Behaviour of some inorganic phosphates in strongly acidic solvents studied by phosphorus-31 nuclear magnetic resonance spectroscopy

Abstract

We report the study, by ³¹P n.m.r., of phosphates in 100% sulphuric acid, chlorosulphuric acid, and a range of oleums containing up to 65% sulphur trioxide. In 100% sulphuric acid only one ³¹P n.m.r. signal identified as P(OH)₄⁺, is seen. In oleums beyond 12·5% SO₃, two signals are always seen, the δ values of which shift markedly with SO₃ concentration in the oleum. The causes of this shift are discussed in terms of the rapid equilibria of condensed phosphate species.