Theoretically yes. Practically, maybe not. If you can get a valid
measurement then you could still be off by what has deposited on the
container sides and bottom, and plated out on the cathode. You could
weigh both electrodees to eliminate the plating out on the cathode. But
you will be looking for a very small amount, if you put 10 ppm of
silver in one liter of water, that would work out to only 10 milligrams
of silver, or .01 grams of silver. Now there are balances that can
weigh that, but when you are looking for a change that small with the
electrodes weighting 10 grams or so, you need an accuracy AND
repeatability of 1 part per thousand or so on the scale, whereas just
weighting it the accuracy could be 1 in 100 and be fine.
With that said, the following might work, even by weighting the electrodes:
http://www.affordablescales.com/scales_specs.asp?specs=558&Acculab_VIC-123
http://www.affordablescales.com/scales_specs.asp?specs=4548&Veritas_S123
Marshall
poast wrote:
Hello Marshall,
Is is possible to weigh the anode before and after and get an idea of how
much is in the solution?
Once again we are looking at very small measurements, but if you did several
batches between weighing, you may get an agerage.
The may be opptimistic, but could give a ballpark esimation.
Tom
----- Original Message -----
From: "Marshall Dudley" <[email protected]>
To: <[email protected]>
Sent: Tuesday, February 23, 2010 8:58 AM
Subject: Re: CS>Which layer of skin for silver deposit?
Doing quantitative analysis for silver compounds is really rather easy,
if you have much silver present. The biggest problem is that at 5-20
ppm, the quantities are so small, that getting a good weight on them is
difficult. It can be done though with a good balance, forget a postage
scale. These pages might give you some ideas:
http://dwb4.unl.edu/chemistry/smallscale/SS063c.html
http://dwb4.unl.edu/chemistry/picts/SS063All.gif
Anyway, this can be done.
Add a few drops of hydrochloric acid (muriatic acid should be ok) to the
mix. Verify that it becomes cloudy. Let the cloudy part settle, and
decant off the liquid. Dry the power and weight. Take the weight in
grams and divide by 1.33, that will give you the silver content of the
precipitant. Now divide that by the amount of water you had in liters
and multiply by 1,000,000. Add .6 ppm for the dissolved portion, and you
will now know the amount of ionic silver in ppm in the mixture.
Now take the same amount of EIS and boil it dry. Add about 10 drops of
nitric acid (this must be done in a test tube) and reflux the sides
while boiling dry again over a flame (or use a flask over a hot plate).
You now have 100% silver nitrate. Weight this in grams and divide by
1.575 and that will give you the total silver content. Divide that by
the amount of water in liters and multiply by 1,000,000 to get the ppm
of silver.
Warning, nitric acid is very very toxic, breathing the fumes will
liquefy your lungs so boiling it must be done under a fume hood. Don't
even think of using a venta hood over a stove, it will completely eat
the metal of the hood and the metal piping to the outside up (if it even
goes outside). Fumes are not only toxic, but will destroy any
electronics you have in area.
Another way to get the total silver would be to add the hydrochloric
acid as above, and boil it dry. Then subtract the amount you got in
grams in the first part. What remains will be the silver content of the
colloidal part. Divide this by the amount of water in liters and
multiply 1,000,000 for the colloidal part in ppm.
PS, if you measure everything in micrograms instead of grams, you do not
have to multiply by 1,000,000 to get the ppm.
Marshall
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