Hello Dick, uS is micro siemens, and is a measure of the conductivity of water. Since the electrodes are spaced 1 cm apart the results come out in uS/cm.
Some instruments are set up to display PPM. They do this by measuring the conductivity of a salt solution, then multiplying it by a factor number to arrive at PPM. If you are measuring the same salt concentration that the meter was set up for, you will get reasonably accurate PPM results. Unfortunately, none of the standard calibration solutions are set up for EIS. Trem (SilverGen) made several batches of EIS, tested them with a uS meter, then sent them off for laboratory analysis. He uses a Hanna PWT meter. Since EIS is mostly ionic, and since the PWT meter mostly responds to ions rather than particles, the theory is that the uS value should be close to the actual PPM of silver in the solution once correction factors are applied. The process involves measuring the water you are starting with. When your batch is finished, let it sit for a day or so, then measure it and subtract the initial reading you got for your water. This should be an indicator of the ions in the solution. When Trem got the lab sample reports, he discovered that a "typical" batch has about 85% ions and 15% particles. He suggests using a 1.2 correction factor for EIS made with his generators. While fine in theory, there is some controversy over this. Ode has also had lab samples done, and does not find the correction factor valid. On top of that, the lab people say that a conductivity measurement will only provide a "ball park" estimate of the concentration of silver in solution, and the only way to know for sure is to spend the $200/sample and have it analyzed. This is why I gave my results in uS/cm rather than PPM. The main question is to determine what ion contamination can be introduced into the solution when you heat it up. If there is no contamination being introduced, then it is reasonable to believe the concentration is being increased by removing water from it. Tom ----- Original Message ----- From: "Richard Goodwin" <[email protected]> To: <[email protected]> Sent: Saturday, February 20, 2010 7:23 AM Subject: Re: CS>Which layer of skin for silver deposit? > Interesting... > > How does the unit uS compare with PPM? > > I have two meters, one of which measures PPM, and the other uS, and they show very diferent readings on the same stuff. I don't know if that is because the units of measurement are that different, or because one of the meters is very inaccurate... > > Dick -- The Silver List is a moderated forum for discussing Colloidal Silver. Rules and Instructions: http://www.silverlist.org Unsubscribe: <mailto:[email protected]?subject=unsubscribe> Archives: http://www.mail-archive.com/[email protected]/maillist.html Off-Topic discussions: <mailto:[email protected]> List Owner: Mike Devour <mailto:[email protected]>
