The purest gold achievable commercially is typically produced through the Wohlwill process, an electrolytic refining method. This process increases gold purity to approximately 99.99%.
The Wohlwill Process Explained
The Wohlwill process utilizes electrolysis to refine gold. Here's a breakdown of the process:
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Anode Preparation: A casting of impure gold acts as the anode (positive electrode).
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Electrolyte Solution: The anode is immersed in an electrolyte solution composed of hydrochloric acid (HCl) and gold chloride (AuCl3).
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Electrolysis: An electric current is passed through the cell.
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Gold Deposition: At the anode, the impure gold dissolves into the electrolyte. Only pure gold is then selectively deposited on the cathode (negative electrode). Impurities remain in the electrolyte solution.
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Purification: The gold deposited on the cathode is exceptionally pure, reaching about 99.99% purity.
Simplified Explanation: Think of it like filtering. The electric current "filters" out the pure gold from the impure gold, transferring it to the cathode while leaving the impurities behind in the solution.
Why 100% Pure Gold is Difficult to Achieve
While the Wohlwill process yields very high purity, achieving absolutely 100% pure gold is extremely difficult, if not practically impossible, due to:
- Trace Contamination: Minute amounts of other elements might still be present.
- Analytical Limitations: Detecting the last traces of impurities becomes increasingly challenging.
Summary
The Wohlwill process is the standard method for achieving the highest levels of gold purity commercially available. It involves using an electrolytic cell with an impure gold anode, a hydrochloric acid and gold chloride electrolyte, and carefully controlled electrical conditions to selectively deposit pure gold on the cathode. Although 99.99% purity is achievable, 100% purity is exceptionally difficult to guarantee in practice.
