if you have mercury in your gold a retort is one way of dealing with it.
say you have gold, silver, lead. tin,and mercury,and other base metals.
nitric will eliminate most of the base metals,
(this solution has silver, lead and mercury and other base metals (Pd will disolve also)the silver lead and mercuy can be seperated from each other leaving the base metals by adding Hcl to make into aqua regia and treat as noted below)
lead,silver,and mercury are insoluble as chlorides.
gold and tin soluble as chlorides as well as other base metals.
many of these metals would need an oxidizer to disolve in HCL to make them chlorides, example nitric acid in Aqua regia, (4.5 patrs HCl 1 part HNO3) this will dissolve gold (PGM's if heated) and most all other metals making them a chloride solution.
then you will need to eliminate the oxidizer to prcipitate the metals from the chloride solution, boiling will remove the nitric evaporating it boil down to thick syrup but not to crystals add some hcl to keep it wet and do this again three times since we have lead add a few drops of sulfric acid to help it precipitate in later steps. I add some warm water and filter out insolubles from this.
then to this liquid add water to it till at least three times the volume.
this by itself will cause a white precipitant let sit till settle(I let sit over night cooler the better) I usually add a little table salt to see if any more silver is in solution if so it will precipitate a little more.
now this white powder is your silver,lead, and mercury, insoluble as a chloride, these can be seperated from each other. lets call this our silver group precipitant, see below how to seperate these.
the liquid contains your gold,(PGM's) and other base metals like tin copper ect.
I sypher off the liquid (decant) from the white precipitant and filter the liquid then add a precipitant to precipitate the gold (example SO2 gas, ferrous sulfate. sodium metabisufite, ect) this precipitates gold as brown powder let sit 24 hours (which will need rinsing and washed and refined again for purity) decant solution it will contain the PGM's and any base metals, Platinum and rhodium can be precipitated (and if lucky after platinum oxidizes palladium) using ammonium chloride, sodium chlorate will precipitate palladium.
now to seperate the silver group metals from the white powder above containing silver, lead, and mercury.
these are insoluble as chorides in water.
well lead is slightly soluble in boilng water and this can de used to seperate the lead from silver and mercury. boil in water then while hot filter the liquid lead cloride, from insoluble silver and mercury(when the lead chloride solution cools it will re precipitate the lead chloride)..
now ammonia will disolve silver but not the mercury this can be used to seperate them, by adding ammonium hydroxide disolving silver and filtering from insoluble mercury (which will not disolve in ammonia).
now since this silver solution still contains a chloride by adding nitric to make the base NH3 back to a acidic solution with HNO3 the silver will precipitate as a chloride and in sunlight silver chloride turns kind of gray violet looking.
that will leave the insoluble mercury, to test can be disolved in a little dilute Aqua Regia and hag a piece of copper wire into it the mercury will plate to it, wiping copper wire will show a bright shining coating of mercury plating.
I hope I didnt make to many mistakes on this.