Dihydrogen sulfate or H2SO4 is a rarely used chemical name for sulfuric acid. Although the term is technically correct, most sources of chemical information only list the acid under its common name.
Sulfuric acid is commonly used in agricultural fertilizers, but it can interact with most organic compounds. The concentrated acid has a high affinity for water and can also be used to dehydrate materials. Although it is always true that one should add acid to water rather than vice versa, care should always be taken when diluting sulfuric acid. The exothermic reaction that occurs when sulfuric acid interacts with water releases enough heat that it may cause the mixture to boil. Therefore, it's essential to dilute the acid slowly and stir regularly.