Bloomglassworks,
There are many things you will need to learn here, fist you should study Hokes book.
Aqua regia should be used to dissolve gold, not base metals or gold and base metals.
You need Listen to your sister, she is correct urea and nitric can make dangerous compounds especially with metals and processes we use, many will suggest urea to de-NOx a solution, I never do, not only because of possible danger, but you add another impurity, urea will not destroy nitric acid, as most people who recommend its use believe, it will destroy nitrous acid or NO2 in solution, actually urea is often added to fuming nitric acid, for this reason when they want pure nitric acid free from NO2, the urea does not destroy the pure nitric acid, but removes the NO2 gas from the pure HNO3.
Learn to make your Aqua regia when dissolving gold with limiting the amount of nitric acid using only the amount of nitric acid needed and no more, this way you do not have nitric acid (oxidizer) to eliminate, when you do have some free nitric acid to remove use the evaporation process, evaporation and an added gold button, or sulfamic acid, to remove free nitric from your solution.
Aqua regia is a difficult to master, and needs understanding and practice to be able to use it, reading about it seems like a simple thing to use, but in reality can have many difficulty's for a beginner, solutions can be boiled over easy from the reactions, or during evaporation process when nitric in solution is concentrated, people will say you can dissolve any metals with your gold and make it sound simple to get your gold back, the internet is full of miss-information or missing facts, and either mislead you in your thinking or do not tell you the whole story or are just plain bunk, there are other methods to dissolve gold, especially when gold is in flakes, powders or foils or finely divided state, like HCl/NaClO (bleach), or HCl/32% H2O2, there are other solutions but these are the one you will want to learn about.
Copperas (ferrous sulfate) (FeSO4) has probably been used more throughout history than sodium metabisulfite (SMB) to precipitate gold, and works just as well sometimes better depending on circumstance, ferrous sulfate can be made at home easily (I have many post on how),if you buy your ferrous sulfate as a garden supplement it could be oxidized (brown), if it is brown do not use it will not work, the crystal salts of ferrous sulfate should be a pretty green color salt, the brown is oxidized iron salts and no longer copperas good to use to precipitate gold, using any precipitant to recover your gold is best used with testing, using your stannous chloride to help you determine the end point or if the reagent is needed or would even work, most of the reagents as a general rule use about as much in weight of reagents as gold in solution, copperas and SMB are not the only reagent that will precipitate gold from solution, each reagent will normally reduce other metals besides gold from solution (although most are fairly selective), here is were you will read in Hoke why she may choose one over the other depending what other metals may be in solution or where she will use a different reagent on the second refining to purify the gold as the different reagent used on the second refining would nor precipitate the same base metal the reagent in the first refining did.
You need much more than a few hundreds of hours of study before you beginning to use any chemical, and much more than this before you use aqua regia.
Begin your study with Hokes book.
Forget about trying to recover or refine at this point, all you would do is make dangerous messes lose your gold and other precious metals and put yourself and others in danger.
Your Lab work at first should be the getting acquainted experiments, you will be shown in Hoke's book, these are some of the most important things to learn in the beginning, how metals react in solution, which ones cause troubles, and how to recognize the reactions.
Study how to deal with the toxic waste, another most important task, this will keep you from not only going to jail when the authority's come to check you, and on what you are doing with the chemicals you have been buying, but also will help you to be able to treat the toxic hazardous waste so that you are not poisoning yourself or other people with these deadly solutions.
Study the safety section and other material so you do not poison your self with the fumes from these reactions many of which may not be detectable to your nose, some of which would only take a few lungs full to kill you or others that will damage your lungs to the point they will no longer work several years down the road, study also all of the acids and chemicals you use, many of which by themselves may not be that dangerous but when reacted with a metal or an ore can kill, some of which a few drops in the eyes could blind you for life burning the eyeballs out of your head, some acids and organics can create such flammable substances they could self ignite in your lab, many solutions and metals make explosives, This is not meant to frighten you but to emphasis the true dangers involved, study and understanding is your best protection, what you do not learn CAN KILL YOU...
your gold or other precious metals will not go anywhere while you study (if you just jump in head first you might just as well say bye bye to them),and while you study you can collect and prepare your material for when you have studied and have a good understanding of the process from beginning to end, including how to deal with waste, this way you will collect enough values, and have a good understanding of how to recover and refine those values.
so i have to find the moss killer type then
