Stannous chloride in the solution added tin.
Tin in a solution of dissolved gold give problems when trying to recover or test for the gold, it can make filtering a problem. Basically making a mess of the solution.
The stannous chloride test is done with drops of liquid (drops from our gold solution we wish to test) either in a white spoon or a spot plate, or on a Q-tip or filter paper, then drops of stannous chloride are added to this, to see if there is a reaction or change in color to violet, or another color if possible Pt or Pd.
When you dissolved your necklace in aqua (I do not know the Karat or if it was gold, or if you removed base metals with nitric first...), (so some of what I say here is assumption on my part), you probably also have base metals in solution, and the stannous (or tin) you put into solution could have precipitated some base metal from solution, gold if in solution could be reduced but it would not precipitate, it can just form colloids which are now hard to detect in solution, still so small you cannot see them, they would be so small they will pass through a filter (that is if you can filter the tin gelatinous compound which can also trap some gold), basically now you have a mess that can be hard to deal with.
It does not look like you have much solution, what I would do is evaporate it down slowly to a very thick solution, once it was thick I would sprinkle in some NaOH powder (to lower acidity and to convert acids to salt water sodium chlorides, where you can remove as much chlorides from the values as possible, gold in an incinerating roast with chloride can make some of the gold volatile and go up with smoke), stir, just add enough NaOH to make a clear solution of salt water at around PH7, and let metal powders settle, use a pipette to decant the clear salt water, rinse the sludge several times with plenty of water heat to a boil and then let it settle again, and decant salt water (test the rinses for gold), once the powders are rinsed of chlorides as much as possible.
Slowly on low heat evaporate the liquid from powders (very low heat until the powders dry), once dry crush the powders and raise the heat, the may fuse and become soluble again, if they do lower heat so the syrup does not form popping bubbles splashing values from your dish, and continue on low heat till dry again, crush them to powder, and now raise the heat to high, you may see smoke of acids or salts leave the powders, bring the powders up to a glowing red hot and keep them glowing red hot while stirring them, if your hot plate or whatever you heat on cannot get this hot a propane or other torch can be used, stir the powders while still red hot, we need to expose these red hot powders to oxygen so that we oxidize the base metals, many time the powders will darken from oxidation.
I prefer to do this in a Corning-ware pyroceram dish.
Now let the powders cool, Here I normally use water from a spray bottle and rinse down the sides of the Dish, cover the powders in water and heat to a boil lower heat so powders will settle then decant the rinse water with my suction tool and pipette.
Then I cover powders with HCl and bring to a boil, lower heat so powders settle well, I try to keep solution warm so I can decant any dissolved lead chlorides, but want all of my gold powders to settle well, (but the powders not being stirred by the heat), decant the HCl wash, if this wash shows a lot of color, I will do another HCl boiling hot wash, if not much color I will do several boiling hot water washes again to remove any dissolved base metal chlorides, decanting the water washes hot also helps if there are lead chlorides involved.
Now I can start over with what I wish to do with these gold powders.
If I wish to do a nitric treatment to remove base metals here, I would repeat the process above, and remove chlorides as much as possible and incinerate again (but without the HCl boil), this is to remove traces of chloride that would dissolve gold when I used nitric acid.
Or
If I was satisfied I had base metals removed, (and decided I did not need a nitric treatment to remove base metals but not dissolve the gold), then I would not have to repeat the incineration process that removed the chlorides (the second time), and could just move on to aqua regia where I dissolve gold.
Study Hokes book keep reading it until what you read makes sense to you, sometimes we have to read something a couple of times before the concepts she teaches becomes clear to us, there is so much information in the book it is hard to grasp everything by just reading it once, much of what you learn from the book is an overall picture of how to recover and refine, understanding concepts that may not be clear when you first read each page, but later become clear to you, as you contemplate the overall book, of how she chooses different methods for different types of material, or may deal with different materials differently because of the other metals involved, or does a process differently to remove troublesome base metals...
After you read it a couple of times much of this whole picture is normally seen much clearer.
Practicing the getting acquainted experiments in Hokes book, and the experiments of testing metals in solution are very valuable tools, these give you hands on knowledge of how the metals react, she also encourages reader to come up with more experiments of their own, like the ones she describes in her book, doing that and doing experiments of your own, you can learn a lot about recovery and refining, and reactions you may see as you do, learning what may work and what may give you troubles.
Hoke's also has a book for testing jewelry for precious metals, with these tests you would not of had to dissolve your necklace to test it. that book can also be found on the forum as a free download file.
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