are mixtures wherein the alkyl groups are linear containing predominantly from 4 to 20 carbon atoms with the c 10 or c 12 being the average alkyl group and only minor or immaterial amounts of c 2 and c 20 groups suitable 34 reactive silicas 34 are water soluble and are sodium salts of silicic acids containing at least an average of one sodium atom per silicon atom examples of suitable reactive silicas include the following sodium metasilicate nasio 3 and na 2 sio 3 9h 2 o sodium orthosilicate na 4 sio 4 and sodium silicate na 2 o xsio 2 wherein x 3 to 5 the amounts of materials which are used are shown in the following table expressed as moles per mole of aluminum alkoxide ______________________________________ silica water______________________________________suitable 0 7 10 3 100preferred 0 9 2 0 30 60______________________________________ expressed as sio sub 2 in conducting the process the water reactive silica compound and aluminum alkoxide are added to a suitable reaction vessel faster reaction is obtained by first adding the water followed by the reactive silica compound and then by the aluminum alkoxide the water can be at room temperature or it can be at the temperature maintained in the next step i e 70 u00b0 to 120 u00b0 c upon.