Aluminum dihydrogen tripolyphosphate: Thermodynamic characteristics

For the first time solution enthalpies of Al, H3PO4, and AlH2P3O10 × 2H2O in 2 mol dm−3 NaOH have been measured as following: ΔsolH°1 = −404.75 ± 4.36 kJ mol−1; ΔsolH°2 = −189.48 ± 0.54 kJ mol−1; ΔsolH°3 = −238.95 ± 3.32 kJ mol−1. On the basis of experimental data the standard molar enthalpy of formation and enthalpies of some reactions with participation of AlH2P3O10 × H2O were calculated. The enthalpy of interaction of Al with H3PO4 is ΔrH° = −734.24 ± 5.56 kJ mol−1. It was established that according to thermodynamic data Al2O3 can react with H3PO4 forming investigated compound at 513 K. Employed compound (AlH2P3O10 × H2O) can react with H2O with formation of AlPO4 and phosphorous acid. All the data were obtained for the first time.