Rayleighs formula eq 2 has been applied to the

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Unformatted text preview: t KS involves the refractive indices of the particle and the medium. • Rayleigh's formula (Eq. 2) has been applied to the estimation of particle sizes and therefore to the estimation of molecular weights. • When the particle dime n s i o n s ar e n ot small c o mp ar e d t o t he wa velength, a nd the parti c l e s ar e not spherical, the theory is much more complicated. 3 Less detailed studies can be carried out with an instrume nt known as an ultramicroscope. T his is a useful technique for c ounting p articles in a sol if t he a m o u n t o f m at e rial p resent a s disper se phase is k nown, it i s t hen pos sible t o make an estimate of the size of the particles. Particles detected in an ultramicroscope undergo continuous and rapid motion in all directions, and this is known a s Brownian movement. ELECTRICAL PROPERTIES OF COLLOIDAL SYSTEMS When two electrodes are placed in a sol and an electric potential is applied across them, the particles in general move in one direction or another. This migration of colloidal particles in an electric field is...
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This note was uploaded on 10/25/2012 for the course CHEMISTRY 570.448 taught by Professor Billball during the Fall '10 term at Johns Hopkins.

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