precipitation of palladium with sodium metabisulfite

[arthur kierski]

i read in one of the threads yesterday,that a nitric solution containing pd could be precipitated with sodium metabisulfite-----i did the precipitation and obtained a yellow pd salt----
Question: how can i obtain pd from this yellow salt?
thanks and regards to all
Arthur

 

[9kuuby9]

The precipitated salt is Na2Pd(SO3)2x2H2O; Wash the Complex Pd salt ;

Dissolve the bright yellow Pd salt in excess ammonium hydroxide, filter and precipitate the canary yellow Pd ammonium chloride with HCl. This is the purified Pd salt we have made in the past. It gets converted to Pd metal via incineration or zinc in 5% HCl.

 

[freechemist]

Hi Arthur,

If it is really that yellow salt, Na₂Pd(SO₃)₂x2H₂O, what you have in hand, the procedure to recover metallic Pd out of it, is even more simple. Important prerequisites are, that no halide and no nitrate may be present. Thus, the salt has to be properly washed, using not too much water, since it is somewhat soluble, and the wash-water retains it's slight yellow coloration continuously. It can be reacted directly to metallic palladium simply, by heating in an excess of aqueous sulfuric acid. The active reductant for Pd(II) to Pd(0) is sulfurous acid or it's anhydride, sulfur dioxide, obtained through protonation of the sulfite-ligands contained in the complex-salt to be reduced.

[Pd(SO₃)₂]^2- + 4 H⁺ ==> Pd²⁺ + 2 H₂SO₃
Pd²⁺ + H₂SO₃ + H₂O => Pd(0)-metal + H₂SO₄ + 2 H⁺
H₂SO₃ ==> SO₂ + H₂O

Reduced this way, metallic Pd is obtained as a dense, grey powder, quite different from usually black and much finer powder, formed on reduction of Pd-salts with formic acid.

 

[arthur kierski]

thanks Freechemist,i will do what you wrote--------
Regards
Arthur