The Raman spectra of ortho-phosphoric acid and some phosphates
The Raman spectra of ortho-phosphoric acid for a wide range of concentrations and of the primary, secondary and tertiary phosphates of sodium, potassium and ammonium have been obtained. The acid has yielded new lines which indicate the ionisation of H3PO4→H°+H2PO4′ and the further ionisation of H2PO4→H°+HPO4″. Weak lines characteristic of the OH oscillations have also been observed for the acid. The three series of phosphates give characteristic spectra which are identified as due to H2PO4′,HPO4″ and PO4‴ ions. The frequency shifts of the PO4 radical are compared with those of SO4 and SeO4 and the force constants are evaluated.