I did not mean to imply that you wouldn't get platinum in the image, only that if you decide to put regular pt(II) metal salt in your metal component, that it would negate the contrast control effects of the Na2 (PT(IV)), at least according to the information provide by Howard Efner.

I normally print in pure palladium, so this is a non-issue with me. But I realize a lot of people might normally use say, a 25% pt & 75% pd metal proportion, and that the presence of the pt(II) was problematic in its effect on the contrast control offered by Na2. Like you, I am not entirely clear about the reason.