Diffusion coefficients for the ternary system Ca(OH)2–H3PO4–water

Abstract

A conductimetric method has been used to measure the ternary diffusion coefficients of calcium hydroxide–phosphoric acid in dilute aqueous solution at 25 °C. Diffusion coefficients for concentrated solutions of the electrolytes are evaluated from previously reported Gouy optical data for the related system Ca(H₂PO₄)₂–H₃PO₄–water. The experimental results indicate strong electrostatic coupling between diffusive flows of aqueous Ca(OH)₂ and H₃PO₄. The implications for dissolution of calcium hydroxyapatite, the main constituent of bone and teeth, are discussed.