ABSTRACT
It is well known that the effectiveness of hydrophobed silica-polydimethylsiloxane antifoams in aqueous solutions deteriorates markedly during both use [1-7] and dispersal as an emulsion [6]. Results of Marinova et al. [7] illustrating this effect are reproduced in Figure 6.1. Here the time taken for foam collapse after repeated shake-quiescent cycles of a solution of 0.01 M aerosol OT (sodium bis-octyl sulfosuccinate) containing ~0.1 g dm-3 of hydrophobed silica-polydimethylsiloxane antifoam is plotted against number of cycles. Antifoam was added neat to the solution without predispersal. Marked deactivation of the antifoam is observed after 50-60 cycles.
