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The detailed study of the evolution of angular positions of the first extrema in the intensity scattered by micrometer-sized spheres is extended to the case of spheroidal particles. It is shown that any spheroid in any orientation behaves as the sphere whose diameter is equal to the maximum thickness of the particle along the direction of the incident wave. Reference is also made to the classical approximations. Likewise we bring to light the relation between the extrema of the Cext coefficient and the occurrence of jumps in the angular positions of the extrema of the scattered intensity.

A geometrical model for water-swollen nonionic micelles in decane is proposed in relation to small angle neutron scattering data. It states that the aggregation number of these lamellar particles is monitored by the hydration degree of the oxyethylene (EO) groups along the polyoxyethylene chains: when hydrated, a EO group must be surrounded by a constant given number of water molecules.

From investigations of ternary systems with nonionic polyoxyethylene glycol alkyl ethers, brine, and alcanes, a classification of the oil-water solubilization properties of these surfactants can be made in terms of the evolution of the whole of the ternary diagrams. A simple relation between the different parameters characterizing the systems is proposed which uses the concepts of the equivalence between temperature and other parameters (HLB, alcane carbon number, salinity).

Two different experimental arrangements of light scattering by flow-oriented spheroids are proposed to show how the optical and morphological parameters of the scatterers can be obtained. The surprisingly good validity of the R.G.D. approximation is also demonstrated by comparison of approximate and exact numerical results. Application is made to the problem of the size dependence of the flow form birefringence.

The surface activity of a new series of nonionic fluorinated surfactants has been investigated in aqueous solution. These surfactant molecules contain both the oxyethylene and the thioethylene groups. From surface tension measurements, the area per polar head and the critical concentration C 1 have been calculated. The data indicate that the fluorocarbon chains are very densely packed perpendicularly to the air/water interface and that the presence of one inserted SC 2 H 4 group in the hydrophilic chain cancels out the effect of two oxyethylene groups. The effective hydrophobicity of these compounds has been compared to that of hydrogenated C m E n surfactants.