Old Stannous?

[Tauran]

Ok here's the story.

i purchased some pre bottled stannous off ebay for a few dollars. at the time i was not confident enough to make it no did i know how to.

it arrived today and i went ahead and tested my AP/pins solution which has been sitting there for about 3 days.
i ended up with no colour change at all. i also tested another small batch of gold liquid i believe to be AuCl also negative.

have i been sold a lemon and am i better off making some myself or am i missing something.

any help would be great.

 

[Harold_V]

You can determine if your stannous solution is active, or not, by testing a standard solution. Stannous chloride does have a shelf life---although many, here, claim it lasts for a long time. My personal experience didn't support that view. I made mine from crystals, and added a few pieces of tin each time it was made. I'd make about two fluid ounces, and used it regularly. I refined on a full time basis, so it was used daily (seven days/week). By the time it was running out (generally about three weeks), it would be losing it's ability to work. In the process, it changed to a rather opaque yellow color, and would respond very poorly to a standard solution, yielding, at best, a brown display when it should have reported a deep purple/black display.

The chance is that what you have works fine, but that your solution is barren. That can be true even if the solution has the familiar yellow/orange color, for other metals can yield similar solutions. A test with a standard solution is the answer, or you can test your (hopefully) gold chloride solution by placing a drop in a spot plate cavity and introducing a crystal of ferrous sulfate. It it bears gold, you'll see the solution change color and witness the growth of fine particles of gold, or even a thin sheet of gold.

For the record, a standard solution need not contain much gold. A couple grains in a couple fluid ounces is plenty. It's sole purpose is to determine if your stannous test solution works, or not. Indications are a standard solution has a good shelf life. Mine was kept in a dropper bottle and would last no less than three years. It got used only infrequently.

Harold

 

[Tauran]

thanks for that. i'll keep it for a more definite assay once i have an properly impergnated solution.