occasionally referred to overall as 34 silicon compounds 34 hereinbelow are reacted with ammonia under the specified conditions followed by the heat decomposition i e the calcination in these processes for instance when chloroalkyl silanes are used as compound i a relatively small si c range such as 0 5 to 2 is desirably used because the alkyl group in the compound i is readily decomposed in the calcination step contrary to this for instance when chloroalkyl silanes are used as compound i a relatively large si c ratio range such as 1 to 50 is desirably used because the aryl group contained in the compound i is not easily decomposed in the calcination step the reaction of the silicon compounds with ammonia can be carried out either in a liquid phase or a vapor phase it should be noted that although amines may be used in place of the ammonia the use of amines is undesirable in practice because the removal and recovery operations of the unreacted amines are troublesome when the reaction of the silicon compounds with ammonia is carried out in a liquid phase the silicon compounds are dissolved in an organic solvent and brought into contact with liquid or gaseous ammonia to react therewith the organic solvents suitable for use in the above mentioned reaction are those which do not react with the silicon compounds and the ammonia and also which.