Chemical Familiarization, Karat Gold and Stannous Chloride

[Phishin_ca]

The Stannous Chloride is dead.
Following Dave's suggestion of using a standard solution only when you receive a false positive,

I'm not sure I ever suggested that. I have said that I don't test my stannous as long as it's giving a positive result. I don't need to because it's obviously still working. If it gives a negative result, then I'll test the stannous to make sure the negative is valid, and not the result of oxidized stannous.

Dave

You are correct. I misspoke. I meant to say false negative. I knew there should be a positive result but did not get one. Sorry about that.

 

[Phishin_ca]

Another update. The Stannous Chloride is dead.
Following Dave's suggestion of using a standard solution only when you receive a false positive, I went a step further. It is pretty quick to make up a tiny bit directly on my spot plate. I noticed an extremely slow reaction to the test with my trusty bottle and I wondered if it was caused by excess oxidizer. A shaving of lead free solder on the plate followed by a couple drops of HCl and waiting (argh), gave me a fresh batch that turned black immediately.

I am almost tempted to no longer keep any for testing and just make new in spot 12 everytime before I start work.

If you read and pay attention on how to store it you would not have this problem.

The tin in the bottom of the vial was depleted.