Platinum: Dissolve 0.100g platinum metal in a minimum volume of aqua regia and evaporate just to dryness. Add 5 ml conc. HCl and 0.1g NaCl and again evaporate just to dryness. Dissolve residue in 20 ml of 1+1HCl and dilute to 1000ml with water; 1.00ml=100ugPt.