23/04/2026
Nitric Acid - Gold Processing Guide
Nitric acid gold refining uses acid to dissolve base metals (like copper, silver) from gold alloys, leaving pure gold behind because gold doesn't dissolve in nitric acid alone. The general process involves dissolving impure gold in hot, dilute nitric acid (often 50/50 with water) in a well-ventilated area, letting the reaction remove contaminants, filtering the remaining gold powder (which looks like coffee grounds), rinsing thoroughly, and then melting with fluxes (borax, potassium nitrate) to form pure gold. For higher purity or dissolving gold itself, aqua regia (nitric + hydrochloric acid) is used, but nitric acid is key for separating gold from base metals.
Key Steps in Nitric Acid Refining
1.Preparation: Melt gold scrap into shot or granules to increase surface area for better acid contact.
2.Dissolving Base Metals: Place gold shot in a Pyrex or plastic container, add hot dilute nitric acid (e.g., 1 part nitric acid to 1-3 parts distilled water), and heat gently (boiling water bath).
3.Reaction: The acid reacts with base metals (copper turns blue), releasing brown nitrogen dioxide gas; ensure excellent ventilation (do this outside or under a fume hood).
4.Completion: Continue until bubbling stops, indicating all base metals are dissolved.
5.Filtering: Carefully pour the liquid off (to save for other processes), filter the remaining solid (pure gold powder), and rinse with distilled water.
6.Melting: Mix the gold powder with fluxes like borax and potassium nitrate (saltpeter) to help impurities float, then melt into a pure gold ingot.
Compiled by “ Ideal Hygienic Technology Mining division - IHT Mining and Industrial “ Call +263782164820, +263718405892 [email protected]
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