Testing for Rhodium

[lazersteve]

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

 

[Lou]

Excellent work Steve, I figured as much would come from your experimentation!!

So tell me, how did you do it, mix up the soluble RhCl3 with some Pd and Pt compounds?
Rather nice to have pure materials to work with, isn't it? Helps with making standards


Lou

 

[lazersteve]

Lou,

I started out learning the process with the known samples, then I moved on to testing my unknown complexes and odd colored (orange, rose, and red) powders that tested positive to stannous for Pt on a cotton swab.

The Rh you see in the left test tube above was the result of some experiments that I performed on some medical scrap. The Pt on the right was a flesh colored (very light tan-yellow like in Stefan's Tutorial) powder that I precipitated with NH4Cl from one of my cat tests.

I have many grams of assorted colored powders that I have produced while working with the cats and making the Pt and Pd DVD.

Learning this test has allowed me to identify no less than three solutions in my lab that contained Rh and two powders that I had previously produced.

I can not stress the importance of everyone knowing how to use your test solutions when refining. If I had not learned this test process, I may have tossed out three Rhodium containing solutions as barren. I'm constantly testing my solutions and powders as I work. I will never toss the baby out with the bath water as long as I'm adept at using my test solutions. :wink:

Steve

 

[eagle2]

Thank You Steve.

Its really helpful to see the exact shade of red that Rhodium produces.

Al

 

[4metals]

The moderators would like to thank all of the members that contributed to the original thread upon which this thread was based, as well as those that asked questions showing what was missing. Because of the extra length and interest in this thread we have created the above consolidated version making for an easier read. We encourage all members to read, comment, and ask questions in the original thread, Testing for Rhodium.

The Library threads should not be considered to constitute a complete education. Instead, they're more like reading a single book on the subject of recovery and refining. There is so much more information on the forum, and it is impossible to include it all in these condensed threads. Members are strongly encouraged to read the rest of the forum to round out their education.