Standard heats of formation of NaH2PO4, Na2HPO4 and Na3PO4

Abstract

The standard heats of formation of NaH₂PO₄, Na₂HPO₄and Na₃PO₄ have been determined by solution calorimetry using reaction schemes involving aqueous NaOH and aqueous H₃PO₄. The values obtained are: ΔH^°_f298 NaH₂PO₄(c)=–369.0±0.5 kcal mole^–1, ΔH^°_f298 Na₂HPO₄(c)=–419.4±0.5 kcal mole^–1, ΔH^°_f298 Na₃PO₄(c)=–459.7±0.5 kcal mole^–1.