Continuing from Part 1 of this tutorial you have been told to remove the flask off the hot plate and allow it to cool back to room temperature and settle for about one hour. Next step is to filter the resulting solution free of any solids. And test it for precious metals presence with Stannous Chloride Test solution or with Dimethylglyoxime (DMG ) test for Palladium.
C. Palladium and Silver cementation. When done filtering, the solution may vary in color from yellow green to deep burgundy and now contains dissolved precious metals, mainly Palladium but may hold as well Silver chloride, Gold and on rare occasions some Platinum. The solution will hold along side those precious metals some traces of undissolved base metals such as Nickel, Barium, Lead and Tin but not to the point of harming the recovery process.
Those metals are very reactive with acidic solutions so be careful and add few pieces at a time, let them react all the way to completion before adding more. You bill be far better served using Zinc rather the Aluminum since Al tends to linger and stick to the precipitate.
Soon you will notice a color change in the solution and black precipitate swirling in the beaker, the black precipitates composed of all metals located lower the Al/Zn on the reactivity series.