How do you determine the purity of a silver bar?

[ssharktu17]

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

 

[Lino1406]

XRF should do

 

[ssharktu17]

XRF should do

Does it get through plating?

 

[Lino1406]

If you drill to get inside, yes

 

[ssharktu17]

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?

 

[orvi]

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.

 

[ssharktu17]

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?

 

[nickvc]

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 .

 

[orvi]

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.

 

[Lou]

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.

 

[Lou]

Also,

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

 

[Lino1406]

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

 

[Ray Levi]

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

https://www.ebay.com/itm/JSP-Jewelr...2349624.m46890.l49286&mkrid=711-127632-2357-0

 

[pajarazzi]

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)

 

[ssharktu17]

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

 

[Lou]

ICP-OES.

 

[Elemental]

Inductively coupled plasma - optical emission spectrometry at UVA

Inductively Coupled Plasma Optical Emission Spectroscopy​

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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.

 

[orvi]

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.

 

[justinhcase]

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.

 

[rockchopper]

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