This has been discussed on a variety of forums lately. The consensus of the chemically knowledgable is that the regular platinum metal salt in solution effectively convetss the Na2 (pt IV) into regular platinum. This negates the restraining effect of the Na2. So it is not surprising that small dilutions of Na2 in conjunction with a lot of regular platinum in the solution renders it ineffective. Na2 ONLY works well with pure palladium prints. The reason you got fogging was that you were essentially printing with no contrast agent at all! Bottom line: if you want some platinum in your image, you gotta use another method of contrast control.