Ivan wrote: > No. The Tyndall Effect is only manifest when the particle is much > smaller than the wavelength of light. For instance, gold colloids look > red when the particles are about 13nm in diameter. > > Regards > Ivan.
That statement is not true. TE intensity of reflected light is maximum when the particle size is one wavelength of the illumination. For a 632 nm laser, the highest intensity of reflected light will be for particles that are 632 nm in diameter. The intensity of the reflected light diminishes as the particle get smaller than the wavelength of the illumination source. Your comment on the color of colloidal gold being red when the particles are about 13 nm is false. Mesogold, a colloidal gold product, is ruby red and has particles that have been measured to be 1.4 nm. The color of a colloid is not solely determined by particle size. It is also influenced by the particle dispersion which is effected by zetapotential. A small ionic change can change the zetapotential and make a sol consisting of the same sized particles to appear as: red, yellow, blue, brown, green, and violet. We have proven this in a lab that is capable of accurate measurement of particle size. At the Colloidal Science Lab we use the Malvern Zetasizer 3000 HSA, which is a photon corellation spectrometer designed to measure colloidal particles in the nanometer range. I would be interested to know how the particle size is being determined by those who are making authoritative sounding statements about particle size properties. . frank key -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: silver-list@eskimo.com Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <mdev...@eskimo.com>
