Transient electric light scattering. III. Investigation of the stability of palygorskite colloid solutions

Abstract

The transient light scattering method is used for the preliminary study of the stability of palygorskite colloid solution to which the cationic surface active substance cetyl pyridinium chloride (cpc) was added. The cpc concentration at which the minimum colloid stability was found (10 −5 mole/liter) by the variation of the intensity of the scattered light coincided with the presence of a minimum in the value of the electric polarizability. The parallel electrophoretic measurements showed that at the same concentration the palygorskite particles had a considerable ζ-potential (about −30 mv) and that the isoelectric point was at a cpc concentration of 1.5 × 10 −4 mole/ liter at which the solution was obviously far more stable. The reality of the minimum of the electric polarizability and the difference between the isolectric point and the minimum polarizability points have been discussed and an explanation has been suggested for the correlation of the minimum colloid stability to the minimum electric polarizability point. We hope that this study not only demonstrates the possibilities of the electro-optic methods for the study of the stability of the disperse systems, but also provides important evidence on the probable importance of the dipolar interactions (due to interfacial electric polarizability) for colloid stability.