Ok, I tried to make the Stannous Chloride, but I couldn't find a source for tin localy. So, I decided to try using a 95/5 Tin/Antimony Solder. Unfortunately, I grabbed one with Acid Core Flux. I reaserched the flux and I believe it is Zinc Chloride. Not good, since zinc is much more reactive than tin. After disolving the solder, I was left with a dark residue on the bottom. I thought that might be the tin displaced by the zinc, but when I pored off the solution and put fresh HCL onto the residue, it didn't react at all. What could this residue be?