Metal surface treatment agent, phosphate raw material products, organic catalysts, refractory additives, wood raw material to manufacture activated carbon-activated agent
Pure anhydrous phosphoric acid is a white solid that melts at 42.35 °C to form a colorless, viscous liquid. Pure 75-85 percent aqueous solutions (the most common) are clear, colorless, odorless, non-volatile, rather viscous, syrupy liquids, but still pourable.
Most people and even chemists simply refer to orthophosphoric acid as "phosphoric acid," which is the IUPAC name for this compound. The prefix ortho- usually is used when one wants to distinguish it from other phosphoric acids called polyphosphoric acids. Orthophosphoric acid is a non-toxic, inorganic, rather weak triprotic acid which, when pure, is a solid at room temperature and pressure. The chemical structure of orthophosphoric acid is shown in the data table.
Orthophosphoric acid is a very polar molecule, therefore it is highly soluble in water. The oxidation state of phosphorus (P) in ortho- and other phosphoric acids is +5; the oxidation state of all the oxygens (O) is -2 and all the hydrogens (H) is +1. Triprotic means that an orthophosphoric acid molecule can dissociate up to three times, giving up an H+ each time, which typically combines with a water molecule, H2O, as shown in these reactions:
- H3PO4(s) + H2O(l) ? H3O+(aq) + H2PO4–(aq) Ka1= 7.5×10−3
- H2PO4–(aq)+ H2O(l) ? H3O+(aq) + HPO42–(aq) Ka2= 6.2×10−8
- HPO42–(aq)+ H2O(l) ? H3O+(aq) + PO43–(aq) Ka3= 2.14×10−13