Abstract
The current status of the experimental and theoretical study on tonic solutions is reviewed. The small-angle X-ray scattering (SAXS) curves on tonic solutes such as proteins, polynucleotides, synthetic macroions, surfactant micelles and so on, show a single, broad peak, which suggests intermolecular ordering of the macroions in solutions caused by an electrostatic attractive interaction These information is confirmed by investigation on a model system, namely on polymer latex particles, which can be studied by naked eyes with an optical microscope. The micrographs provide a visible evidence for the interparticle attraction. The distortion of the ordered structure is fairly large and is a reason of the non-existence of higher order peaks in SAXS curves. The nature of the attraction, which clearly shows the invalidity of the DLVO theory on colloidal stability., is discussed in terms of a recent theory.
