Robert F. Steiner

Light Scattering and Spectrophotometry of Colloidal Solutions

During the past several years it has been demonstrated that the light scattered from dilute solutions of macromolecules or colloidal particles is intimately related to the weight, size, and interaction of the solute species. Theoretical developments and improved techniques have made possible the determination of the molecular weight, dimension and activity coefficient of a number of polymers and proteins in solution. In these investigations the intensity of light scattered at various angles from a monochromatic beam passing through the solution has been measured by means of specially designed photometers. However, it would appear that the equivalent information could be derived from a different means of observation—that of transmission measurements at various wave‐lengths. If this possibility could be exploited the common techniques of spectrophotometry could replace the more specialized ones now used. The extent to which this is feasible is explored in this paper.As a first step it is necessary to review...

Macro‐Ions. I. Light Scattering Theory and Experiments with Bovine Serum Albumin

The theory of light scattering is extended to include solutions of macro‐ion salts such as charged proteins and polymeric electrolytes. Equations for the angular intensity distribution are obtained for three types of interaction potential: (1) that of rigid, non‐interacting spheres, (2) an electrostatic potential consistent with the Verwey‐Overbeek theory, and (3) a simple Gaussian‐type repulsion. Because the repulsive forces between the macro‐ions are generally strong and long range, the concentration and angular distribution of the scattering may be very pronounced. Two unique and important extremes exist. If the concentration of the macro‐ion salt is altered without introducing additional electrolytes, the effective diameter of the macro‐ion is inversely proportional to the cube root of the concentration. In this situation the essential features of the scattering are quite novel. First, the reciprocal reduced intensity rises steeply from the intercept at zero concentration, bends over and becomes nearl...