Hi kadriver,
Thanks for sharing your experiments, especially the pictures, staying in sharp contrast to a lot of photographic "artwork" shown up in this forum. Up to now, I have three comments regarding your posts:
1.) The title of the thread is simply wrong, because a salt like "ammonium hexachloropalladate(II)" doesn't exist. What you mean is ammonium hexachloropalladate(IV). The roman ciphers in the name stand for the oxidation-state of palladium in the respective compound, and this is IV (+4) in the only sparingly soluble (NH4)2PdCl6, ammonium-hexachloropalladate(IV), containing Pd(IV). There exists a chloro-complex-salt of Pd(II) too, ammonium-tetrachloropalladate(II), (NH4)2PdCl4, which is much more soluble in water, and as a solid, forms dark brown, needle-shaped crystals.
2.) In your last post from August 1st you ask for a flocculant: "Is there a flocculant that I can use to get this to settle quickly and not interfere with the reactions?" - To me it is not clear, what you mean by "this": the title-compound to be precipitated or the freshly washed, acid-free Pd-black? - Anyway, (NH4)2PdCl6 usually forms well formed, easily filtrable crystals, and a flocculant is not needed.
Pd-black, especially, if washed free of acid and/or dissolved salts tends to peptisize in water, that means, it seems to form sort of a colloid, settling only difficultly. According to my experience, in this case, it is sufficient, to add one tenth of the suspensions volume 32% HCl (muriatic acid), and give it, constantly stirring (e.g. with a magnetic stirring bar), a short boil during a few minutes. Usually the finely suspended Pd-black coagulates and becomes filtrable much better.
3.) For safety-reasons I, personnally, would not precipitate (NH4)2PdCl6, but the corresponding potassium-salt instead, K2PdCl6. Doing this, you never will have issues with NCl3 and/or potentially explosive chloramines.