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

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)

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

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

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

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