Stannous test false NEGATIVE?

[OldManSam]

So I was refining a *particularly* dirty parcel yesterday, but one which had a known gold content. I had a hell of a time getting all the metal into solution, but when I finally did I was tired and decided to go to bed. Before I went to bed, however, I stannous tested the hot solution.

The stannous test was an unequivocal *negative.* Absolutely zero color change. Puzzled by this I shut everything down and crawled into bed.

This morning I tested it again, and again the result was absolutely no reaction.

I decanted the solution and there was no sediment or precipitation. Getting frustrated, I ran the entire solution through my buchner. It caught a little bit of junk, but not much at all.

Getting pissed off, now, I dumped a few spoonfuls of SMB in amd stirred it up. Plenty of foam, and the liquid turned absolutely black as night.



About an hour ago I refiltered it through a pleated filter and *this time* it caught a ton of gold.

I cut the tip off the filter and dropped it into a clean beaker with HCl and Nitric, redissolved it as normal, filtered it one more time, and stannous tested it. The test strip immediately turned inky black.

What could cause a negative stannous test like that? Would a colloidal solution cause this? If so, why would SMB work? Or did it actually work??? Did something environmental break the colloid?

I'm so confused?

 

[Golddigger76]

My guess is that since you had a hell of a time getting everything into solution that you overshot the nitric, I did not see that you denoxed it.

There's a few other things that can cause this to happen ,,, If your stannous chloride is old or weak,
Or if there's too much nitric and not enough gold it can re-dissolve your gold faster than you can see it precipitate with the stannous chloride.

Another thing is if it is a very dirty solution it can make it harder to read the stannous test with dark colored solutions.

Obviously how you do the stannous test also matters.
I'm not a fan of the spot plate test but some people swear by it.

I always test with a Q-tip, or a drop of stannous chloride next to a drop of solution on a piece of filter paper.

Hope this helps.

 

[Yggdrasil]

So I was refining a *particularly* dirty parcel yesterday, but one which had a known gold content. I had a hell of a time getting all the metal into solution, but when I finally did I was tired and decided to go to bed. Before I went to bed, however, I stannous tested the hot solution.

The stannous test was an unequivocal *negative.* Absolutely zero color change. Puzzled by this I shut everything down and crawled into bed.

This morning I tested it again, and again the result was absolutely no reaction.

I decanted the solution and there was no sediment or precipitation. Getting frustrated, I ran the entire solution through my buchner. It caught a little bit of junk, but not much at all.

Getting pissed off, now, I dumped a few spoonfuls of SMB in amd stirred it up. Plenty of foam, and the liquid turned absolutely black as night.



About an hour ago I refiltered it through a pleated filter and *this time* it caught a ton of gold.

I cut the tip off the filter and dropped it into a clean beaker with HCl and Nitric, redissolved it as normal, filtered it one more time, and stannous tested it. The test strip immediately turned inky black.

What could cause a negative stannous test like that? Would a colloidal solution cause this? If so, why would SMB work? Or did it actually work??? Did something environmental break the colloid?

I'm so confused?

My guess is that your Stannous has gone bad, have you tested it with a Gold Standard solution?

Edit for spelling

 

[anachronism]

Keep a small vial of known gold solution to hand and give your stannous a quick test every day you use it. It's then really simple to know you're on point as you work.

 

[Martijn]

So I was refining a *particularly* dirty parcel yesterday, but one which had a known gold content. I had a hell of a time getting all the metal into solution, but when I finally did I was tired and decided to go to bed. Before I went to bed, however, I stannous tested the hot solution.

The stannous test was an unequivocal *negative.* Absolutely zero color change. Puzzled by this I shut everything down and crawled into bed.

This morning I tested it again, and again the result was absolutely no reaction.

I decanted the solution and there was no sediment or precipitation. Getting frustrated, I ran the entire solution through my buchner. It caught a little bit of junk, but not much at all.

Getting pissed off, now, I dumped a few spoonfuls of SMB in amd stirred it up. Plenty of foam, and the liquid turned absolutely black as night.



About an hour ago I refiltered it through a pleated filter and *this time* it caught a ton of gold.

I cut the tip off the filter and dropped it into a clean beaker with HCl and Nitric, redissolved it as normal, filtered it one more time, and stannous tested it. The test strip immediately turned inky black.

What could cause a negative stannous test like that? Would a colloidal solution cause this? If so, why would SMB work? Or did it actually work??? Did something environmental break the colloid?

I'm so confused?

It was not colloidal gold (nanoparticles of elemental gold, which are not in solution), since SMB had a result.
Did you test the solution with stannous after dropping the gold with SMB?
As said excess HNO3 can hold back an Au positive result or make it disappear again after testing.
Since you had a black result after the second dissolving step, your stannous obviously works.

I guess we all know not to: but this shows one letter can make a big difference in chemistry.

your Stannous has gone bad, have you tasted it

 

[Martijn]

A great way to get gold in urine....