Testing for Rhodium

1. Add a drop of the solution (which contains no gold, pt, or pd) to be tested to a test tube with three drops of water. If testing a solid complex transfer a few grains of the complex into the test tube using a clean cotton swab.
2. Add 1 drop of stannous chloride solution to the sample.
3. A color change may occur which indicates platinum or palladium (yellow-orange to blue-green) when the stannous is added to a complex dissolved in water. This should not adversely affect the test, but you will need to become familiar with this condition to properly judge the Rhodium content of the solution/complex when Rhodium is also present.
4. Heat the test tube for a few moments over a heat gun on low or a Bunsen burner. DO NOT overheat as the liquid may bump out of the test tube!
5. If the solution is free of Pt and Pd you will see a golden yellow-orange color appear when the solution warms. If Pt or Pd are present the colored solutions will lighten towards golden yellow-orange when it warms. Typically 10-20 seconds of heating are required to reach this point.
6. Remove the test tube from the heat source when the color changes as mentioned above.
7. As the solution cools the color will change to a deep red color, between rose red and blood red depending on the Rhodium concentration.
8. Test detects 6ug (micro grams) per mL concentrations and greater of Rhodium in solution.

blueduck said:

I knew we had discussed this before, I have an hard rock ore body that is complex and reads high in Rh in a recent assay. Now to find a suitable leach to put Rh into solution (am searching the forum before asking for duplicate responses)

William
Idaho

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lazersteve said:

All,

Last night I did some experimenting with some Rhodium samples I have. I researched some literature and found a fairly easy way to test for Rhodium in solution and it also works for unknown complexes that are soluble in water or acid.

1. Add a drop of the solution (which contains no gold, pt, or pd) to be tested to a test tube with three drops of water. If testing a solid complex transfer a few grains of the complex into the test tube using a clean cotton swab.
2. Add 1 drop of stannous chloride solution to the sample.
3. A color change may occur which indicates platinum or palladium (yellow-orange to blue-green) when the stannous is added to a complex dissolved in water. This should not adversely affect the test, but you will need to become familiar with this condition to properly judge the Rhodium content of the solution/complex when Rhodium is also present.
4. Heat the test tube for a few moments over a heat gun on low or a Bunsen burner. DO NOT overheat as the liquid may bump out of the test tube!
5. If the solution is free of Pt and Pd you will see a golden yellow-orange color appear when the solution warms. If Pt or Pd are present the colored solutions will lighten towards golden yellow-orange when it warms. Typically 10-20 seconds of heating are required to reach this point.
6. Remove the test tube from the heat source when the color changes as mentioned above.
7. As the solution cools the color will change to a deep red color, between rose red and blood red depending on the Rhodium concentration.
8. Test detects 6ug (micro grams) per mL concentrations and greater of Rhodium in solution.

I have verified this test works and have learned how to identify Rhodium complexes and solutions even when Pt and Pd are present. It takes a little practice, with known control solutions, but it's not difficult to learn. I'm going to produce a video of the testing procedure and post it on my website soon.

Here's a photo of the test results:

The vial on the left is positive for Rhodium and the one on the right is positive for Platinum, both were tested with ordinary stannous chloride.

Steve

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