In an attempt to explore the nature and structure of colloidal liquid aphrons (CLA), the formation and stability of CLA composed of polyoxyethylene 3 dodecyl ether (AEO-3)/n-decane/sodium dodecyl sulphate (SDS)/water were investigated using the conductivity technique and microscopic observations. The formation mechanism and the stability behavior of CLA were derived from the conductivity profiles and verified by the optical micrographs. It was found that the formation was a low-energy emulsification process including a foaming stage and then the exchange of the gas for oil phase. No phase inversion took place during the whole formation process, hence the CLA represented O/W emulsion type. The stability behavior determined by conductivity analysis was described using linear equation at 303.15 K. As the temperature is above 318.15 K, the conductivity profiles of CLA, which presents a different kinetics from the first order model, conformed to the sigmoidal equation σ_t=(σ₁－σ₂)/[1＋e^(t－t₀)/S] ＋σ₂, where σ_t refers to the conductivity at time t, σ₁ and σ₂ refer to the minimum and maximum conductivity during storage, respectively, t₀ is the time for conductivity to reach the value of 1/2(σ₁＋σ₂), and S is the parameter to describe the steepness of the curves. A new mechanism for CLA breakdown was proposed from analyses of the conductivity curves, which involves the simultaneous occurrence of flocculation and coalescence during CLA breakdown process. The coalescence displays two distinct stages including film drainage and film rupture driven by two independent mechanisms, respectively.

Key words: colloidal liquid aphrons, formation, stability, electrical conductivity, optical microscopy