Should be no reason to evaporate at this stage, you should save the powders until you have studied more to understand each step before trying it.
After collecting the cemented powders.
You can incinerate the powders in a corning casserole dish on a hot plate, using a torch to get powders red hot, you can also do almost all of the whole process in this dish leaving powders in it almost the entire process, the rinses and acid treatments or liquid can be decanted from this dish, leaving the powders in the dish and adding and removing liquids, I use a lab tool that resembles a turkey baste suction tool with bulb to remove liquids, pipettes are nice to get the last drops.
Depending on the materials used with the Shor step would make me decide which acid I would choose to remove base metals first.
If much solder was involved the tin content may still be high, this could be a problem if going to nitric acid, or for filtering solutions later, we want to remove tin before putting gold into solution, in this case a boil in HCl will put tin oxide and some of the base metals above hydrogen in the reactivity series of metals into solution, decant the HCL after powders settle well, the color of the decanted solution can be an indicator if another treatment will dissolve more base metals and should be used, the powders can then be washed with boiling hot water washes lowering heat and letting powders settle well before decanting liquids (decanting very warm will help to remove lead chlorides.
Remember test all solutions for values.
That leaves copper and other base metals, for this I would choose nitric acid.
But I cannot add it to these powders which will contain chloride salts or liquids, nitric acid would form a form of aqua regia with these salts, and it can put my gold into solution before I am ready.
So I would give these powders a wash in sodium hydroxide solution heating a little stirring well and then let powders settle, decant and use water to wash chloride salts formed, after several water washes, put powders on low heat to dry slowly at first we do not want the water gases trying to escape splash out our powders, raise heat as it dries keep powders crushed and stirred, incinerate them again.
Cool the powders and give a wash in water, now you can use nitric acid to remove base metals, and rinse this with water.
Aqua regia is hard to learn so I suggest you do not use it at this point.
In this case I suggest drying and heating the powders to a couple of hundred degrees to remove nitrates, we do not need to heat the powders to red-hot this time.
Now the powders can be dissolved, cover with HCl, heat to low, add bleach with your pipette in small doses to dissolve the gold, the solution should look yellow of gold chloride, after the gold is dissolved, heat for a while to let any excess chlorine be driven off with the heat, turn off heat, let the solution settle again, decant solution through a filter into your clean jar you use to precipitate gold, the insoluble material left I would put into the stock pot, or with the filters to be burned later.
Now you should be ready to precipitate the gold........
Others may treat this differently.
