kendur,
What bothers me about your question, is you have already got half way into this, and now asking how to finish, it reminds me of a man who has jumped out of the airplane, and then asks how do I work the parachute.
I assume you removed base metals before dissolving your values in aqua regia, (if not then much of what I say here may not work, also I am assuming all of the metals were dissolved in solution),
You should read Hoke's book, and get better details and instructions than I can give you in this post.
The aqua regia after dissolving gold can still have unused nitric acid in solution, this nitric acid will keep the gold from precipitating, and needs to be removed from solution, this free nitric acid will also keep the stannous chloride test from reacting (the test we use to tell if values are in solution), most people new to refining use way too much acid (and too much nitric acid), a simple way to lower the free nitric acid in solution is to use it up (adding gold to the solution and heat to use up the nitric acid), we can evaporate off the nitric, by concentrating the solution, this is done with just enough heat to produce fumes evolving from the solution, we do not want to boil the solution and loose gold in the process, a few drops of sulfuric acid can help here as it will keep us from cooking salts if we go too far in the evaporation process (it can also help to precipitate lead from solution), evaporate to a thick solution, add just a little HCl acid (not too much we just want to keep from forming salts), and evaporate again to a syrup, add just a little HCl again to wet, and one more evaporation, dilute this last evaporation with water. I use about four time the amount in water, let this sit overnight (silver chloride white salts will settle), decant and filter solution (a test with stannous chloride will tell you if gold is in solution and it is a good indicator that you have removed the free nitric acid so that your precipitation procedure should work), now you can add your choice of chemical precipitant like sodium metabisulfite or ferrous sulfate, or what chemical you like to use, to precipitate the gold, stannous chloride test again tells you where you are at, if you still have gold in solution or you have precipitated it out of solution.
Note: when evaporating off the nitric acid the solution gets to a point where the acid is concentrated, small bubbles will start to form, at this point the nitric will try to come out of solution in a vigorous reaction, if your not careful the solution will boil over and you could loose your gold in the process, so keep a close eye on the solution (do not have the heat too high) and be ready to turn down, or remove the heat when the solution gets to this point).
Also do not breath these fumes they are toxic.
If this solution is loaded with base metals, then you may have to resort to cementing the values out of solution using a copper buss bar.
Also if base metals were in the metals you were trying to dissolve, and you did not dissolve them all (your gold is most likely with those undissolved metals).
Again Read Hoke's book, She has all the answer's you need to do this right.
