ABSTRACT
In the course of consecutive cycles the situation changes gradually (curves 3 and 3′), and at the 10th cycle (curves 4 and 4′) the kinetic changes and the l2 (τ) dependencies become nonlinear. This leads to the conclusion that in thin capillaries, where the ratio of surface area to unit volume (proportional to 1/r) is high, to obtain reproducible results the capillary surface must be preliminarily set in equilibrium with solution, thus avoiding uncontrollable loss of surfactant during capillary suction. In this regard, in all the following experiments capillaries were equilibrated with each solution under investigation by pumping the solution through the capillary 1-3 h before the experiments. The thinner the capillary, the longer must be the time of formation of an equilibrium adsorption layer on capillary walls. The necessary time of equilibration was estimated on the basis of adsorption capacity of quartz surface, and controlled experimentally [8].
