The standard enthalpy of formation of anhydrous, monohydrated, and dihydrated zirconium bis(monohydrogenphosphate)

The enthalpies of solution of amorphous and crystalline Zr(HPO4)2 · H2O, of Zr(HPO4)2, and Zr(HPO4)2 · 2H2O have been measured calorimetrically and the standard enthalpies of formation derived. The results obtained are as follows: ΔHfo(s, 298.15 K)/kJ mol−1Zr(HPO4)2 · H2O(am)−3435.8 ± 4.2Zr(HPO4)2 · H2O(c)−3463.7 ± 4.1Zr(HPO4)2(c)−3167.9 ± 4.1Zr(HPO4)2 · 2H2O(c)−3741.2 ± 4.1