Tuesday Safety Talk: Aqua Regia & Piranha Acid

1. Tuesday Safety Talk:Aqua Regia & Piranha Acid Eric Silver Sessler Group Safety Talk January 15, 2013

2. When to use? • To remove metal residues (Both) • To remove noble metals (Aqua regia) • To remove organic residues (Both) • To remove carbon residues (Piranha Acid) • To clean glass fritted filters (Piranha Acid)

3. Recipes • Aqua regia– 1 part conc. HNO3 + 3 parts conc. HCl • Piranha acid – 3 parts conc. H2SO4 + 1 part H2O2 (30% or less) • 50% H2O2 or greater can lead to explosions

4. Use • Aqua regia – Always add HNO3 SLOWLY TO HCl • Piranha acid – Always add H2O2 SLOWLY TO the H2SO4 • Wear proper PPE – Safety goggles, lab coat and black neoprene gloves • Prepare solutions in the hood • Make sure the glassware is completely dry before adding either solution

5. Precautions • Allow the acids to react overnight, due not store hot • Both are exothermic reactions • Aqua regia produces NO and Cl2 gas • Both solutions are HIGHLY CORROSIVE • Keep away from solvents and plastics

6. Disposal • Aqua regia – a) Carefully neutralize with NaHCO3 and pour down drain or b) Store in properly labeled glass container • Piranha acid – a) Allow to cool down then carefully neutralize with NaHCO3 and pour down the drain or b) Store in properly labeled glass container • Do not dispose with organic solvents