Stannous chloride problems

[Imran]

Hello everyone
i tried to test my solution that could contain any remaining gold chloride after i precipitated most/all of it with metabisulfite. I added few drops of stanoous chloride test solution and few drops of my AR solution. Then white salt precipitated but no black dust. What do you think is that white salt?
thanks

 

[Oz]

Imran,
First things first. Make sure your stannous chloride is ok. Make a gold standard to test it with by digesting a very small amount (like finger foils) of gold in HCl and adding household bleach drop wise until digested. After foils are digested heat the solution to remove any free Cl2 gas that could interfere with a stannous test.

I always keep a known gold solution handy for verifying my stannous is working properly. If you get a negative result on a solution with a stannous test, the first thing you need to know is if it is just bad stannous chloride giving you a negative result.

 

[element47.5]

I can't say I know from direct experience, but logically, what else could it be, other than having excess acid precipitating the (stannous) tin? Or some other base-metal pollutant?

 

[Imran]

Sorry but i forgot to mention that i have already tested stannous on known gold solution and precipitate of black gold powder appeared, i also heated solution to evaporate any remaining nitric and chlorine but to no avail This salt is probably metastanic acid that form via reaction of some remaining nitrate and stannous.
tnx for quick reply