Polyprotic

Many acids, however, are able to furnish more than one proton per molecule; these are known as polyprotic acids.

Some important acids, such as sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄) can furnish more than one proton and are called polyprotic acids.

Carbonic acid from CO₂ and amino acids from proteins are examples of polyprotic acids—those having more than one acidic proton.