Published February 2017 | Version v1
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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

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Highlights: • Solubility was measured for Mg(NO3)2–Ln(NO3)3 (Ln = La, Ce, Pr)–HNO3–H2O (∼21%) + H2O systems at T = 298.15 K. • The corresponding phase diagrams were plotted. • Three new solid phase compounds 3Mg(NO3)2·2Ln(NO3)3·24H2O (Ln = La, Ce, Pr) were characterized. • ΔfHθm for three new solid phase compounds were determined. - 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 solid-phase 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 ΔsolHθm (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 ΔfHθm (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.

Availability note (English)

Available from http://dx.doi.org/10.1016/j.jct.2016.10.036

Additional details

Identifiers

DOI
10.1016/j.jct.2016.10.036;
PII
S0021-9614(16)30344-5;

Publishing Information

Journal Title
Journal of Chemical Thermodynamics
Journal Volume
105
Journal Page Range
p. 289-295
ISSN
0021-9614
CODEN
JCTDAF

INIS

Country of Publication
United Kingdom
Country of Input or Organization
International Atomic Energy Agency (IAEA)
INIS RN
49002228
Subject category
S37: INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; S36: MATERIALS SCIENCE;
Resource subtype / Literary indicator
Numerical Data
Descriptors DEI
EQUILIBRIUM; EXPERIMENTAL DATA; FORMATION HEAT; MAGNESIUM NITRATES; MONOCRYSTALS; NITRIC ACID; NITROGEN OXIDES; PHASE DIAGRAMS; SOLUBILITY; SOLUTION HEAT; SPACE GROUPS; THERMAL GRAVIMETRIC ANALYSIS; X RADIATION; X-RAY DIFFRACTION
Descriptors DEC
ALKALINE EARTH METAL COMPOUNDS; CHALCOGENIDES; CHEMICAL ANALYSIS; COHERENT SCATTERING; CRYSTALS; DATA; DIAGRAMS; DIFFRACTION; ELECTROMAGNETIC RADIATION; ENTHALPY; GRAVIMETRIC ANALYSIS; HYDROGEN COMPOUNDS; INFORMATION; INORGANIC ACIDS; INORGANIC COMPOUNDS; IONIZING RADIATIONS; MAGNESIUM COMPOUNDS; NITRATES; NITROGEN COMPOUNDS; NUMERICAL DATA; OXIDES; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; QUANTITATIVE CHEMICAL ANALYSIS; RADIATIONS; REACTION HEAT; SCATTERING; SYMMETRY GROUPS; THERMAL ANALYSIS; THERMODYNAMIC PROPERTIES

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Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.