Sodium chloroplatinate (Na2) is used as a contrast agent (more highlight inhibitor) for palladium printing. It works both with Na and Li palladium(II) salts but when I tested it with the ammonium salt (NH4)2[PdCl4] a precipitate forms instantaneously. I tested Na2 with a drop of fresh ammonium citrate developer and the same precipitate forms. Ammonium citrate is recommended as a standard developer for the Na2 method (even sold as a kit with Na2 by B&S). So I am somewhat baffled why it should work with that developer.