The invention refers to an apparatus for producing water saturated with air under high pressure and preferably intended for dispersion in flotation plants, which apparatus comprises a preferably standing cylindrical pressure vessel (21) which during operation to a controlled level is partly filled with pressurized water flowing through said vessel and out through an outlet in the lower part of the vessel and partly with continuously added compressed air, whereby during the passage of the water through the vessel (21) air is dissolved in the water. The supply of pressurized water to the apparatus is arranged at the upper part of the pressure vessel (21) by means of a spray-nozzle (24) or similar arrangement which splits the water flow. The spray-nozzle is so designed that at least part of the water flow sprays and essentially covers the inner walls, of the upper, during operation air filled portion, of the vessel (21) by means of a water curtain which portion is supplied with compressed air through a conduit (27) arranged in the wall of the vessel in this portion.