Classical reactor design theory, incorporating the use of the axial dispersion model and assuming flotation to be a first-order process, is shown to be adequate in predicting the performance of a large flotation column, using a rate constant determined in a small column. The vessel dispersion number is accurately predicted using published relationships. It is preferable to determine the small-column rate constant under conditions in which the froth zone recovery is 100%. A froth zone recovery of 25% in the large column was found to be applicable for the present scale-up calculation procedure. If the bubble sizes in the two columns are not the same, it is proposed that the proper value of the rate constant to be used for the large column is found by using the relationship k α d b −1.5.