Marshall wrote in reply to a post by me: > > This is confirmed by many scientific references. Go to the library and read > the "Colloidal Chemistry" reference book, it is probably one of the easiest > to find, but I have found at least 8 references that state the same thing, > some textbooks, and others in scientific journals. > Marshall, thanks for the advice, but I have already spent long hours at the university science library studying colloid chemistry and modern colloid chemistry. The fact that particle size influences colour is not disputed by me, as previous posts will testify. What I am disputing is that a silver colloid at a concentration above 5 ppm does not have more particles, but the same number of particles of a larger size, a point you did not address in your reply.
> > Then how can my small DC units produce clear CS at 20ppm and higher as > > measured by the Ion Selective Electrode method? > > Don't know. What is the Ion Selective Electrode method? Send me some of > your clear 20 ppm and I will do a ppm test on it. In no case have I ever > found it possible to exceed 5 ppm by much wihout getting some color. We use > a $5300 machine purchased specifically to test the ppm of silver, and it is > accurate to about 1 part per thousand. If you have found a way to exceed > this level and maintain small particle size I would sure like to know how > you do it. > The fact remains, that I and others produce water clear silver sols at much higher concentrations than you would allow, which means more particles of a similar size surely. The difference between a 5 ppm sol (0.0005% by weight) and a 20 ppm sol (0.002%) is actually quite small and I suspect it is the generating parameters not the concentration that determines the particle size. There are reasons for this which I don't fully understand, but which involve zeta potential, silver 'crystal' configuration, electrode current density, etc. The Ion Selective Electrode method is probably the only way to measure the the ionic concentration of a colloid. The silver ISE is specific to silver and will measure nothing else. It will measure concentrations from 0.01 - 107,900 ppm directly. All other methods, except for chemical (as far as I know) measure total silver content, that is elemental silver and ionic silver. My results have excellent correlation to those of the accredited lab I have contracted to independently test my product, using the Atomic Absorption (AA) method. Whilst I envy you, your expensive uv/vis spectrophotometer and computer interface, I have built essentially the same thing using a programmble RGB led and photodiode for the grand price of NZ$200. I do not therefore feel the need to accept your kind offer to test the results of my small generators, especially as I am based in Auckland, New Zealand. Regards - Ivan -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] List maintainer: Mike Devour <[email protected]>
