# Too much Sulfuric acid in Rhodium plating bath



## tieungaogiangho09 (Apr 3, 2011)

I am now working with 10 litres of Rhodium plating solution ( 2Grs/L ). The sulphuric acid content in the bath is too much, about 100grs/L. I want to remove the excess sulphuric acid from this bath but, i do not know how to. Are there some ways to remove excess sulphuric acid from the Rhodium plating solution? Thanks for the helps.
Tieungao


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## arthur kierski (Apr 3, 2011)

i do this by making an naoh addition to make a yellow hydroxide----then i add h2so4 with water to dissolve the hidroxide and remake the rh sulphate solution----note:never done with 10liters(20grams of rh)--note2;this procedure is done with high quality reagents--here we call pro analysis lab reagents----
Arthur


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## Lou (Apr 3, 2011)

Arthur gave good advice. 

There is no other way to remove the sulfuric acid without employing some sort of cation exchange membrane. Given the low qty of solution you have, it's not worth doing that. If you had thousands of liters, then it'd be worth treatment.

I'd use sodium carbonate until pH 4, then go with NaOH til pH 8.


Lou


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## goldsilverpro (Apr 3, 2011)

Barium carbonate or, possibly, barium hydroxide? The barium sulfate should be quite insoluble and could be filtered out. Excess sulfuric is removed from chrome plating solutions using barium carbonate in very exacting amounts. Calcium salts might work also.


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## Lou (Apr 3, 2011)

Damn good correction GSP; I completely forgot, and I am shamed!  Barium, calcium, and strontium are all great to remove phosphate and sulfate. However, barium salts are pretty poisonous (sans the insoluble sulfate).


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