# Why does a chemical compound precipitate metals differently than metal

In a solution of aqua regia (or other acids), if there is a precious metal dissolved, along with other metal ( such as other precious metals or base metals), and you add a powdered metal, you precipitate all the metals lower than it on the reactivity list.

If however, you use a chemical compound (such as sodium metabisulfate to precipitate gold or ammonium chloride for platinum), it predominantly only precipitates one particular metal.

Why is the compound selective?

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