This Safe Pickling Powder is used after heating applications and is excellent for removing flux residues from Argentium Silver. (Can be used with other metals.)
 
Instructions:
Mix 1-2 tablespoons of pickle powder with 200ml of warm/hot water.
Place the Argentium Silver piece into the solution immediately after quenching.
Leave in the solution for 10 minutes.
After 10 minutes remove the piece from the solution and rinse thoroughly.

100% non-toxic food grade materials. 
Non-corrosive and biodegradable.