|MadSci Network: Chemistry|
Hi Thomas, Generally no. Strong mineral acids such as HCl, HBr, HNO3, HClO4 all have significant vapor pressures in aqueous solution and will evaporate away when boiled. Sulfuric acid that is free of water is made by hydrolysis of pyrosulfuric acid which is the product of sulfuric acid and SO3. Pure sulfuric acid boils at much higher temperature than water but the various hydrates of sulfuric acid boil at lower temperatures and would boil away without leaving behind any unhydrated sulfuric acid. Weaker acids such as acetic and trifluoroacetic can be purified by fractional distillation. Still other acids like tosyl acid (a stronger acid than HCl) and benzoic acid can be recrystallized because they are solids. Acids, as a class, are not prone to explode when heated. A strong acid may explode when water is added to it because the heat released upon hydration of the acid causes the water to vaporize rapidly. This is why dilution of acid must always be done by slow addition of the acid to water (not the reverse). HOWEVER, heating of strong acids will release dangerous fumes into the air!!! Particularly HClO4 vapor will deposit explosive residues wherever it goes. Another way to cause an "explosion" with a strong acid is to mix it with a strong base. Drano, and other similar products, are composed of strong bases in concentrated aqueous solution. One can also buy something at hardware stores called "concentrated drain opener" which is essential pure sulfuric acid. If one happened to own both products and tried to use them together to unclog the drain a disaster would result!! Strong acids should only be used in a well equipped laboratory and all industrial and academic labs have ready access to concentrated acids at cheap prices through commercial vendors. Thus, I would strongly discourage anyone from attempting to make a concentrated acid from a dilute acid, even in a lab. Jeremy.
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