Anyone familiar with retrieving ore from aqua Regina that has been dried to a powder? A friend has some slurry that has been dried to powder, and wants to process the ores, if any, out of it. Would appreciate any reliable advice.
Sodium meta-bisulphate is used after reverse electroplating to dissolve the remaining metals and leave pure 24 kt gold. If he wants to recover other metals I've not a clue and it might not be economical.
aqua Regina is some very, very nasty acid.
it can ruin your health or kill you if you don't know what your doing.
there is a very good refining forum here.