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Piranha solution, also known as piranha etch, is a mixture of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2), used to clean organic residues off substrates. Because the mixture is a strong oxidizing agent, it will remove most organic matter, and it will also hydroxylate most surfaces (add OH groups), making them highly hydrophilic (water-compatible). ==Preparation and use== 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 30% 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 ammonium hydroxide (NH4OH) with hydrogen peroxide. 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 wash steps before coming into contact with piranha solution. Piranha solution cleans by dissolving organic contaminants, and a large amount of contaminant will cause violent bubbling and a release of gas that can cause an explosion.〔(【引用サイトリンク】accessdate=4 May 2011 )〕 Piranha solution should always be prepared by adding hydrogen peroxide to sulfuric acid very slowly, never in reverse.〔(【引用サイトリンク】Princeton University "> Section 10: Chemical Specific Information — Piranha Solutions )〕 Mixing the solution is extremely exothermic. If the solution is made rapidly, it will instantly boil, releasing large amounts of corrosive fumes. Even when made with care, the resultant heat can bring solution temperatures above 100 °C. It must be allowed to cool reasonably before it is used. The sudden increase in temperature can also lead to violent boiling of the extremely acidic solution. Solutions made using hydrogen peroxide at concentrations greater than 50% may cause an explosion. Once the mixture has stabilized, it can be further heated to sustain its reactivity.〔(【引用サイトリンク】 url = http://www.ch.cam.ac.uk/sites/ch/files/users/meg27/DSO017C%20Acid%20Piranha%20Solution%200911.pdf )〕 The hot (often bubbling) solution cleans organic compounds off substrates and oxidizes or hydroxylates most metal surfaces. It is strong enough to dissolve elemental carbon. Cleaning usually requires about 10 to 40 minutes, after which the substrates can be removed from the solution. The solution may be mixed before application or directly applied to the material, applying the sulfuric acid first, followed by the peroxide. Due to the self-decomposition of hydrogen peroxide, piranha solution should be used freshly prepared. Piranha solution should not be stored, as it generates gas and therefore cannot be kept in a closed container.〔 name="princeton"〕 As piranha solution reacts violently with many items commonly disposed of as chemical waste if the solution has not neutralised, it must be left in clearly marked containers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Piranha solution」の詳細全文を読む スポンサード リンク
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