# How do you determine the purity of a silver bar?



## ssharktu17 (Dec 12, 2021)

Say you have a 1000 ounce silver bar how do you test it for purity?


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## Lino1406 (Dec 12, 2021)

XRF should do


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## ssharktu17 (Dec 12, 2021)

Lino1406 said:


> XRF should do


Does it get through plating?


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## Lino1406 (Dec 12, 2021)

If you drill to get inside, yes


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## ssharktu17 (Dec 12, 2021)

Lino1406 said:


> If you drill to get inside, yes


Ah I see so you drill a sample then use the XRF. Is this those handheld ones? I’m guessing they can test through normal plating?


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## orvi (Dec 12, 2021)

ssharktu17 said:


> Ah I see so you drill a sample then use the XRF. Is this those handheld ones? I’m guessing they can test through normal plating?


it depends on thickness of plating. but accurate analysis is always done by drilling few holes with various depth, and then melting the turnings, or just crushing them, homogenizing and measuring directly with XRF.
yes, handheld one is sufficient, if the proper calibration and library is in place. unless that, wild results could be obtained  
point is, that metal content in the ingot is not always the same on the top/bottom part as result of quicker/slower cooling. metal impurities could possibly come out of the melt first or last, so they could end up on the surface, in the middle... and just reading from one place of the bar is often misleading.


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## ssharktu17 (Dec 12, 2021)

orvi said:


> it depends on thickness of plating. but accurate analysis is always done by drilling few holes with various depth, and then melting the turnings, or just crushing them, homogenizing and measuring directly with XRF.
> yes, handheld one is sufficient, if the proper calibration and library is in place. unless that, wild results could be obtained
> point is, that metal content in the ingot is not always the same on the top/bottom part as result of quicker/slower cooling. metal impurities could possibly come out of the melt first or last, so they could end up on the surface, in the middle... and just reading from one place of the bar is often misleading.


Thanks! Thats what I suspecting and the XRF guns are pretty expensive. Are they any cheaper chemical methods to determine percent purity?


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## nickvc (Dec 12, 2021)

If you have a thousand ounce bar I’m guessing it’s stamped, if so it will have a unique reference number that can be checked with its producer for authenticity .


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## orvi (Dec 12, 2021)

ssharktu17 said:


> Thanks! Thats what I suspecting and the XRF guns are pretty expensive. Are they any cheaper chemical methods to determine percent purity?


Gravimetric analysis could work to some extent, but results are solely dependent on "competence" of the chemist. Very rough way of determining silver is dissolving known ammount of metal (say 10g) in nitric acid and then precipitating silver chloride (or any suitable salt of silver). Good wash with dH2O, drying and weighing. As I said, very dependent on how the analysis is done. 
You can alternatively cupell the known ammount of metal to roughly know the content of base metals, but this wouldn´t tell you anything about possible Pd/Au presence.


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## Lou (Dec 12, 2021)

Remelt it and pull a sample from the melt.

Dissolve in nitric acid redistilled nitric acid. If the acid is colorless after boiling and free of sediment, then it is probably pure silver.
Usually copper is the principal contaminant, so an aliquot can be taken out of that solution and neutralized with ammonia until silver oxide precipitates. Keep adding ammonia and if a blue color forms, there is copper contaminating. One must be sure to acidify such solutions after their creation to prevent unwanted possibly explosive compounds forming.


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## Lou (Dec 12, 2021)

Also,

the Volhard method detailed here on the forum would work very well too.


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## Lino1406 (Dec 13, 2021)

Lou said:


> Also,
> 
> the Volhard method detailed here on the forum would work very well too.


If you consider acidifying do it with HCl, never with acetic acid


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## Ray Levi (Dec 14, 2021)

ssharktu17 said:


> Say you have a 1000 ounce silver bar how do you test it for purity?











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## pajarazzi (Dec 14, 2021)

If you have in hand a large scale you can do a Specific Gravity Test Is Cheap and non-invasive, here is the general idea of the procedure: 

The value has to be close to 10.49 for 999 silver, If you are buying it always is wise to do different kinds of tests (XRF, Electroconductive, Chemical, etc)


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## ssharktu17 (Dec 14, 2021)

Thanks I should clarify I am looking to determine absolute purity like .999 vs .9999


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## Lou (Dec 14, 2021)

ICP-OES.


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## Elemental (Dec 14, 2021)

Inductively coupled plasma - optical emission spectrometry at UVA

Inductively Coupled Plasma Optical Emission Spectroscopy​The lab has a Thermo iCap 6200 ICP-OES. The ICP is used for trace composition analysis of many types of samples. Nearly any sample that can be dissolved in liquid (often water, a solvent, or acid) can be run through the ICP to determine the exact amounts of elements present down to the parts-per-billion (ppb) range. The ICP is used to analyze corrosion and oxidation products that form on samples and allows for a better understanding of the exact degradation mechanisms each material system experiences at temperature.


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## orvi (Dec 14, 2021)

no other option here. XRF won´t be that accurate (most of used machines, if any), gravimetric analysis without professional setup is out of the game... yes, only ICP-OES.


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## justinhcase (Dec 14, 2021)

I just use some analytical grade nitric acid, and look to see that I have a clear solution.
Even the slightest impurity will affect the colour.
I do have a spectrum analyser, but have never really needed to use it.


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## rockchopper (Dec 14, 2021)

Check out the "Sigma Metalytics Precious Metal Verifier" Does Silver and gold.


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## orvi (Dec 15, 2021)

justinhcase said:


> I just use some analytical grade nitric acid, and look to see that I have a clear solution.
> Even the slightest impurity will affect the colour.
> I do have a spectrum analyser, but have never really needed to use it.


When we are at the level of purity 99.95+%, when alloy contain say 0,01-0,02% of contaminant, aside of copper, i don´t think you could reliably tell only by looking at the solution. For 99,9 % could be clearly possible (to see mainly copper-ammonia). I encountered tin once as the contaminant in the silver bar, if I remember correctly it was somewhere around 0,05%. We refined this anyway in the cell. Small piece of this (not completely) pure silver was dissolved in nitric.
And i can say that solution was crystal clear, without milkiness.


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## justinhcase (Dec 15, 2021)

Unlike other nitrates, Sn reacts with water to produce an oxide which should be very visible with a large enough sample.
Sn + 2 H2O -> SnO2 + 2 H2


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## Lou (Dec 15, 2021)

1000 mg/kg vs 100 mg/kg is not a job for visual estimation.

Use ICP.


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## justinhcase (Dec 15, 2021)

Lou said:


> 1000 mg/kg vs 100 mg/kg is not a job for visual estimation.
> 
> Use ICP.


Emission spectroscopy (ICP-AES) and mass spectrometry (ICP-MS) are both highly effective chemical analysis techniques,
But that costs between £80 and £120 a run at a good lab.
What are you doing with the silver?
I sell silver nitrate back to my chemical provider, who runs quite extensive quality control.
He informed me that my product is all laboratory grade used in chloride test kits.
I must admit that I had to wait until I had a window in my processing that would allow me to eliminate all chloride based reactions in the work, aria and twice distil all my H2O before I managed a crystallisation I felt would hold up to testing.
That is an exceptional case, mostly if a buyer is testing my silver they are using a fire assay which will not really register trace contamination at that level.
How much money are you making buying the silver?
These are all relevant factors to consider when choosing a test method.


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## sar (Jan 20, 2022)

ISO 15096-2020
This document specifies a method intended to be used as the recommended method for the determination of silver of fineness of and above 999 ?. For the determination of fineness of and above 999,9 ?, modifications described in Annex B apply.
Also for assurance take an ultrasonic test for homogeneity of inside the bar.


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## Elemental (Jan 20, 2022)

I was going to publish ISO 15096-2020, but I see that it is has a copywrite. ISO 15096:2020
Cost: 58CHF (Swiss Francs) or $63.31 (US Dollars)

I am not advocating anyone purchase this standard, just providing more information about it. 

Elemental


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## orvi (Jan 20, 2022)

I trust you produce a high quality product. But in that trace quantities, visual isn´t the most reliable technique. Maybe some spectroscopic tester for Cu+indicator... Or nephelometry for trace tin content.
I´ve done a lot of "eye" analyses in my work. My opinion is that trace impurities could be detected reliably with trained eye to 0,05% level. Very specific test, if applyied (like Ni-DMG for example) could lower this number.

With unknown bar, refined with unknown process, it would be difficult to asses purity with just basic methods, without sensitive instrumental analyses.


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## sar (Jan 20, 2022)

Here is 2014 edition
Unfortunately I don't have 2020 edition

Sar, I have removed the document you attached because it is protected by copyright. We do not allow copyrighted material to be posted here. FrugalRefiner


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## campbellj46 (Apr 13, 2022)

A mass spectrometer analysis is the only way I would buy such a large bar. The lab cost is negligible if you're dropping that much coin for a large bar of silver.


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## Lou (Apr 13, 2022)

I'm bolder I guess. If I can melt it and it dissolves clear in nitric and doesn't "weep" during the melt and moreover, dissolves in ammonia, it's pretty damn pure silver. 

Lot of people don't want their silver melted or drilled. In small format, the density/weight you can determine well enough, but larger bars, there's little to no premium so it gets grained up and sampled as grain and run on ICP-OES.

Btw, Nickvc, a lot of bar producers are jerks that won't even look up their serial numbers.


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