If I may interject.... Using the Hach silver chemistry, Bruce found that the digestion process, which involves all sorts of nasty stuff, produced erratic results with CS. This was verified by a Hach tech rep. present at Bruce's lab.
They decided that the process works reliably without the digestion. That is the method which I use to measure mg/L-PPM. I think it is also the method used by Bob Berger. Bob, Bruce, and myself have very close results with the same samples. If someone is doing the Hach test with digestion, can I send you a sample to see how well they correlate. I will reciprocate with your sample if you like. I have yet to get an ISE [R&D funding limitations]. I think the "charge per cluster" theory is probably correct. Has anyone ever discussed this in detail with an ISE manufacturer? James Osbourne Holmes [email protected] -----Original Message----- From: Marshall Dudley [SMTP:[email protected]] Sent: Tuesday, October 12, 1999 9:19 AM To: [email protected] Subject: Re: CS>Graph comparison: ppm & conductivity. Ivan Anderson wrote: > PPM reading was supplied by a silver Ion Selective Electrode. > Water was Purified Water BP and read 1uS before electrolysis. Prior to purchasing our spectrophotometer and silver kit, I check into using a silver ion selective electrode for measuring ppm. I was told that it measures the number of ions (amount of charge) assuming the normal mobility of silver ions, and that silver colloid would not produce a correct measurement due to there typically being less charge on each particle than the number of atoms in the particle, and due to the mobility being different than for one ion. To use it properly one has to digest the silver so that you have silver nitrate first, then use the probe on the residual silver nitrate. This is exactly the same process I have to go through with the spectrophotometer for ppm measurements. I was wanting to verify that you were indeed digesting the colloidal silver before using the probe. If so this is a very interesting set of curves. Thanks, Marshall -- 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]>
