# insoluble rhodium salt



## arthur kierski (Aug 25, 2012)

i obtained an isoluble redish-brown salt(that i think it is rh salt)----i did many things to reduce this salt to black rh powder or to dissolve this salt to make a solution-----i did not obtained results---
i would like some help and ideas of how to treat this material
thanks in advance,
Arthur kierski
note: i incinerated tissue paper impregnated with rh sulfate (34kilos of paper was reduced to 1,2kilos) and i took a sample from this1,2kilos and made a fusion with nahso4 in an oven at 500centigrates for 2hours---when boiled this fusion with water,i did not dissolve rh in solution----and this grey powder became the redish-brown insoluble rh SALT??----
note2:could the incinerated tissue rh sulfate paper become rh2s3 and this is not dissolving in nahso4?
sorry for the long thread---i wanted to be explicit
regards
Arthur


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## butcher (Aug 25, 2012)

arthur kierski,

Of the heavier metals specific gravity 12 to 22, 
Several metals are not attacked in boiling hot Aqua regia (tantalum, iridium, rhodium, ruthenium),
Some metals are only slowly attacked (tungsten, platinum),
Some are attacked more rapidly attacked (gold, palladium, osmium).

Lets look at the metals not attacked in hot aqua regia, tantalum is attacked by hydrofluoric acid, (while rhodium iridium and ruthenium is not attacked by this dangerous acid).

A boil in sulfuric acid will attack rhodium, but will not attack iridium or ruthenium (these two metals have very different specific gravity which can be useful to help identify them)


Have you tried to boil in H2SO4 (few drops of HNO3), this should put Rh into solution, to dilute cool first and pour into water slowly.

Using Hydrofluoric acid is very dangerous and I am not recommending its use, (just giving a way to tell metals apart that will not dissolve in aqua regia), this acid will also attack glass.

Take every precaution with hot concentrated sulfuric is extremely unforgiving to skin eyes or clothing, if you do try and to use the information understand all of the safety precautions.


I am not sure what is going on, the sulfate fusion you tried should have put some metal into solution as a soluble reddish sulfate solution?
Are you sure this is Rhodium?


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## arthur kierski (Aug 26, 2012)

Thanks Butcher for your explanation---i did almost all the issues that you wrote in your explanations without results---even the hf attack---i obtained a tiny quantity of rh in the h2so4 attack and in the hf attack---but ,i think that the powder (redish brown) is still a rh salt---i am sure that the papers were impregnated with rhsulfate---
in one of my experiments i used a hcl boil of some of the incinerated paper----it released some h2s gas(rotten egg smell) and the liquid became red(pink) ,typical rhcl solution--i cemented this solution and obtained some rh powder---that made me think that after incineration of the tissue paper,rh2s3 was obtained ----thanks again for your explanations
Arthur
ps: from the 1,2kilos of grey incinerated paper, i still have 950grams , and 50grams of redish -brown(rh salt???)


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## Oz (Aug 26, 2012)

Arthur,
You have mentioned that this is a “salt” that you have incinerated, and yet still have a salt. I have to ask if you have taken this “salt” to a red heat and held it there as in classical calcination. You will likely form some Rh2O3, but you and I have discussed that in depth in the past.


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## arthur kierski (Aug 26, 2012)

Oz,i did incinerate the supposed salt and formed some rh2o3------ i received before impregnated tissue paper and did not have the problems that i am having with this last lot(34kilos)---
regards and all the best to you,
Arthur Kierski,your eternal friend


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