Process of Platinization of Platinum Metal
Before platinization, the platinum surface is cleaned by immersion in aqua regia (50% solution, i.e., 3 volumes of 12 mol/kg of HCl, 1 volume of 16 mol/kg HNO3, 4 volumes of water).
Platinization is often conducted from water solution of 0.072 mol/kg of chloroplatinic acid and 0.00013 mol/kg of lead acetate, at a current density of 30 mA/cm2 for up to 10 minutes. The process evolves chlorine at the anode; the interaction of the chlorine with the cathode is prevented by employing a suitable separation (e.g., a glass frit).
Another author recommends electroplating with the current density of 5 mA/cm2 while reversing the polarity every 30 s for 15 minutes.
After platinization, the electrode should be rinsed and stored in distilled water. The electrode loses its catalytic properties on prolonged exposure to air.
Read more about this topic: Platinum Black
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