Gold is typically "tried," or tested for purity, through a process involving melting and treatment with chloride. This method, and other techniques, are used to determine the quality and authenticity of gold.
Here's a breakdown of common gold testing methods:
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Melting and Chloride Treatment (Refining):
- The process begins with melting the crude gold.
- Chloride is introduced to the molten gold.
- This converts impurities (foreign elements and minerals) into chlorides.
- These chloride compounds volatilize, effectively separating them from the gold.
- This refining process can yield gold that is approximately 99.5% pure.
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Acid Test:
- This is a common and relatively simple test.
- It involves applying nitric acid to a small, inconspicuous area of the gold item.
- If the item is not gold, or if it has a low gold content, the acid will react and dissolve the base metals, leaving a visible mark.
- If the item is genuine gold, it will not react with the nitric acid. Different karat values require different acid solutions for more precise determination.
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Electronic Gold Tester:
- These devices measure the electrical conductivity of the metal.
- Gold has a specific conductivity, so deviations indicate the presence of other metals.
- These testers are relatively quick and non-destructive.
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X-Ray Fluorescence (XRF) Analysis:
- This is a highly accurate and non-destructive method.
- XRF analyzers use X-rays to excite the atoms in the sample.
- The emitted radiation is then analyzed to determine the elemental composition of the sample, including the percentage of gold and other metals present.
- This method provides a detailed analysis of the gold's purity and composition.
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Specific Gravity Test:
- Gold has a high density. This test leverages that principle.
- The item is weighed in air and then weighed when submerged in water.
- The difference in weight is used to calculate the specific gravity.
- Comparing the calculated specific gravity to the known specific gravity of gold can indicate purity.
In summary, trying or testing gold involves various methods, ranging from simple acid tests to sophisticated instrumental techniques like XRF analysis, all aimed at determining its purity and authenticity. The melting and chloride treatment method refines the gold, increasing its purity by removing impurities.
