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Sulfurous acid as reducing agent for gold
Sulfurous acid is known to destroy the excess nitric acid and eventually precipitate gold from the gold-aqua regia solution. I tried adding an excess of 5-6% of its AR grade. After a while brown clouds appear and get denser. However, it also easily disappeared as the solution warms up. The solution's color turned from reddish orange to a much lighter yellow orange. What could possibly be wrong that the gold did not precipitate? Is it because I just got a trace of gold? Should I use another reducing agent as sodium meta bisulphite?
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