in a preferred embodiment of the invention , the dispersion can be discharged by means of a two - substance nozzle , by means of which the dispersion is finely atomized by means of a gas , such as , for example , air . the method according to the invention has the advantage that fine drops can be formed , which results in better nebulization . the fine nebule is required for obtaining a more uniform , more complete coating of the surfaces . this ensures a high activity . moreover , the insecticidal dispersion retains the insecticidal activity . the use of the two - substance nozzle is advantageous because the discharge of a fine nebule by means of a one - substance nozzle entails an unduly high pressure , which destroys the insecticidal dispersion , which thus looses its activity . in particular , the hydrophobicity of the silicic acid is destroyed , making the silicic acid hydrophilic . as a result , the insecticidal activity is lost . in one embodiment of the invention , the aqueous dispersion of the hydrophobic silicic acid can be conveyed to the discharge nozzle by conveying the dispersion in a pipeline and moving the dispersion on within the pipeline by means of a rolling motion . the rolling motion can be carried out by means of a hose pump , hose - type screw pump , peristaltic pump or rotary positive - displacement pump . a peristaltic pump or rotary positive - displacement pump is known from de 197 13 689 or de 197 17 452 . comparison one - substance / two - substance atomization of the insecticidal dispersion with regard to droplet size and mortality ( activity ) a graphic comparison of the droplet size is shown in fig1 .
aqueous dispersions of hydrophobic silicic acid are applied using a two - substance nozzle . the aqueous dispersion is employed as insecticide .