Standard heats of formation of two sodium pyrophosphates, sodium trimetaphosphate, and sodium tetrametaphosphate
Abstract
The standard heats of formation of Na2H2P2O7, Na4P2O7, (NaPO3)3 and (NaPO3)4 have been determined by solution calorimetry. The values obtained at 298°K are: ΔH°fNa2H2P2O7(c)=–664.7±1.0 kcal/mole–1; ΔH°f Na4P2O7(c)=–763.7±1.0 kcal/mole–1; ΔH°f(NaPO3)3(c)=–878.6±1.5 kcal mole–1; ΔH°f(NaPO3)4(c)=–1169.4±2.0 kcal mole–1.