Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Phase equilibria in the Mg(NO3)2 - Ln(NO3)3 (Ln = La, Ce, Pr) - HNO3 ( 21%) - H2O systems at 298.15 K and thermodynamic properties of 3Mg(NO3)2*2Ln(NO3)3*24H2O

Su, M.-Y.[Meng-Yao], Tang, Y.-F.[Yu-Feng], Qiao, Z.-P.[Zhan-Ping]
J. Chem. Thermodyn. 2017, 105, 289-295
ABSTRACT
The solid-liquid equilibria of the Mg(NO3)2-Ln(NO3)3 (Ln = La, Ce, Pr)-HNO3-H2O systems in the ( 21%) HNO3 regions at T = 298.15 K were studied by using the method of isothermal solubility, the phase diagrams were obtained based on the measured data. The Schreinemaker s wet residues method was used to determine the compositions of solid-phases. The three quaternary systems are all composed of three equilibrium solid-phases Mg(NO3)2*6H2O, 3Mg(NO3)2*2Ln(NO3)3*24H2O, Ln(NO3)3*6H2O. The new solidphase compounds 3Mg(NO3)2*2La(NO3)3*24H2O, 3Mg(NO3)2*2Ce(NO3)3*24H2O and 3Mg(NO3)2*2Pr (NO3)3*24H2O are congruently soluble in an average medium of 21 mass% HNO3, and they were characterized by chemical analysis, X-ray diffraction (XRD), X-ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric (TG-DTG) techniques. The XRD graphs of 3Mg(NO3)2*2La(NO3)3*24H2O, 3Mg(NO3)2*2Ce(NO3)3*24H2O and 3Mg(NO3)2*2Pr(NO3)3*24H2O are identical due to their isomorphic structure. The X-ray diffraction single crystal structure analysis show that 3Mg (NO3)2 2Ln(NO3)3 24H2O (Ln = La, Ce, Pr) all belong to hexagonal systems, with space group R3, for 3Mg(NO3)2*2La(NO3)3*24H2O, a = b = 1.1082 +- 0.0009 nm, c = 1.7422 +- 0.0013 nm, V = 1.853 +- 0.002 nm3, Dc = 3.976 g cm 3, Z = 3, for 3Mg(NO3)2*2Ce(NO3)3*24H2O, a = b = 1.1056 +- 0.0003 nm, c = 1.7438 +- 0.0009 nm, V = 1.8462 +- 0.0008 nm3, Dc = 3.997 g cm 3, Z = 3, for 3Mg(NO3)2*2Pr (NO3)3*24H2O, a = b = 1.0992 +- 0.0009 nm, c = 1.7211 +- 0.0007 nm, V = 1.8012 +- 0.0013 nm3, Dc = 4.101 g cm 3, Z = 3. The DsolHh m (standard molar enthalpies of solution) of the compounds 3Mg (NO3)2*2La(NO3)3*24H2O, 3Mg(NO3)2*2Ce(NO3)3*24H2O and 3Mg(NO3)2*2Pr(NO3)3*24H2O in water (aq) were measured to be (107.96 +- 0.74) kJ mol-1, (110.18 +- 0.54) kJ mol-1 and (102.96 +- 0.55) kJ mol-1, respectively, and their DfHh m (standard molar enthalpies of formation) were calculated to be (12242.6 +- 2.5) kJ mol-1, (12223.1 +- 2.4) kJ mol-1 and (12232.6 +- 2.5) kJ mol-1, respectively.
Compounds
# Formula Name
1 H2O water
2 MgN2O6 magnesium nitrate
3 LaN3O9 lanthanum(III) nitrate
4 N3O9Pr praseodymium nitrate
5 HNO3 nitric acid
6 H48La2Mg3N12O60 lanthanum magnesium nitrate hydrate (La2Mg3(NO3)12*24H2O)
7 Ce2H48Mg3N12O60 cerium magnesium nitrate hydrate (Ce2Mg3(NO3)12*24H2O)
8 H48Mg3N12O60Pr2 magnesium praseodymium nitrate hydrate (Pr2Mg3(NO3)12*24H2O)
9 CeN3O9 cerium nitrate
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 6
  • Mass density, kg/m3 ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • X-ray diffraction
  • 1
  • POMD
  • 7
  • Mass density, kg/m3 ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • X-ray diffraction
  • 1
  • POMD
  • 8
  • Mass density, kg/m3 ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • X-ray diffraction
  • 1
  • POMD
  • 5
  • 1
  • 2
  • Mass fraction - 2 ; Liquid
  • Mass fraction - 5; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Crystal of intercomponent compound 1
  • Titration method
  • 1
  • POMD
  • 5
  • 1
  • 3
  • Mass fraction - 3 ; Liquid
  • Mass fraction - 5; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Crystal of intercomponent compound 1
  • Titration method
  • 1
  • POMD
  • 5
  • 1
  • 9
  • Mass fraction - 9 ; Liquid
  • Mass fraction - 5; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Crystal of intercomponent compound 1
  • Titration method
  • 1
  • POMD
  • 5
  • 1
  • 4
  • Mass fraction - 4 ; Liquid
  • Mass fraction - 5; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Crystal of intercomponent compound 1
  • Titration method
  • 1
  • POMD
  • 1
  • 6
  • Molar enthalpy of solution, kJ/mol ; Liquid
  • Mole fraction - 6; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Calvet calorimetry
  • 1
  • POMD
  • 1
  • 7
  • Molar enthalpy of solution, kJ/mol ; Liquid
  • Mole fraction - 7; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Calvet calorimetry
  • 1
  • POMD
  • 1
  • 8
  • Molar enthalpy of solution, kJ/mol ; Liquid
  • Mole fraction - 8; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Calvet calorimetry
  • 1