How to test with Stannous Chloride?

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warrendya

Active member
Joined
Jun 11, 2008
Messages
33
Location
California
I've read a lot of posts instructing to always test with stannous but haven't come across one yet that actually describes how to do it. I actually do have Hoke's book and she says to use a spot plate. Not having one handy, I tried putting a drop of solution onto a white corian plate, then putting a drop of stannous solution on top of that. I'm certain my Au-Cl solution has gold in it (I treated fingers with AP, then dissolved the foils in the Au-Cl). I'm also sure the stannous is fresh (made it last night with 1.5 g tin powder in 20 ml HCL, heated til it fizzed then cooled).

Instead of the 2 drops of liquid turning purple, what happened was a whole bunch of tiny black spots appeared within the drops. It almost looks like something was precipitated by the stannous. I stirred the 2 drops to see if that would result in a uniform color, but the little spots do not want to mix; they remain distinct within a clear solution.

I tried the same method with a drop of pregnant AP (I watched this AP dissolve my foils when I tried to use AP to clean them up) and got the same reaction.

So, is this a normal positive reaction for gold?

Thanks!
 
The color of the test for gold will vary with gold concentration.

Purple is the most common, with black (actually a dark purple) being extremely saturated.

I dip a cotton swab in water first then drip a drop of the solution to be tested on the swab followed by a drop of stannous.

In the general reactions list I posted a photo of some positive stannous swabs.

Steve
 
I had a similar problem when I started testing with stannous. I paid too much attention to people like Steve and always got black test results with only occasionally having a purple fringe. Not the worst problem to have :wink:
 
I tried to put stannous chloride on a cotton after filtering,in the solution or even on the plated stuff. It always worked great when there was a gold there,but color changed from grey/purple to almost black depending on the solution or stuff tested.
 
I simply use a filter paper.

Upon it drop a tiny drip of which you want to test - it then quickly soaketh in to thy filter paper. With another drip dropper, drop a single tiny drip of freshly brewed stannous chloride onto the top of thy previous drip dropped - it then soaketh into thy filter paper.
After some seconds, if positive for gold, you should see a purple ring expanding henceforth from the center. Again, the darker the ring, the more gold in solution. Gotta love those black looking blotches!

Do the following, it is very handy, especially if you want to be *really* sure everything is testig ok.
I have a very small amount of yellow gold solution in a sealed test tube for double checking the stannous is working.

Stannous seems to work best when warm, and the tiny bit of tin still fizzing in the bottom. I just recharge it with a very small pinch of tin and over a bunsen till it fizzes a bit. The bit of tin dosent even have to completely dissolve. Just give it a minute or two fizzing.

I use a glass fluted pipette for the tiny drop dripper. You dont even really need a standard big drop, just enough to wet the paper.

Have a scrap cardboard under the filter paper, (and complete workbench) so acid dont get onto things you no want acid to get onto!

It works a treat, it has plenty of room for multiple uses, and you get to keep a record of your testing. I think it might fade after some weeks/months, so take a photo! heh..

regards
SK
 
I think I read a post that indicated iron chlorides would interfere with testing for gold. Is this true? If so, does it matter the state of the iron (ferrous/ferric)?
And are there other reasons why the stannous chloride test will produce inaccurate results?
 
Here's how I do it.

I never liked making up the traditional stannous chloride solution.

I put a drop, or two, of the solution I'm testing on a piece of filter paper. I chose a paper that won't absorb the liquid too quickly and allow it to spread out. I use the tip of my Case pocket knife and put just a few crystals of non-yellow (white) stannous chloride on the spot. I then put one drop of water on the spot and observe the color. Purple or black (near) means gold. I prefer S&S 596 paper but many papers will work. The same thing can be done on a spot plate.

I can't ever remember this not working, no matter what else is in the solution.
 
Thanks,
Is there an easy way I could make my own stannous chloride crystals and if so, how would be the beast way to store them?
 
I get my stannous chloride crystals from a seller on ebay. About $12 shipped for a 1/4 lb, which if you keep stored properly will be about enough for a lifetime.

The seller is quartzpegmatite (who has many other chemicals also). He is not very the cheapest, but has about everything a home refiner would need.

H.
 
Hi.
I have tried to make a SnCl2 solution from SNCl2 crystals bought from ebay. Made a 4% solution, but it isn't clear, it is milky white. tested various solution of which Ive already precipitated gold all of them, shown nothing? It seems odd to me. any idea why?
 

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