Terry Chamberlin wrote:
Subject: CS>ppm meters
My question is: Do these ppm meters measure both
colloidal (particulate) and also ionic silver content?
PPM meters don't measure silver at all, they measure electrical
conductivity.
Conductivity can be used to approximate the ionic content assuming no other
cations or anions are present. The particles will not contribute to
conductivity.
Use of conductivity measurements can produce wildly erratic results when
trying to determine silver content because the presence of any ionic
species, such as nitrate, carbonate, or chloride will increase the
conductivity.
I had a sample of some silver tested once by Bob
Berger, who reported 12.3 ppm. I had the same CS
tested by a local laboratory that is paid to do
industrial testing, and they found it to be 5 ppm. I
asked Bob about this, and he said they only tested
particulate, not ionic.
Any thoughts on this?
The most common method used by commercial labs for testing silver
concentration are:
1. Atomic absorption spectroscopy (also called an AA or flame AA)
2. Atomic emission spectroscopy (also called an ICP or ICP/AES or
ICP/OES)
3. Mass spectroscopy (also called ICP/MS)
All of these methods would measure the total silver content which include
both the ions and the particles.
Bob Berger uses a spectrophotometer which makes colorimetric type
measurements. A spectrophotometer/colorimetric method only measures the
ionic content unless a process called digestion is used to convert the
particle into ionic silver, in which case the colorimetric method will
measure total silver content (ions + particles). No commercial lab would use
this method today.
Frank Key
Colloidal Science Lab.
www.colloidalsciencelab.com
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