Why Refiners Test for Gold in Solution
During gold refining, the metal is dissolved into chemical solution before it can be recovered. At this stage the gold is no longer visible and exists as dissolved gold chloride.
Refiners use stannous chloride testing solution to confirm that gold is present before attempting precipitation.
This test helps refiners:
• confirm gold dissolved successfully
• verify gold remains in solution
• avoid wasting precipitation chemicals
• check whether gold recovery is complete
The test is extremely sensitive and can detect very small amounts of dissolved gold.
What Is Stannous Chloride?
Stannous chloride is a chemical reagent used by refiners to detect precious metals in solution.
When a drop of stannous chloride contacts a solution containing dissolved gold, a chemical reaction occurs that produces a purple or dark brown color.
This reaction indicates that gold is present.
Because the reaction is very sensitive, it can detect even trace amounts of gold remaining in solution.
Materials Needed
To perform the test you will need:
• Stannous chloride test solution
• Filter paper or testing surface
• Glass stirring rod or dropper
• Small sample of the refining solution
Many refiners keep a bottle of premixed stannous chloride specifically for testing solutions during refining.
How to Test for Gold in Solution
Follow these steps carefully.
Step 1: Place a Drop of Solution on Filter Paper
Use a dropper or glass rod to place a small drop of the refining solution onto a piece of filter paper.
Filter paper helps make the reaction easier to see.
Step 2: Add Stannous Chloride
Add a small drop of stannous chloride solution to the sample.
The reaction will occur immediately if gold is present.
Step 3: Observe the Color Reaction
Watch for the following colors.
Purple or dark brown
Gold is present in solution.
Light purple or faint color
Very small amount of gold is present.
No reaction
No dissolved gold is detected.
When to Use the Stannous Chloride Test
Refiners typically test at several stages of the refining process.
After Dissolving Gold
Testing confirms the gold successfully dissolved into solution.
Before Precipitation
Testing ensures gold is present before adding precipitant.
After Precipitation
Testing the remaining liquid confirms that all gold has been recovered.
If no purple reaction occurs, precipitation was successful.
Common Testing Mistakes
Testing Dirty Solution
Solid particles can interfere with the reaction. Always test filtered solution.
Using Old Stannous Chloride
Stannous chloride degrades over time and may stop working.
Fresh solution provides the most reliable results.
Adding Too Much Test Solution
Only a small drop is needed. Too much reagent can make the reaction harder to see.
How Refiners Use This Test to Improve Gold Recovery
Stannous chloride testing allows refiners to track gold throughout the refining process.
By testing at each stage, refiners can:
• confirm gold dissolved correctly
• ensure precipitation worked
• detect leftover gold in solution
This prevents gold losses and improves overall recovery.
Recommended Gold Refining Supplies
If you're refining scrap gold, jewelry, or electronic components, using the correct chemicals and fresh reagents is critical for consistent results. These supplies are commonly used in the aqua regia gold refining process.
Hydrochloric Acid for Aqua Regia