Piranha Solution

Piranha solution is a 3: 1 mixture concentrated sulfuric acid and hydrogen peroxide. There is also 
a “Base Piranha” which is composed of a 3: 1 mixture of ammonium hydroxide and hydrogen peroxide. 
The acid piranha ‘s reaction is self‐starting, and the base piranha requires heated before the 
reaction is initiated. Piranha is used to clean residue off substrates. It is extremely deleterious 
to skin or eyes, resulting in severe burns. Vapors are corrosive to mucous membranes and the upper 
respiratory tract.  While this solution is highly corrosive, it’s reactivity increases its risk for inadvertent
harm.
 

Sulfuric acid and peroxide mixtures are extremely exothermic. When added to one another significant 
off gassing occurs for up to 24‐26 after mixing and, in some situations, can result in the reaction 
vessel overflowing. Containers of newly mixed solution, if sealed during this period can 
over‐pressurize and explode. Because sulfuric acid and peroxide tend to stratify, when the 
container is moved or agitated heating and off‐gassing will again occur.

Piranha Solution is a very strong oxidizer when in contact with organic compounds. If containers 
are contaminated or a spill occurs resulting in piranha
solution mixing with organic material, it can cause an explosion.

UK Environmental Quality Management Department (EQMD) picked up a Piranha waste container from a 
research facility which then exploded in their facility after housing it for three days. The cause 
could not be determined but it was suspected the container was either contaminated or had not been 
mixed well. In either case, transport added enough energy to create off‐gassing and 
over‐pressurization of the container.

Work practices for the use of Piranha solution:
•  Always use glass (Pyrex® is preferred) containers. The solution can degrade plastic 
containers.
•  Ensure all containers are properly labeled to identify those containing piranha
acid solutions.

•  Always mix the solution in a chemical fume hood
•  Always add hydrogen peroxide to sulfuric acid while gently stirring. DO NOT add sulfuric acid to 
hydrogen peroxide.
•  Piranha solution will become very hot with temperatures exceeding 100°C during preparation. 
Handle with care to avoid thermal burns.
•  Do not mix piranha solution with incompatible materials such as organic acids, organic solvents, 
or other organic materials. Do not mix with bases (e.g., Photoresist). Mixing piranha with 
incompatible materials can lead to an explosion.
•  When submerging items in piranha baths, place items in the piranha solution slowly and 
carefully. The solution needs time to stabilize after each item is added. Apply piranha solution to 
substrates carefully as well.
•  NEVER TIGHTLY CAP piranha solutions. To prevent pressure build up, a vented cap should be 
used.

A lab coat, safety glasses and chemically compatible gloves (e.g., latex, butyl) gloves should be 
used when working with Piranha. If procedures involve anticipated splash or use large quantities, a 
rubber apron and safety goggles shall be used. ALL work with Piranha solution will be conducted 
within a certified chemical fume hood. All research labs utilizing Piranha shall maintain 
laboratory specific Standard Operating Procedures (SOP) for its safe use in the lab’s specific 
Chemical Hygiene Plan (CHP). All personnel using Piranha shall be properly trained in its use, with 
its documentation maintained in
e lab’s specific CHP.