CS>How many ppm in CS
From: JB
Date: Wed, 12 Jan 2005 22:00:21
http://escribe.com/health/thesilverlist/m76914.html
> How could you explain the following:
> I used 240 ml of distilled water and TDS (total dissolved solids)
> meter to measure number of ppm.
> The reading of ppm before applying the CS generator with about 26V
> from batteries: 2ppm
> After 10 min and stirring the water I read 3 ppm
> After next 10 min the reading was 5 ppm
> Finally after 25 min I had 7 ppm on my meter.
> Can we say that the amount of silver liberated in my distilled
> water was 5ppm?
> Regards
> Jurek
Hi Jurek,
You are correct in subtracting the initial dw reading from the final
result, but it is not clear what correction factor the TDS may
require.
Some TDS meters use a 0.5 or 0.7 correction factor to convert their
measured conductivity in uS to ppm. For example, the Hanna HI9033,
HI9034, HI9039, HI9130, HI933100, and HI9635 use different
conversions. See
http://www.hannainst.com/downloads/instr/hi9033.pdf
Also, you need to let the solution stabilize before taking readings
to allow the ions to reach a uniform distribution throughout the
solution. This can take several hours after the brew is finished.
One method of determining the silver ion concentration is to use the
Faraday equations to calculate how much silver was liberated, then
compare the result with your TDS reading.
Since you are using a constant voltage system, you need to measure
the current at frequent intervals during the brew, say every 10
seconds, and use WPlot to integrate the curve and obtain the average
current over the brew time.
Put this into Mercury along with the volume of dw, and it will
calculate the amount of silver released. In your case, a short brew
time means very litle will be lost in forming oxides and plateout at
the cathode. So the calculation and the TDS reading should match
very well.
You can download Mercury at:
http://archives.math.utk.edu/software/msdos/calculus/mrcry209/.html
Here are the complete conversion factors:
Coulombs = I * Seconds ; total number of Coulombs
CoulombsGram = 107.868 / 96485 ; Coulombs per gram of silver
ElectronsSec = I / 1.60217733e-19 ; electrons per second
Grams = CoulombsGram * I * Seconds ; Faraday's equation
IonsPerNano = IonsSqInSec / 6.45e14 ; ions per square nanometer/sec
IonsSqInSec = ElectronsSec / SquareIn ; ions per sq. in. per sec
Litres = 3.785 * Gallon ; convert gallons to litres
Litres = Millilitres / 1000 ; convert millilitres to litres
Milligrams = Grams * 1000 ; convert grams to milligrams
Millilitres = 29.57 * Ounces ; convert ounce to milliliters
NumberIons = ElectronsSec * Seconds ; number of silver ions
ppm = Milligrams / Litres ; 1 ppm is 1 milligram per litre
ppmPerHr = ppm / Hours ; ppm per hour
Seconds = Hours * 3600 + Minutes * 60 ; get seconds
uASqIn = 1e6 * I / SquareIn ; current density in uA per sq in
You need to add the parameters for your system. Here's the typical
parameters for my Godzilla cs generator:
I = 775e-6 ; current in Amperes
Millilitres = 2000 ; volume of dw
Minutes = 0 ; minutes
ppm = 22 ; target ppm
SquareIn = 11.5 ; wetted area in square inches
A constant current generator will greatly simplify the calculations.
Best of Luck!
Mike Monett
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