Two flotation models, particle at the liquid-gas interface and particle-bubble aggregate, both based on balance of forces, were used for evaluation of experimental data relating the maximum size of floating particles d(max) and their advancing contact angle. It was noticed, by comparing the experimental and model data, that for a given flotation device and material the maximum size of floating particle d(max) increases with increasing particle hydrophobicity and at the same time the acceleration a, experienced by the d(max) particle at the moment of rupture, decreases with particle hydrophobicity. The acceleration values change with cell dynamics and type of flotation device and are usually not available, therefore empirical apparent cell constants A, which characterize flotation dynamics and relate particle acceleration with advancing contact angle have been proposed instead. The values of A were determined by evaluation of experimental data relating d(max) and advancing (detachment) contact angle for constant: particle density, medium density, surface tension, and flotation cell dynamics. Since A depends on particle density, a tentative formula was proposed to link A with density-independent flotation cell constant A(o). The values of A(o) for selected flotation cells were calculated and presented. Using quartz as an example, it was shown in the paper that a positive advancing contact angle does not guarantee flotation because a prerequisite for flotation is non-zero receding contact angle. (C) 2011 Elsevier Ltd. All rights reserved.