Place the "QUSO" F 22 in a container and wet the silica with two-thieds volume of the water. Add the titanium dioxide and benzocaine and transfer to a Waring Blender; agitate for one minute. Disperse the "Brij" 30 in purified water containing the sorbic acid and add to the suspension. Make the solution up to volume and agitate for one minute in the blender.