Volume indicated comprises equal amounts of Ferric Oxalate (FO) and palladium solution (Pd) to which is added 1 drop of the indicated concentration of Na2 solution. For most papers I also add 1 drop of Tween 20 per 1 ml of solution.
Example: 2ml = 1ml FO + 1ml Pd + 1 drop 5% Na2 + 2 drops Tween 20
J Keith Schreiber 