Tuesday Safety Talk: Aqua Regia & Piranha Acid

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

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