Hydrodynamic processes in dynamic bubble pressure experiments Part 5. The adsorption at the surface of a growing bubble

The dynamics of the adsorption process at the surface of a growing bubble is described for a diffusion-controlled adsorption mechanism. The model is linked with the measuring procedure in maximum bubble pressure experiments as it is programmed in standard tensiometers. As a result the pressure-gas flow rate dependence is obtained which is the basis of the Lauda tensiometer MPT2. The theoretical results allow to define the necessary corrections for calculation procedures used in bubble pressure tensiometry, and to estimate possible experimental errors. Moreover, the importance of particular features of commercial instruments is demonstrated, such as the requirement of a large gas reservoir and a maximum length for capillaries needed to reach short adsorption times of microseconds and below. The influence of the surfactant concentration as studied for decyl dimethyl phosphine oxide on the particular shape of all characteristic dependencies is quantitatively reproduced by the theory. (C) 2001 Elsevier Science B.V. All rights reserved.