Phosphoric acid (H?PO?) is a colorless, transparent crystalline solid at room temperature, with a melting point of 42 °C. When the temperature exceeds its melting point, it becomes a colorless, transparent viscous liquid. In industrial and laboratory settings, phosphoric acid is commonly available as an 85% aqueous solution, which is a colorless, odorless, non-volatile, viscous liquid and serves as an important chemical reagent. As a moderately strong triprotic acid, phosphoric acid can release three protons stepwise, forming three different protonated forms: H?PO??, HPO?2?, and PO?3?. This property gives it significant versatility in chemical reactions.