Ammonium hydroxide

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Ammonium hydroxide ( NH4OH, also called ammonia) is the water solution of ammonia. It is sold as household ammonia.

WARNING!

Never let a metal salt solution with ammonium hydroxide dry up, always acidify when done. If a metal solution with ammonium hydroxide is allowed to dry up, explosive compounds can be produced.

Ammonia in refining

In refining ammonium hydroxide (or commonly just called ammonia) is used to wash silver chloride from precipitated gold powder in the final wash. It dissolves both silver chloride and copper chloride. After the wash the waste liquid should be acidified with hydrochloric acid to avoid creating explosive compounds.

The waste after acidifying should be kept from other acidic wastes. The ammonium chloride could chelate any nickel or copper salts in solution and make waste processing a lot harder.

References

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