# silver estimate in fixer



## fonnie (Jul 13, 2014)

Hi all,

I was wondering what method is more accurate at determine the silver contents in fixer.

I've used the copper wire test.
And I've used silver estimator paper.

Both give an estimate, because the copper wire is time-based, and thus a bit difficult to maintain accurate measure.
The estimate paper are colored and the scale is not very accurate. See photo.

Problem is, if you don't know the amount of silver / liter, how can you adjust your zinc powder weight, Or do you calculate your final efficiency?

Are there other way to determine silver contents, an easy way, because I don't have a lab, not chemicals or equipment to do titrations and stuff.

Any thoughts?

Best Regards

Fonnie


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## Westerngs (Jul 13, 2014)

I would take a small sample of fixer, add small increments of zinc, stir, test with bright copper wire. Continue until copper wire test shows no silver. Now you have estimate for zinc needed for whatever volume you have.


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## Palladium (Jul 14, 2014)

He hit the nail on the head. I would do exactly like he said except i would do the whole batch that way instead of just a sample. Each batch would be different so performing the sample test on each one would eat up a lot of time and only give you ball park numbers. In the end you would still have to test for complete reduction using a copper wire. This is where real experience comes into play. The only other way would be proven lab procedures as far as i know.


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## fonnie (Jul 14, 2014)

Westerngs said:


> I would take a small sample of fixer, add small increments of zinc, stir, test with bright copper wire. Continue until copper wire test shows no silver. Now you have estimate for zinc needed for whatever volume you have.



But is the "1 gram of Zinc equals 1 gram of Ag" correct, I've read somewhere that maybe 0.37gram of Zinc would convert 1 gram of zinc?



Palladium said:


> I would do exactly like he said except i would do the whole batch that way instead of just a sample. .



But if you have to, let's say, give a quote to a customer, you would want to be as accurate as possible to not over- or underestimate your profit.

I've been searching myself, and I think chemical analasys is the only accurate thing, the 2 other (copperwire and estimate paper) are indeed giving you Ballpark figures.

Best regards

Fonnie


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## Palladium (Jul 14, 2014)

I know that 1 gram of copper will precipitate about 3.4 grams of silver from a nitrate solution so i'm assuming the same for zinc, but don't quote me on that. Someone with more chemistry background than me can run the calculations.

As far as the silver quote goes you have two choices. One is to run analytical test to determine the silver content and pay the customer up front on this. But remember you probably won't get 100% recovery. Their is less room for error but more capital investment from your pocket and a longer pay out period. The 2nd way is to just toll refine the stuff for a %. That way no matter what the silver content you still make your set profit and you don't have to worry about silver content test and you get paid before anybody does. If the owner of the materials wants one let them be the one to pay for it and adsorb the cost and headache. When they send the materials have them send the results along with it. I have a philosophy in my business model. " What comes out the beaker..... Comes out the beaker " In other words If it's there and recoverable i will get it. It doesn't matter what their test says only the final outcome. I run tests on nothing that comes through my doors. It would take me for ever to test each and every piece. I do segregate and spot checks, but as far as the yields i never really care. I just ballpark what i think it may be and run on experience and skill from there. Yield number in the end is all i calculate for a customer. You would say people would balk at that business model, but for me it has been the cat's meow! 

Keep your business model simple!


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## fonnie (Jul 15, 2014)

thanks Palladium,

keeping the business model simple, that's true.

I imagine that with your skill and expirience, you know that you will get everything recovered.
my problem is more like: I know my electrolysis setup works, and after recovery my fixersolution is depleted from the majority of the silver. But I know there is still silver in the solution, but not enough to confirm by a testpaper. (see chart: either 0gr or 1gr/liter)

Defining how much zinc I would need to recover the remainder is a bit hard.

Maybe I should just go with the 'feeling' and start adding zinc in small increments, until it stops reacting.

Best regards

Fonnie


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## meatheadmerlin (Jan 19, 2017)

I realize this post is a bit old, but here is what I came up with.

It is said that 1g Cu yields 3.4g Ag

Copper and Zinc both commonly have 2 valence electrons.
It takes 1 electron to reduce a Silver ion.

So, 1 mole of Copper will reduce 2 moles of Silver ions.
Ag = 107.87g/mol
Cu = 63.55g/mol
Zn = 65.39g/mol

So this gives a ratio of:
2(107.87)/63.55 OR ABOUT 3.3948
This confirms our 3.4g of Silver yield estimate.

Now, to be pedantic,
1 mole of Zinc will also reduce 2 moles of Silver ions.
So this gives a ratio of:
2(107.87)/63.39 OR ABOUT 3.4034

So, in practice it takes about the same weight of Zinc as Copper,
but 1g of Zinc will actually yield a slightly larger amount of Silver than 1g of Copper.


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## eaglewings35 (Jan 20, 2017)

fonnie said:


> Hi all,
> 
> I was wondering what method is more accurate at determine the silver contents in fixer.
> 
> ...


I just finished a totally saturated 5 gallon bucket of sodium thiosulfate, from green industrial 
x-Ray film, and it yielded 893.1g of silver.
Of course this is speculative. Your saturation point may be different than mine.


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