Charles,
you will want to be sure to inquarter the gold and pour shot.
if you measure out the HNO3 and add it in small amounts letting each reaction play out and dissolve as much gold as it can, before all of the gold is dissolved raise the heat some, it makes the acids more aggressive, and can be somewhat concentrating the solution as you are working to dissolve the gold, the heat will also make small amounts of free nitric more active and can help to use it up as it dissolves the gold, before all of the gold is finished dissolving, I will normally begin my first evaporation, this uses up nitric already involved and as the solution gets concentrated I can add a few drops of nitric at a time to finish dissolving the gold, this way I end up with very little to no free HNO3 to remove.
I evaporate till the solution is very concentrated, first mostly water evolves then free nitric then any free HCl as we concentrate the solution, as long as you do not boil the solution the gold chloride will remain in solution and will not leave as vapors, so basically this gold salt solution concentrates as we drive off free excess water and acids, the gold chloride will get darker yellow in color (if copper is not involved to make it green or brown), as you concentrate this yellow color gets darker, when really concentrated the solution takes on an orange to reddish color, this is normally my goal during concentrating the solution, but the main thing is you do not cook the liquid gold chloride out to salts or burn these salts to the bottom of your pan, a few drops of H2SO4 as recommended by C.M. Hokes, when she describes the process in her book, can help to keep the gold from forming salts so easily, as sulfuric acid or sulfates are not very volatile at all, and will remain when all most every other acid or liquid has been vaporized off.
I normally will add a sprinkle or two of sulfamic acid, after the above processes, mainly just to be sure.
actually you may not have any free nitric with the first process of adding HNO3 only as needed,but if there was the three evaporation process would take care of that, the sulfamic will get any nitric if there was even a possibility it made it this far, this process I use is overkill, but I really got tire of having free nitric left in solution giving me trouble (so I guess I over kill the nitric acid).
The stannous chloride test is also a good indicator of whether you have free nitric acid in solution, because for the stannous chloride to develop the purple of Cassius the gold has to be reduced to colloidal gold metal particles, this will not happen if free nitric keeps re-oxidizing the gold at the same time the stannous is trying to reduce it, basically with free nitric in solution the nitric keeps taking the electron from the gold the stannous chloride is trying to provide.
