Minimal rotation frequencies of impellers dispersing gas in the whole volume of the liquid mixed with blades places under the disk, have been determined. The influence of the following factors: value of the impeller diameter, angle of inclination of the outer blades, and the kind of liquid used, on the process of dispersion, has been investigated. Results of the measurements have been worked out in the form of criterial relationships. Measurements of the mixing power have been carried out. It has been determined that in the state of complete gas dispersion the approximation of results by the dimensional equation in the form given by Michel and Miller, is possible.