Particles In Electrolyte Solution Research Articles

Dielectric loss of colloidal particles in electrolyte solution at microwave frequencies

The dielectric loss of aqueous colloidal suspensions of polystyrene particles have been measured for various KCl and LiCl concentrations at a frequency of 10.0 GHz in the temperature range of 0 to 60°C. The dielectric behavior is characterized by the presence of a remarkable thermal anomaly, strongly affected by the ionic species and their concentrations. The results are analyzed in terms of some “mixture equations” and there are suggestions that the water in the double layer exhibits a dielectric constant different from that of the bulk medium.

The solution of a modified Poisson—Boltzmann equation for colloidal particles in electrolyte solutions

The solution of a modified Poisson-Boltzman (PB) equation for the region between two colloidal particles immersed in a 1-1 electrolyte is investigated for low potentials. The practice familiar in the theory of colloidal stability, of replacing the particles by two infinitely thick parallel plates, is employed. Differences between this study and a similar one by Bell and S. Levine include a more rigorous treatment of the “imaging effect,” an avoidance of the iterative assumption of calculating modifications to the PB equation with classical forms for the potential, electric field and volume densities of the ions and a “constant charge” assumption with respect to adsorbed ions and the charge in the plate. Numerical solution shows that contrary to the latter work, with these changes the modifications can significantly effect the magnitude of the force between two particles.

Comparison of Theoretical Equations for Potential Energy of Electrostatic Repulsion of Colloidal Particles at Constant Surface Charge

Recently, derived and relatively simple expressions for the energy of electrostatic repulsion between flat plates and spheres at constant surface charge were compared with the more rigorous expressions of Jones and Levine and of Müller. They are quantitative of the electrostatic barrier to the collision of colloidal particles in electrolyte solutions within the limitation of small surface potentials, ψo < 25mv. They are also useful in the general approximation of colloidal stability of most practical systems, despite the limitations on the validity of the expression at higher surface potentials.

Observation of Aspherical Particle Rotation in Poiseuille Flow via the Resistance Pulse Technique: I. Application to Human Erythrocytes

The resistance pulse detector (Coulter counter) has been widely applied to the problem of determining the volumes of insulating particles in electrolyte solutions. This technique is based on the simple relationship, DeltaR/R = fv/V, between the fractional resistance change DeltaR/R and the ratio of particle volume v to pore volume V. The proportionality constant f is a function of particle shape and orientation. Direct observation of the expected resistance anisotropies for aspherical particles is reported here. As predicted by simple hydrodynamic theory each individual resistance pulse has a periodically varying amplitude as it traverses a long pore in the shear field of Poiseuille flow. Characteristics of the particle motion allow improved volume distribution determinations by properly accounting for the shape factor. Application is made to normal human erythrocytes and a gaussian volume distribution with a coefficient of variation approximately 19% is found. The electrical shape effect for erythrocytes is consistent with an oblate ellipsoidal particle with a diameter-to-thickness ratio of 4. Analysis of the data indicates that the convergent entrance flow orients the cells so that they enter the pore with their axis of symmetry perpendicular to the pore axis.

Comment on the Article “On the Theory of the Dielectric Dispersion of Spherical Colloidal Particles in Electrolyte Solution”1

Comment on the Article “On the Theory of the Dielectric Dispersion of Spherical Colloidal Particles in Electrolyte Solution”¹

Light scattering by charged particles in electrolyte solutions

AbstractIt is easy to show that the concentrations of the ions in an electrolytic solution do not fluctuate independently. For this reason the theory of fluctuations does not represent an adequate approach to the problem of light scattering by electrolytes.The formulae obtained from distribution functions are discussed. It is assumed in most of the treatment that a colloid particle with its double layer can be regarded as a separate unit. On this basis formulae are developed for compact spherical particles and random coils.