A new method of determining the distribution curve of polydisperse colloidal systems

Abstract

No quantitative method has been developed for the complete determination of the distribution curve of polydisperse systems containing all sizes of particles of colloidal dimensions. Certain of the methods used in the mechanical analysis of soils could, with sufficiently accurate temperature control and refine­ment of detail, enable the distribution curve to be constructed as far down as particles of equivalent diameter 200 mμ , but, owing to the slow rate of settling of such particles in water under gravity, the estimations would take several weeks to carry out. These methods are very ably discussed by F. V. von Hahn in a recent monograph. The special problems of the mechanical analysis of soils have been critically reviewed by M. Köhn. The force acting on particles in suspension can be enormously increased by the use of the centrifuge, which has been developed by Svedberg so successfully that even large molecules, such as those of the proteins, can be made to sediment with appreciable velocity. The range of forces available is therefore ample for the study of polydisperse systems.