A medium having a high acidity, generally greater than that of 100 wt.% sulfuric acid. The common superacids are made by dissolving a powerful Lewis acid (e.g. SbF₅) in a suitable Brønsted acid such as HF or HSO₃F. (An equimolar mixture of HSO₃F and SbF₅ is known by the trade name 'magic acid'.) In a biochemical context 'superacid catalysis' is sometimes used to denote catalysis by metal ions analogous to catalysis by hydrogen ions. By analogy, a compound having a very high basicity, such as lithium diisopropylamide, is called a 'superbase'.