A couple of comments Trem, in your text.
James Osbourne Holmes
a...@trail.com
-----Original Message-----
From: Trem Williams [SMTP:t...@silvergen.com]
Sent: Friday, November 12, 1999 10:20 AM
To: silver-list@eskimo.com
Subject: Re: CS>Spectrophotometer, atomic absorption and colorimeter
testing for PPM
Hi Mike,
Here's something else to throw us off. I just had several samples measured
for PPM by a lab using the atomic absorption process. I asked them if they
digested the CS before running the test. Answer was "yes". I asked them
to
run the test on each sample two times; once with and once without
digestion.
I did this because another lab had done the same tests for me without using
digestion. I was interested in seeing what differences would be uncovered.
Well, the results were strikingly different. With digestion (and by that I
mean boiling in aqua regia) the PPM in 16 ounces of water using constant
current production was about 3.5 PPM per hour. The highest reading sample
was 35 PPM after running the generator for 10 hours and the reading for 5
hours was 18 PPM. Pretty straightforward I thought but then the undigested
samples threw me off. They were 19 PPM for the 10 hour run and 11 PPM for
the 5 hour run. These readings were still proportionate to time but only
about 54-58% of the digested readings. The chemist told me that you cannot
get accurate readings without complete digestion. I wonder how many of
those using spectrophotometers, such as "Ole Bob" digest their samples. He
told me once that he bleached the samples but didn't mention digestion.
: Bob is just bleaching the "blank" used to calibrate the meter to 100%
transmission.
Since I really don't know that much about the process, I can't speak with
much authority but I suspect that those using spectrophotometers would also
get much different readings between digesting and not digesting their
samples. I'd be interested in hearing reports from those who have them if
they could run the tests both ways.
JOH: Bruce Marx actually had a Hach guy in his lab. They finally
determined that test to be reliable without the heavy duty hot acid and
unreliable with it. If you send me a sample tested both ways, I will test
it ---in confidence to you only---with the Hach set without digestion, for
comparison.
As a side note, I tried a Hanna instrument silver colorimeter and was
disappointed. One used 4 different chemicals to react with the sample and
the blank and then measured the color difference. When I ran the unit to
test undigested CS, the reading was always zero PPM. In order to see if
the
unit was operable, I dissolved 1 mg silver in nitric acid by boiling and
then added it to enough distilled water to get a 1 PPM standard solution.
When I tested this sample, the unit did give a reading but it was very low
(about 30% of the actual PPM). I sent the unit back because it was not
working accurately enough with my home made standard and didn't work at all
with the undigested CS.
JOH: When you have only one clock you think you know the time.
Afterward, I was told by the lab that did my last tests that digestion in
nitric is not good enough. One should use aqua regia for complete
digestion. So the upshot of all this to me was that you have to digest
completely to get an accurate reading of the total amount of silver in the
dispersion. It is possible I could have gotten better results from the
Hanna unit if I had used aqua regia but I didn't know it at the time.
There is so much controversy about this I am beginning to think there's
some
voodoo involved in getting accuracy.
JOH: See http://borderlands.com/journal/lunar.htm
Thanks for all of your work and sharing the data.
Back to youse guys.
Trem
t...@silvergen.com
----- Original Message -----
From: M. G. Devour <mdev...@mail.id.net>
To: <silver-list@eskimo.com>
Sent: Friday, November 12, 1999 3:33 AM
Subject: RE: CS>wet chem
> > why not shop the net for a used
> > spectrophotometer? I have seen several which will do the trick for
> > about 400. You can get excellent really high-end but obsolete stuff
> > for a bit more.
>
> Just curious: what kind of capability does this kind of spec have?
> What range of wavelengths, UV, visible? Is wavelength fixed, manually
> selected, scanned? Computer interface?
>
> What other parameters are important in evaluating the quality of such
> an instrument? Sensitivity? Resolution?
>
> If I understand correctly, you use the hach reagents to digest and
> mark the silver, then read the absorption on the spec. This is at a
> fixed set of wavelengths, one wavelength, ... or what? Essentially
> colorimitry?
>
> I'm looking for an overview, just so I understand how the pieces fit
> a little better. If an investment of a grand would give me the
> ability to do what I want to do, it'd be just worth thinking about.
>
> > I have just begun recording mS of my batches to plot against
> > analyzed mg/L, more out of curiosity than anything else. Bruce Marx
> > told me a couple of years ago that he had very poor correlation.
>
> Yeah, who knows with the hvac product? You could have such dependency
> on water quality or other seemingly minor variables that it might not
> work *because of the nature of the product*. But for a narrow range
> of process conditions, Ivan is showing us a decent correlation
> between ppm and conductivity in at least his lvdc process. .
>
> > And, knowing PPM, even with precision, is not very helpful in terms
> > of effectiveness it you don't know anything about particle size.
>
> Which is one thing Marshall, I think, told us: there is a correlation
> between absorption vs. wavelength vs. particle size. Which is why it
> would be useful to have a scanning, or scannable, spectrophotometer
> sensitive enough to directly detect the absoption characteristics of
> samples of CS.
>
> > We are also into the realm of how many Angels can dance on the head
> > of a pin: how many silver bits does it take to destroy [Can't kill
> > 'em; my microbiology text says they aren't alive] one herpes
> > simplex viron? Will a huge clump with a big charge do it, or is a
> > single atom best?
>
> Well, if we can at least know the physical characteristics of what
> we're making, we can then attempt to evaluate performance on the
> basis of effectiveness, absorption, excretion, etc.
>
> One step at a time.
>
> Be well,
>
> Mike D.
>
> [Mike Devour, Citizen, Patriot, Libertarian]
> [mdev...@mail.id.net ]
> [Speaking only for myself... ]
>
>
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