Three new techniques for measuring gas dispersion properties: local gas holdup, local gas rate (superficial gas velocity) and bubble size distributions have been developed. Gas dispersion properties were measured in a 50 L lab scale flotation cell, using these techniques. The cell was operated under batch conditions, two-phase system, (gas-liquid). The experimental conditions were modified altering the operating conditions in the cell: impeller speed and gas flow rate. The experiments were conducted at a frother concentration exceeding the critical coalescence concentration. It was found that bubble surface area fluxes measured, were limited to a narrow interval, ranging from 27 to 36 m(2)/m(2) s. The results suggest that bubble surface area fluxes in mechanical cells might be limited to a narrow range of values with a rather low upper limit. This paper includes a detailed description of the new methods, describing their advantages and limitations, it also discusses the outcome of the experiments. (C) 2003 Elsevier Ltd. All rights reserved.