A simple automated method of quantitative characterization of foam behaviour

There are various methods available to measure foam stability. However, their main drawback is that their results are hardly comparable because definite boundary conditions are missing. One particular disadvantage is that there is no method which is applicable to systems of very low (transient or ‘wet’ foams) as well as of very high (metastable or ‘dry’ foams) foam stability. Here, we put forward a novel automatic, pneumatic method that is applicable to both systems. Its principle relies on the measurement of the foam produced by dispersing a definite amount of gas in a definite volume of solution at constant gas velocity. Foam and draining solution are determined simultaneously. This method has advantages over all other methods in several respects such as: (1) it represents a simple and definite procedure under well‐defined boundary conditions, (2) it is generally applicable to all kinds of foam, and (3) it provides new standard parameters for the quantitative characterization of foamability and foam stability. The standard parameters can be related to the basic adsorption properties and the structure of the surfactant. The method's capability is demonstrated with three different non‐ionic and ionic surfactants belonging to the wet (n‐octanoic acid) and dry foam systems (n‐nonyl‐α‐ D ‐glucopyranoside and sodium dodecylsulfate).