Stannous Chloride Test Intrepretation

[RickRag]

Hi Guys,

I have tested my gold and PGM solution with SnCl to determine if all of the gold has been dropped. I notice that over the course of a few minutes up to a half hour the colors seem to change rather dramatically on the filter paper. I am including pictures of what I have observed. At what point should one make any conclusions about the test results. Immediately, after a few minutes or after the sample has had time to dry? The slight brown in the center of the 1 minute picture is a much darker brown the instant SnCl is dropped onto the filter paper but as you can see it quickly fades to pink and then seems to blend with the fainter yellow of the larger spot over time The timing appears to be critical in making the correct decision about what is and isn't in solution. Can someone help with this as I want to be thorough and recover all the gold without adding too much SMB.

 

[Lino1406]

This test is positive - dark in the middle

 

[RickRag]

Hi Lino,

I know its positive but for which metals? Most (if not all) of the gold has been precipitated but I know both platinum and palladium remain in solution. Are you saying this is positive for gold?

 

[Lino1406]

Can be each of them but remember the test is very sensitive to ignorable amounts

 

[EMRE]

What is the beginning material? What did you digest? Also paper touching the surface may be a problem of contamination. İ suggest suspend the paper in the air and wait few minutes. Usually results should be known right away though. İ am suspecting some iron ans may be pt as much as i can see from tue pictures.

 

[RickRag]

The solution tested was originally white dental scrap, directly dissolved in aqua regia, no inquartation. I precipitated the gold (at least most of it, which is the basis for my question) and am wondering what values might remain. I expect there to be Pd and maybe some Pt. Unlikely to have any other values but likely some base metals. Which ones? Does the gold appear to have been completely dropped? There is no purple/black indicator.

Really, the question is fundamentally about when to make any determination about results. Immediately? After a few minutes? Does this test fade as quickly when other values are present? Does concentration affect fading? Or only content?

 

[g_axelsson]

Have you read "Testing precious metals" by Hoke?
http://goldrefiningforum.com/viewtopic.php?f=54&t=25181
Göran

 

[4metals]

The stannous chloride test is most sensitive and fastest in detecting gold in solution. So much that if there is recoverable gold remaining in solution, the dark positive stannous stain will mask the more subtle coloration of the remaining platinum group metals. So if you are seeing the reddish and green stains which develop after a few minutes, your gold is long gone.

 

[RickRag]

Thanks 4metals, just the answer I was looking for.

 

[Yggdrasil]

There has been discussions lately on Stannous tests.
From time to time there pops up stannous test with atypical colors.
Do anyone have a list of what elements Stannous reacts to and what colors this create, beside the usual suspects that is.
I have heard about Molybdenum and Cobalt, not confirmed though.
Sometimes you have a thick yellow color which mixes slowly (high viscosity?) and sometimes red/pinkish color.
For the sake of being able to help people, it would be nice with an extended list of reactions and colors.

 

[Cheffrey17]

There has been discussions lately on Stannous tests.
From time to time there pops up stannous test with atypical colors.
Do anyone have a list of what elements Stannous reacts to and what colors this create, beside the usual suspects that is.
I have heard about Molybdenum and Cobalt, not confirmed though.
Sometimes you have a thick yellow color which mixes slowly (high viscosity?) and sometimes red/pinkish color.
For the sake of being able to help people, it would be nice with an extended list of reactions and colors.

I just posted a question about this very thing, you said you heard about the colors for molybdenum and cobalt in a stannous chloride test? Do you remember what those two show up as?

 

[Yggdrasil]

I just posted a question about this very thing, you said you heard about the colors for molybdenum and cobalt in a stannous chloride test? Do you remember what those two show up as?

Since nobody actually chimed in I do not know.
But there was a discussion hinting to red/maroon color without any more confirmation.