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The double-layer interaction energy between two colloidal particles at large separations is proportional to the product of the scaled effective surface potentials of the respective particles (Bell et al., J. Colloid Interface Sci. 33, 335 (1970); Brenner, S. L., and Parsegian, V. A., Biophys. J. 14, 327 (1974)). The exact expression is obtained for the scaled effective surface potential of a plate in a solution of general electrolytes, which agrees with Wilemski's results (J. Colloid Interface Sci. 88, 111 (1982)). An accurate approximate analytic expression is derived for the scaled effective surface potential of a sphere in a solution of general electrolytes. For the special case of a sphere in a symmetrical electrolyte solution, the obtained expression reduces to that derived previously (Ohshima et al., J. Colloid Interface Sci. 90, 17 (1982)). The obtained expressions are found to be excellent approximations to the exact numerical values given by Loeb et al. ("The Electrical Double Layer Around a Spherical Colloidal Particle." MIT Press, Cambridge, MA, 1961), the relative error being less than 1% for κa > 1 (a = sphere radius and κ = Debye-Huckel parameter) at all values of the surface potential.

A survey is given presenting the method of the oscillating bubble. This method provides the opportunity to measure the dilational elasticity of a surface for medium rates of surface area changes of dilation. The results obtained with three surfactant solutions show good agreement with the theory. The critical domain of the measurements, i.e., the dependence of the effective surface elasticity on the frequency, is discussed. The greatest deviations from the theory occur at high concentrations. Here, the establishment of equilibrium between surface and subsurface is obviously retarded.

We have synthesized surface modified ZnS nanoparticles of size 2-3 nm using non-ionic surfactant-stabilized reverse emulsions. The non-ionic surfactants in the Span series, i.e. sorbitan monolaurate (Span 20) and sorbitan monooleate (Span 80) of hydrophilic-lipophilic balance (HLB) values of 8.6 and 4.3, respectively, have been used for the stabilization of emulsions. The role of these surfactants in controlling the size and properties of the ZnS nanoparticles has been discussed. The triethylamine (TEA) has been proved to be the effective surface modifying (capping) agent for the preparation of free-standing ZnS nanoparticles. The Span 20 with the higher HLB value of 8.6 has been found to be highly suitable in synthesizing TEA-capped ZnS nanoparticles of smaller size and higher photophysical characteristics compared to that of the Span 80 of lower HLB value of 4.3. A mechanism for the formation of TEA-capped ZnS nanoparticles from the surfactant-stabilized reverse emulsions has been proposed.

Internal Reflection Spectroscopy, IRS, provides a powerful technique for the in situ investigation and characterization of the functional layers of an adhesive tape. An adhesive tape is a multicomponent system comprised of several functional layers, each layer being a single polymer or a mixture of polymers, sometimes blended with mineral components. The internal reflection techniques applied to tapes may also be extended to the analysis of similar types of polymers and polymer blends. To optimize the spectral information obtained using multiple internal reflection techniques, careful consideration must be given to the internal reflection equipment, particularly the internal reflection element, IRE, or sampling plate. Guidelines for sampling and finding effective surface areas as well as most sensitive IRE regions are presented for some commercially available instrumentation. Some applications of IRS to adhesive tape analysis are presented, including qualitative identification of tape components using limited sample, fingerprinting of tape layers for storage and retrieval, reactivity studies of curing tape layers, migration studies, and identification of surface contaminants which alter the intended function of tape layers.

The frequently neglected correction for statistical bias in the measurement of bubble size distribution at a surface is found to be significant for the size distributions involved in the foaming experiments, insofar as calculation of effective surface viscosity from the drainage theory that was developed earlier by the authors' group is concerned. However, with the establishment of an appropriate surface viscosity, the scatter in predicting the steady rate of foam overflow or drainage by the said theory is barely affected.