Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is a weak acid with the chemical formula H3PO4. The pure compound is a colorless solid. All three hydrogens are acidic to varying degrees and can be lost from the molecule as H+ ions (protons). When all three H+ ions are removed, the result is an orthophosphate ion PO43−, commonly called “phosphate”. Removal of one or two protons gives dihydrogen phosphate ion H2PO−4, and the hydrogen phosphate ion HPO2−4, respectively. Orthophosphoric acid also forms esters, called organophosphates. Phosphoric acid is commonly encountered in chemical laboratories as an 85% aqueous solution, which is a colorless, odourless, and non-volatile syrupy liquid. Although phosphoric acid does not meet the strict definition of a strong acid, the 85% solution can still severely irritate the skin and damage the eyes.

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