Silver analysis help

[hrushi]

Here in India most of people use very old methods for testing purity

For eg. for gold test they just add double quantity of Ag and refine it and give the report. But in this case if Ir is present then report is not correct. But this can be detected in XRF.
And for silver Volhards method of titration is used for silver analysis. And here some notorious people who add low grade titanium and tantalum and some other elements which are not detected by Volhards Method.

I had also talked with Metrohm people but they were not able to answer my questions.

Which is the perfect method for getting the perfect purity of silver. Or What should be done to find these elements. I have tried XRF but as it was calibrated of Au reports i got were not perfect.
Thanks
Hrushi

 

[Harold_V]

My opinion?

A silver parting cell. They are easy to operate, and will return to you any traces of included precious metals, which isn't all that uncommon if you refine gold and the platinum group.

For best results, a silver cell should be fed high purity silver anodes (made from silver recovered by cementing with copper, or from converting silver chloride), although some claim to have successfully parted even sterling.

Harold

 

[hrushi]

I point is not refining but is how to do analysis before refining.
I am already into refining but due these faulty reports I am getting heavy losses so to avoid them I wanted to know either best process to verify these elements or to know which other elements are used as to add impurites in silver which are not known or detected in Volhards method and then try to find some method to know them before I take silver for refining.
Thank you
hrushi

 

[goldsilverpro]

I don't see why the Volhard titration method wouldn't work in this case. It is good that it doesn't detect Ti or Ta. It only will analyze the silver content, which you would want it to do. About the only interferences are with mercury or palladium. Mercury reacts the same as silver with the thiocyanate and palladium produces a color similar to the end point. As long as you can dissolve all of the silver present in nitric acid, I would think the method should work fine.

What losses do you mean? Silver or platinum group metals?

Did I misunderstand your question or your problem?

 

[Harold_V]

I point is not refining but is how to do analysis before refining.

Yep! I misunderstood your question.

Sorry Hrushi. That is beyond my knowledge. GSP has far more experience in that regard.

Harold

 

[4metals]

Gravimetric silver assaying was developed at the Calcutta Mint over 150 years ago, but with a little vacuum source and good filtration plus a drying oven it is a simple method that can serve you well today. Plus if your plagued by lead in the bullion, it is easy to detect it and remove it with this method.

Basically it involves dissolving the weighed metal sample in 50% nitric acid and dropping out a chloride and weighing it. Tared mini buchner funnels with glass filter papers make collection quick with a good vacuum and the sample, buchner and all is dried 110 C and cooled in a desicator and re-weighed. Any lead can be eliminated by rinsing the collected chlorides in hot water before drying, lead chloride can be rinsed free of the silver chlorides. Methods of using KI to detect lead have been posted on the forum before.