I have not tested it yet, but I am sure that gold in there...
You may be sure gold was in this solution at one time, but you do not know if it is still in the solution now or not.
If you did not test your solution you do not know where your gold is.
You need to determine if gold is still dissolved in solution, or if the iron in the nails has cemented it out of solution.
You can make your stannous chloride solution with a little HCl and tin, to test for gold in solution.
Without this test you do not know if the gold is still dissolved or if it is with the powders and iron nails.
You possible could have gold in the powders with the nails, and maybe some in solution.
With a little gold and a lot of nails, I suspect most of your gold will be in the powders with the nails.
Let the solution settle separate the liquid from the powders (and nails).
Treat these separately.
Test the liquid with stannous chloride for gold in solution.
If the test of this solution is positive for gold, you can use sodium metabisulfite to precipitate the gold.
If the solution tests negative for gold, your gold must be in the powders and with the nails. In this case treat the solution for waste, and work on the nails and powders.
Instead of sodium metabisulfite, you can make your own ferrous sulfate, and use it to precipitate the gold.
Ferrous sulfate can be made with dilute 10% sulfuric acid and clean soft iron.
If you wish to learn to make your own ferrous sulfate I can help you with that.
An alternative to using the chemical precipitants (like sodium metabisulfite, or the ferrous sulfate) or as a method of recovery (if the above chemical precipitants will not work) you can use a thick clean piece of copper metal to cement the gold out of solution, by putting the clean copper bar into the acid that contains gold, a little of the copper bar will dissolve, and the gold in solution will cement out as black powders, some of this black powders of gold may stick to the copper, you just brush off the gold from the remaining copper into solution, cleaning the remaining copper bar, rinse and dry the copper metal bar put it in a plastic bag for use later (the next time you have trouble getting gold out of solution)...
Sodium metabisulfite or ferrous sulfate these are chemical methods used to refine gold.
Cementing the gold out of solution with copper metal is a recovery method, used to recover the gold from solution, or where a chemical precipitant may give you trouble getting the gold out of solution, or where the chemical precipitants may not work well (like in a highly contaminated solution of base metals), the gold will not be as pure when cementing with copper.
The chemical precipitants work best with fairly clean solutions; they will leave most of the other metals in solution, and precipitate the gold.
Copper is used more for contaminated solutions or where a chemical precipitant will not work as well, the black gold powder when cementing on copper can have some copper in the powders (which can be dealt with), Using the copper bar to cement the gold also leaves most of the other base metals in solution, but it will have more copper involved.
As for dealing with the nails and powder (separated from solution):
It also would not hurt to screen (use a poly type plastic screen) the undissolved metals from the powders, and using some HCl and a brush to clean off the nails in the screen using an old toothbrush.
The nails could go to your stockpot for recovery later if any gold was left plated onto them.
(You could also use these remaining nails to make yourself a batch of ferrous sulfate, nails normally would not be my choice of iron but in this case they could be used)...
The powders could be heated in HCl to dissolve most of the iron, (or treated with HCl and 3% hydrogen peroxide to dissolve iron and copper), leaving you with mostly gold (and possibly some iron oxide or hydroxides).
Use only one of these methods, to get the gold out of solution. Do not combine them.
(The copper metal can be used to cement the gold if all else fails).
Cementing gold with copper works better for a dirty solution, where the chemical precipitants like sodium metabisulfite or ferrous sulfate may not work, or where you may have trouble recovering the gold.
The copper can be used after trying a chemical precipitant, if they do not work.
But it is not used with them, use only one method, these are different methods to get your gold dissolved gold out of solution.
Do you mean, put the copper on aqua regia and after dissolve on AR and then put SMB, for helping the gold appears in AR?
No.
After testing the solution for gold if you get a positive test, you can use a chemical precipitant like sodium metabisulfite, or ferrous sulfate, to precipitate the gold. If the solution is not too contaminated, (but do not use both, just one or the other), if these fail, and you still test positive for gold in solution you can use the copper buss bar to cement gold from solution.
You can first try SMB (sodium metabisulfite), or ferrous sulfate, (not both), or use the copper, (but not together) these are different methods.
The copper can also be used after one of the chemical precipitants like SMB, if they will not work (normally because of a contaminated solution), (but the copper is not used with them at the same time).
To use copper just put the clean thick solid copper bar into the acid solution that contains dissolved gold, you can stir the solution with the copper bar every once in a while, the gold will turn black and cement out of solution as a black powder, some of this black gold powder may stick to the copper bar (which can be cleaned off with an old tooth brush later), leave the copper bar in solution (stirring now and then) until no more gold (black powders form), then clean off the copper bar by brushing the black powdered gold off of it into the solution, let this sit and the black powders settle to the bottom, after the black gold powder settles, decant (by siphoning or pouring off the acid solution) without disturbing the black gold powders, (test the solution again for gold and treat the solution for waste if it tests negative for gold), the recovered black gold powders can be washed and then refined again.
about you told me: "especially if heat is involved in the process, the red rouge of iron hydroxide (rust) which is very resistant to acids even aqua regia"
Iron in a chloride solution if heated strongly can form iron oxides (a red rouge powder) that resemble red rust, you can also have these red powders from the nails, which could actually be rust of iron nail. The red rouge powder of iron is pretty much acid resistant (almost impossible to dissolve) even in aqua regia, where you can dissolve gold from this red rouge powder without putting much iron in solution from these red powders.
Basically I think you may run into this red powder while you are recovering your gold, they are normally not much of a problem, I was just telling you about them, and that you may see them while working on this...
Do you mean there's will be red powder after i put SMB?
No
I am sorry if I answer too much...
I probably make this harder for you to understand, by adding so much at once, but I feel that once you do understand it will be more helpful to you.
