# Rhodium sulfate solution



## Ibex (Nov 9, 2021)

Hi everyone 
I have questions about rhodium sulfate solution, normally the solution is 99.97 or 99.95 % ,is there any chance to lower the purity of the rhodium to 99.00 or 98.5 ? 
Please advise


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## upcyclist (Nov 9, 2021)

Sure there is, but if you need it at 99.0%, you'll have to know exactly what it is right now to dilute it by the correct amount. Your end state is only as precise as your knowledge about it's current state.

And while your end _metal _might be 99.95% pure, that does not mean your _solution _is at a 99.95% concentration of Rh2(SO4)3. That would mean that 99.95% of the weight is rhodium sulfate, and only 0.05% is free sulfuric acid. I doubt that very much. The old bottles of plating solution were ~1 ozt/qt, so the buyer knew how much PM he was getting. Another example: when I have 300ml of a yellow gold chloride solution, and I've done everything right, I'll get some very pure gold powder out of it (hopefully .995 or better), but that has nothing to do with the amount of gold in the solution. I can't tell density from color very well, so there could have been 10g of gold in there, there could have been half a gram. I'll know when I precipitate, wash, dry, and weigh it. Until then, I can't tell you what % gold was in the solution. Density would probably be a more practical measure at that point anyway (g/ml3).


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## Ibex (Nov 9, 2021)

Thanks for your reply. Is it possible to exchange the number ? Any help appreciated


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## Lou (Nov 9, 2021)

You’re asking about using lower purity rhodium. Probably but it will be at the cost of the whiteness and evenness of deposit.


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## Ibex (Nov 10, 2021)

Yes exactly.


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## upcyclist (Nov 10, 2021)

If you are using it for plating, just use what you have. The Rh level in the solution will deplete as it is plated onto your substrate anyway, so your solution will pretty quickly drop below 99.5%.

One way to slow this down is to use a Rhodium anode, so that the Rh depletes from the anode instead of the solution. Except Rh is currently about $11k/ozt


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## Ibex (Nov 10, 2021)

Thanks for reply. 
Lets see


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