stannous chloride test

sayf

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Hello every one , after precipitating gold from.aqua regia using iron sulfate , i did a stannous test to make sure that no gold is left behind but i got (what i think) a positive test for gold now am wondering why the test is positive giving that i surly used more iron sulfate than the needed to precipitate all the gold , any ways my aqua regia before precipitation was deep green indicating that my aqua regia has lot of copper inside , so here is my question :
can the stannous test detect copper in aqua regia solution because a friend of mine said that stannous test for copper in aqua regia has lot of similarites with stannous test of gold in aqua regia

Any ways i attached two photos for the test ,both of them are taken after gold precipitation and filtration
(Notice the test color on the cotton is brown)
 

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FrugalRefiner

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The brown color looks like what is called a "false positive".

Yes, copper can cause it.

Dave
 

nickvc

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I have to agree with Dave, if you had a purple stain then I would suspect gold but as it is brown I’m forced to say you have no gold left in solution.
Test a few samples of solutions known to contain gold and then dilute them in degrees until you get just a very faint positive for gold, you will never mistake the results again.
 

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