The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76)/1-butanol/isooctane/water (with equal amounts of oil and water in the presence of two nonaqueous polar solvents (NPS), ethylene glycol (EG), and tetraethylene glycol (TEG)), have been constructed at 30 degrees C. Regular fish-tail diagrams were obtained up to psi (weight fraction of EG or TEG in the mixture of polar solvents) equal to 0.5, confirming the establishment of hydrophile-lipophile balance (HLB) of the systems. The maximum solubilization capacity passed through a minimum at psi = 0.2. No HLB was obtained at higher psi. The usual fish-tail diagrams were also obtained in temperature-induced phase mapping at fixed W-l (weight fraction of 1-butanol in total amphiphile). Solubilization capacity and HLB temperature (T-HLB) decreased with increasing psi at a fixed W-1, the effect being more pronounced for TEG than EG. A correlation between HLB temperature (T-HLB) and HLB number (N-HLB) of mixed amphiphiles (Brij-76 + Bu) in pseudo-quaternary systems (in the presence of water and partial substitution of water with both NPS) has been established. The novelty of the work with respect to possible applications has been discussed. (c) 2007 Elsevier Inc. All rights reserved.