Coalescence frequency and lifetimes of thin aqueous films formed between nitrogen bubbles were measured in dilute solutions of sodium lauryl sulfate, n-amyl alcohol, and 1-butanol. The bubble pairs were formed on two adjacent capillary tubes by use of a microprocessor-controlled stepping motor, and the coalescence time was determined by an optical sensing method.
For low-molecular weight alcohols such as 1-butanol and n-amyl alcohol, the transition concentration decreased with increase of bubbling frequency. But for high-molecular weight surfactants such as sodium lauryl sulfate, it increased with bubbling frequency. Coalescence times increased with solute concentration and also with surface tension gradient.