For l purposes only!
Leave refining to the refiners.
Assuming that you started with Aqua Regia gold solution, precipitated
gold with zinc, precipitated silver with solution of Sodium Chloride.
Now you have solution containing Platinum Group metals. Ammonium
Chloride will precipitate platinum our of solution. Palladium a bit
tricky. When you add Ammonium Chloride nothing will happen.
After that you nave to slow add Sodium Chloride crystal by crystal
and stir gently until precipitate forms.
Warning! This is not step-by-step instructions. Practice is far more
complicated than theory. Handling dangerous chemicals require
training and experience.