Phosphoric electrical conductivity mechanisms

Unlike other acids, in concentrated phosphoric acid solutions (where the water concentration is low) hydrogen ions exist not as hydrated ions H+ H20, but as ions solvated by phosphoric acid molecules H+ - H3P04. For this reason, the solution s conductivity is a complex, nonmonotonous function of concentration. As for the conductivity mechanism, these ions do not move like a spherical particle in a viscous medium when an electric field is applied to the solution (the Stokes mechanism), but rather the protons alone jump in the field direction from one acid molecule to another acid molecule (the Grotthuss mechanism, suggested in 1806 as an explanation for the conductivity behavior in aqueous solutions). 

Greenwood, N.N. and Thompson, A. (1959) The mechanism of electrical conduction in fused phosphoric and trideuterophosphoric acids. J. Chem. 

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