Piranha solution consists of:
(1) 3 parts concentrated sulfuric acid
(2) 1 part 30% hydrogen peroxide (35% w/v)
It is prepared fresh just before use.
Hazards are related to:
(1) oxygen generation during use
(2) exothermic heat during preparation
(3) explosivity
(4) strong acidity
Precautions:
(1) Prepare in a strong and extremely clean glass containers. It may dissolve some plastic containers.
(2) Do not store in a closed container since oxygen gas is produced.
(3) Prepare and use in an acid hood. The fumes can be highly corrosive.
(4) Prepare and use wearing full body protection for handling strong acids.
(5) Add the hydrogen peroxide slowly to the acid while gently stirring. Do not add the acid to the hydrogen peroxide.
(6) The solution can become very hot when it is being prepared.
(7) The solution should be clearly marked.
(8) Items placed into the solution should be carefully precleaned. The presence of excessive organic contaminants can trigger a violent reaction.
(9) Use of a peroxide stock solution greater then 50% can be very dangerous and use of any solution over 30% should be avoided.
(10) Contact with organic solvents such as acetone can result in an explosion.
(11) The solution reacts with metal or non-Teflon polymers. Teflon-coated tweezers can be used.
(12) Dispose of very carefully. It should be left in an open container overnight or longer. It should be disposed of as hazardous waste. It should not be mixed with other solutions. The container should be very clean and have a vented cap.
(13) Some people will try to neutralize small volumes. This requires that the solution be first diluted with water (9 parts water to 1 part piranha solution). Sodium hydroxide or sodium carbonate can be added slowly and carefully. This is an exothermic reaction and an ice bath may be necessary to prevent overheating.
(14) Anything exposed to the solution needs to be copiously washed with distilled water.
(15) Anyone preparing or using the solution should be carefully trained prior to use.
