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