Thanks Frank, I spent many hours trying to come up with a scheme to do that, and then weigh the sol before and after filtration to determine the percentage of a given size particle in the sol, but gave up for exactly the reasons you state. I also suspect that charge effects may cause small particles to adsorb to the filter medium even if the particles are small enough to pass.
James-Osbourne: Holmes -----Original Message----- From: Frank Key [mailto:[email protected]] Sent: Friday, June 01, 2001 9:14 AM To: [email protected] Subject: Re: CS>Re[2]: CS>Measuring particle concentration of colloids James wrote: > Can you recommend a filter which will pass 10 nm Ag and smaller and stop > larger particles? I know of no such filter. The problem with filters generally is that a filter of a specified pore size, say 1 micro, will soon start to clog and the effective pore size quickly reduces to a small fraction of the original. Far more predictable is the use of centrifugation. Once the parameters are set the process can be done continuously with very predictable results. To get below 10 nm particles does require what is called "ultra centrifugation". Even 20,000 G-forces will leave some particles in the 20-80 nm range, albeit only a few. Unfortunately, the cost of the equipment rises exponentially. frank key -- 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] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
