Mélange piranha

Piranha solution, also known as piranha etch, is a mixture of sulfuric acid () and hydrogen peroxide (). The result of the mixture gives rise to a strong union of two acids called per-hexa-sulfuric acid (H4SO6) that is used to clean organic residues off substrates. Because the mixture is a strong oxidizing agent, it will decompose most organic matter, and it will also hydroxylate most surfaces (by adding –OH groups), making them highly hydrophilic (water-compatible). This means the solution can also easily dissolve fabric and skin, potentially causing severe damage and chemical burns in case of inadvertent contact. It is so named after the fish, piranha. Many different mixture ratios are commonly used, and all are called piranha. A typical mixture is 3 parts of concentrated sulfuric acid and 1 part of hydrogen peroxide solution; other protocols may use a 4:1 or even 7:1 mixture. A closely related mixture, sometimes called "base piranha", is a 3:1 mixture of ammonia solution (, or ) with hydrogen peroxide. As hydrogen peroxide is less stable at high pH than under acidic conditions, (pH c. 11.6) also accelerates its decomposition. At higher pH, will decompose violently. Piranha solution must be prepared with great care. It is highly corrosive and an extremely powerful oxidizer. Surfaces must be reasonably clean and completely free of organic solvents from previous washing steps before coming into contact with the solution. Piranha solution cleans by decomposing organic contaminants, and a large amount of contaminant will cause violent bubbling and a release of gas that can cause an explosion. Piranha solution should always be prepared by adding hydrogen peroxide to sulfuric acid slowly, never in reverse order. This minimises the concentration of hydrogen peroxide during the mixing process, helping to reduce instantaneous heat generation and explosion risk. Mixing the solution is an extremely exothermic process. If the solution is made rapidly, it will instantly boil, releasing large amounts of corrosive fumes.