Hi Frank, So that explains why our CS shows very faint Tyndall except in the dark or subdued light. It's because the CS is mostly ionic. By your recent analysis of CS made with our SG7 it's 99.97% ionic.
What wasn't clear to me is why there were some large particles showing in the microphotographs and yet I see a weak Tyndall. That has always bothered me. It was a dichotomy that I couldn't rationalize. Thanks for making it more clear to me. However, there's another problem. We have had samples analyzed using AA and the results always came back 85% ionic...15% colloidal. That seems incongruous doesn't it? How do you think it can be almost 100% ionic when you test it and only 85% when another lab does the test? I'm stumped. Do you think one of the methods skews the results? I have been able to produce CS with very pronounced Tyndall but of course it was always colored....the depth of color directly related to Tyndall effect. I have always tried to produce clear CS knowing the particles were as small as possible if there was no color. Trem ----- Original Message ----- From: "Frank Key" <[email protected]> To: <[email protected]> Sent: Thursday, September 19, 2002 4:22 PM Subject: Re: CS>Buyer Beware > TEM images of ionic silver solutions are virtually worthless for the > following reason: > > When attempting to use a Transmission Electron Microscope(TEM) to observe > colloidal silver solutions, the sample must be desiccated to remove the > water. This removal of water forces the silver ions in solution to combine > with anions in solution to form silver compounds. This dramatically changes > what was in solution so that what is observed using the TEM now has little > relationship to what was in the solution before desiccation. For this > reason, the interpretation of TEM images of ionic solutions becomes > difficult in the extreme (read virtually impossible!). > > The TEM is sometimes used in an attempt to measure the size of particles in > solution. The U.S. National Bureau of Standards (now N.I.S.T) has determined > that it would required at least 10,000 TEM images be analyzed in order to > make a statistically valid measurement of particle size based on TEM images. > For this reason, the TEM is not considered viable for measuring particle > sizes. > > When you try to use a TEM to examine ionic silver solutions, you wind up > only seeing the silver oxide that is formed when the sample is desiccated. > You are not seeing the silver particles because the particles of silver > oxide out number the silver particles by several million to one. Below is an > explanation of what happens. > > What happens to the silver ions in solution when the water is evaporated? > Silver ions in a solution cannot exist without water, so when the water is > evaporated the silver ions (cations) must combine with an available anion to > form a compound. The predominant anions present in a silver colloid solution > are hydroxide and carbonate. The compounds thus formed are silver hydroxide > and silver carbonate. Silver hydroxide is unstable and reduces to silver > oxide and hydrogen. The silver carbonate will reduce to silver oxide and > carbon dioxide. The final compound that remains is silver oxide. > This process begins as a single silver ion is forced to combine with a > single anion forming a single molecule of the compound. The molecule has no > ionic charge and therefore no repulsive force. The lack of repulsion causes > the molecules to be attracted to each other by van der Waals' force of > attraction which causes them to aggregate and form small particles of the > compound. The size of the particle growth is limited by the reduced mobility > of the molecules as the water evaporates. What remains is particles of > silver oxide whose diameter is 1 - 3 nanometers. It is these particles which > predominate in TEM images made of silver colloid solutions which have a high > ionic content. > > frank key > www.colloidalsciencelab.com > > > > > -- > 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: [email protected] > > Silver-list archive: http://escribe.com/health/thesilverlist/index.html > > List maintainer: Mike Devour <[email protected]> > > >
