Hydrogen sulfate, also known as bisulfate, is an ion. Its chemical formula is HSO4-. Chemical compounds containing this ion are known as bisulfates or hydrogen sulfates. An example would be sodium bisulfate. Hydrogen sulfates are acidic. They can be used as a weaker form of acid than sulfuric acid. It is a salt of sulfuric acid. In these compounds, sulfuric acid is deprotonated once. In the sulfate ion, it is deprotonated twice.