(Source : Working with Alternative Processes - Peter Marshall)
Stock solution
1 g of Potassium chloroplatinate* in 5 ml water
Working sol.
Water 350 ml
Sodium chloride 1 g
Citric acid 3 g
Platinum stock sol. 0.5 ml
Tone, then wash and treat in bath of sodium chloride and sodium carbonate (salt & soda). Wash.
Can be used following gold toning.
*CAUTION : Potassium chloroplatinate - also called Potassium hexachloroplatinate (IV) - is toxic.