Ammonium Oxalate

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Keshra Sangwal - One of the best experts on this subject based on the ideXlab platform.

  • Solubility of Ammonium Oxalate in water-acetone mixtures and metastable zone width of their solutions
    Chemical Engineering Research and Design, 2014
    Co-Authors: Keshra Sangwal, Ewa Mielniczek-brzóska, Sylwia Barylska
    Abstract:

    Abstract Experimental results on the solubility c of Ammonium Oxalate in mixed water–acetone solvents containing acetone content x T are presented and discussed using the theory of regular solutions. It was found that: (1) the dependence of the solubility c of Ammonium Oxalate in solutions of different mixed water–acetone solvents on temperature T follows an Arrhenius-type relation, (2) the dependence of c on acetone content x at different temperature T follows the relation: ln( c  +  δ ) =  a  −  bx , where the parameters a and b are measures of deviation of a solution from ideality and the correction factor δ is related to the activity coefficient f a of the solution, which decreases with an increase in c , and (3) the dependence of the solubility c of Ammonium Oxalate in solutions of different compositions x of water–acetone mixtures is related to the dielectric constant ɛ * of the solvent mixture, following the relation ln  c  =  C  +  C 1 ɛ *, where C and C 1 are related to the parameters a and b , respectively. Study of the metastable zone width, defined as maximum undercooling Δ T max a solution saturated at a particular temperature T can withstand, of some selected solutions of mixed water–acetone solvents at different T revealed that Δ T max decreases with an increase in antisolvent content x . The results are discussed using the self-consistent Nývlt-like approach.

  • Study of the nature of Cu(II) complexes in aqueous Ammonium Oxalate solutions by ultraviolet-visible spectroscopy
    Journal of Physics: Conference Series, 2011
    Co-Authors: Ewa Mielniczek-brzóska, Keshra Sangwal
    Abstract:

    Experimental results of an investigation of aqueous Ammonium Oxalate solutions containing Cu(II) impurity by ultraviolet–visible spectroscopy are described and discussed from the standpoint of speciation of complexes. The results show that absorption of light by aqueous Ammonium Oxalate solutions containing Cu(II) impurity in the range −5 < ln(ci/c) < 2.5 of the ratio of concentrations ci and c of impurity and solute, respectively, leads to decrease or increase in the intensity of bands of the ultraviolet–visible spectral regions, and these changes may be expressed by full width at half maximum, molar extinction coefficient, peak wavelength and oscillator strength. The changes are caused by the coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex, and are related with the impurity–solute concentration ratio ci/c. The coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex in the range 0 < ln(ci/c) < 2.5 leads to the formation of Cu(C2O4) complex, but the coordination of the C2O42− ligand with Cu(C2O4) complex in the concentration ratio range −5 < ln(ci/c) < 0 results in the formation of predominantly Cu(C2O4)22− complex. The effect of successive coordination of the C2O42− ligand is well-defined in the ultraviolet spectral region but poor in the visible region.

  • Investigation of metastable zone width of Ammonium Oxalate aqueous solutions
    Crystal Research and Technology, 2009
    Co-Authors: Keshra Sangwal, K. Wójcik
    Abstract:

    The metastable zone width of pure Ammonium Oxalate aqueous solutions, as represented by maximum supercooling ΔTmax, is investigated as functions of cooling rate R and saturation temperature T0 by the polythermal method. The experimental results are discussed by using two recently advanced approaches: (1) self-consistent Nývlt-like approach based on a power-law relationship between nucleation rate J and maximum supersaturation lnSmax, and (2) a novel approach based on the relationship between J and lnSmax described by the classical three-dimensional nucleation theory. Analysis of the experimental data revealed that both approaches describe the experimental data on metastable zone width by the polythermal method reliably and provide useful information about the physical processes and parameters involved in nucleation kinetics. The values of various physical quantities predicted by both of these approaches are reasonable for a fairly-soluble compound. A careful examination of the data on ΔTmax as a function of T0 obtained by polythermal method and from density measurements showed that ΔTmax has a slight tendency to decrease with increasing saturation temperature T0. The values of lnSmax at saturation temperature 303 K suggest that the metastable zone width of Ammonium Oxalate aqueous solutions is determined by primary nucleation in the polythermal method and by secondary nucleation during density measurements. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  • Study of copper complexes in saturated and unsaturated aqueous Ammonium Oxalate solutions containing Cu(II) impurity
    Fluid Phase Equilibria, 2007
    Co-Authors: Keshra Sangwal, Ewa Mielniczek-brzóska
    Abstract:

    Abstract The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated Ammonium Oxalate (AO) aqueous solutions was investigated as a function of concentration c i of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of Ammonium Oxalate containing Cu(II) ions the following species are formed: Cu 2+ , Cu(OH) + , Cu(OH) 2 , CuC 2 O 4 0 and Cu(C 2 O 4 ) 2 2− in addition to C 2 O 4 2− , HC 2 O 4 − , H 2 C 2 O 4 and (NH 4 ) 2 C 2 O 4 0 species, and their concentration depends on concentrations c i of Cu(II) impurity and c of Ammonium Oxalate. The dependences of solution pH and of absorbance A and the corresponding wavelength λ for unsaturated aqueous solutions on Ammonium Oxalate concentration c containing different concentrations c i of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c . Speciation analysis revealed that Cu 2+ and CuC 2 O 4 0 , CuC 2 O 4 0 and Cu(C 2 O 4 )2 2− , and Cu(C 2 O 4 ) 2 2− complexes are predominantly present in the solute concentration intervals c ≤ 0.01  mol/dm 3 , 0.01 mol/dm 3 c 0.03  mol/dm 3 and c ≥ 0.03  mol/dm 3 , respectively. The concentration interval range 0.01 mol/dm 3 c 0.03  mol/dm 3 corresponds to the pH interval where Cu(OH) 2 is precipitated. It was found that the solubility of Ammonium Oxalate at 30  ° C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of Ammonium Oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C 2 O 4 ) 2 2− -type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC 2 O 4 0 and Cu(C 2 O 4 ) 2 2− species.

  • Effect of cationic impurities on solubility and crystal growth processes of Ammonium Oxalate monohydrate: Role of formation of metal‐Oxalate complexes
    Crystal Research and Technology, 2007
    Co-Authors: Keshra Sangwal, Ewa Mielniczek-brzóska
    Abstract:

    The effect of different bi- and trivalent cationic impurities on the solubility of Ammonium Oxalate and the composition and distribution of chemical complexes formed in saturated Ammonium Oxalate aqueous solutions as a function of impurity concentration are investigated. The knowledge of the composition and stability of complexes formed in saturated aqueous solutions is then employed to explain the appearance of dead zones of supersaturation for growth and the difference in the effective segregation coefficient of the impurities. Analysis of the experimental results revealed that: (1) at a constant temperature, the dependence of concentration of complex species formed in saturated solutions on the concentration of different impurities can be described by an equation similar to that of the concentration dependence of density of solutions, (2) the dominant metal-containing species present in saturated solutions are negatively-charged, most stable oxalato complexes like Cu(C2O4)22−, Mn(C2O4)34−, Zn(C2O4)34−, Cr(C2O4)33− and Fe(C2O4)33−, (3) in the investigated range of impurity concentration, the solubility of Ammonium Oxalates increases linearly with the concentration of all impurities and the increase is associated with the stability of dominant complexes, (4) appearance of dead supersaturation zones in the presence of impurities is associated with instantaneous adsorption of all growth sites by dominant oxalato complexes in relatively short adsorption time, and (5) the segregation coefficient of an impurity cation M of charge z + increases with a decrease in the solubility product constant Ksp for the hydrolysis products of reactions of the type: Mz + M1(z −1)+ + H+ (where the cation M has z + charge, and H+ is hydrogen ion). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bo Zou - One of the best experts on this subject based on the ideXlab platform.

  • Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs.
    The journal of physical chemistry letters, 2015
    Co-Authors: Yuancun Qiao, Kai Wang, Hongsheng Yuan, Ke Yang, Bo Zou
    Abstract:

    Negative linear compressibility (NLC) is a relatively uncommon phenomenon and rarely studied in organic systems. Here we provide the direct evidence of the persistent NLC in organic mineral Ammonium Oxalate monohydrate under high pressure using synchrotron X-ray powder diffraction, Raman spectroscopy and density functional theory (DFT) calculation. Synchrotron X-ray powder diffraction measurement reveals that Ammonium Oxalate monohydrate shows both positive and negative linear compressibility along b-axis before 11.5 GPa. The red shift of the external Raman modes and abnormal changes of several selected internal modes in high-pressure Raman spectra further confirmed the NLC. DFT calculations demonstrate that the N—H···O hydrogen bonding “wine-rack” motifs result in the NLC along b-axis in Ammonium Oxalate monohydrate. We anticipate the high-pressure study of Ammonium Oxalate monohydrate may represent a promising strategy for accelerating the pace of exploitation and improvement of NLC materials especially...

  • negative linear compressibility in organic mineral Ammonium Oxalate monohydrate with hydrogen bonding wine rack motifs
    Journal of Physical Chemistry Letters, 2015
    Co-Authors: Yuancun Qiao, Kai Wang, Hongsheng Yuan, Ke Yang, Bo Zou
    Abstract:

    Negative linear compressibility (NLC) is a relatively uncommon phenomenon and rarely studied in organic systems. Here we provide the direct evidence of the persistent NLC in organic mineral Ammonium Oxalate monohydrate under high pressure using synchrotron X-ray powder diffraction, Raman spectroscopy and density functional theory (DFT) calculation. Synchrotron X-ray powder diffraction measurement reveals that Ammonium Oxalate monohydrate shows both positive and negative linear compressibility along b-axis before 11.5 GPa. The red shift of the external Raman modes and abnormal changes of several selected internal modes in high-pressure Raman spectra further confirmed the NLC. DFT calculations demonstrate that the N-H···O hydrogen bonding "wine-rack" motifs result in the NLC along b-axis in Ammonium Oxalate monohydrate. We anticipate the high-pressure study of Ammonium Oxalate monohydrate may represent a promising strategy for accelerating the pace of exploitation and improvement of NLC materials especially in organic systems.

Ewa Mielniczek-brzóska - One of the best experts on this subject based on the ideXlab platform.

  • Electron spin echo and spin relaxation of low-symmetry Mn2+-complexes in Ammonium Oxalate monohydrate single crystal
    Journal of magnetic resonance (San Diego Calif. : 1997), 2014
    Co-Authors: Stanisław K. Hoffmann, Stefan Lijewski, Janina Goslar, Ewa Mielniczek-brzóska
    Abstract:

    Abstract Pulse EPR experiments were performed on low concentration Mn2+ ions in Ammonium Oxalate monohydrate single crystals at X-band, in the temperature range 4.2–60 K at crystal orientation close to the D-tensor z-axis. Hyperfine lines of the resolved spin transitions were selectively excited by short nanosecond pulses. Electron spin echo signal was not observed for the low spin transition (+5/2 ↔ +3/2) suggesting a magnetic field threshold for the echo excitation. Echo appears for higher spin transitions with amplitude, which grows with magnetic field. Opposite behavior displays amplitude of echo decay modulations, which is maximal at low field and negligible for high field spin transitions. Electron spin–lattice relaxation was measured by the pulse saturation method. After the critical analysis of possible relaxation processes it was concluded that the relaxation is governed by Raman T7-process. The relaxation is the same for all spin transitions except the lowest temperatures (below 20 K) where the high field transitions (−3/2 ↔ −1/2) and (−5/2 ↔ −3/2) have a slower relaxation rate. Electron spin echo dephasing is produced by electron spectral diffusion mainly, with a small contribution from instantaneous diffusion for all spin transitions. For the highest field transition (−5/2 ↔ −3/2) an additional contribution from nuclear spectral diffusion appears with resonance type enhancement at low temperatures.

  • Solubility of Ammonium Oxalate in water-acetone mixtures and metastable zone width of their solutions
    Chemical Engineering Research and Design, 2014
    Co-Authors: Keshra Sangwal, Ewa Mielniczek-brzóska, Sylwia Barylska
    Abstract:

    Abstract Experimental results on the solubility c of Ammonium Oxalate in mixed water–acetone solvents containing acetone content x T are presented and discussed using the theory of regular solutions. It was found that: (1) the dependence of the solubility c of Ammonium Oxalate in solutions of different mixed water–acetone solvents on temperature T follows an Arrhenius-type relation, (2) the dependence of c on acetone content x at different temperature T follows the relation: ln( c  +  δ ) =  a  −  bx , where the parameters a and b are measures of deviation of a solution from ideality and the correction factor δ is related to the activity coefficient f a of the solution, which decreases with an increase in c , and (3) the dependence of the solubility c of Ammonium Oxalate in solutions of different compositions x of water–acetone mixtures is related to the dielectric constant ɛ * of the solvent mixture, following the relation ln  c  =  C  +  C 1 ɛ *, where C and C 1 are related to the parameters a and b , respectively. Study of the metastable zone width, defined as maximum undercooling Δ T max a solution saturated at a particular temperature T can withstand, of some selected solutions of mixed water–acetone solvents at different T revealed that Δ T max decreases with an increase in antisolvent content x . The results are discussed using the self-consistent Nývlt-like approach.

  • Study of the nature of Cu(II) complexes in aqueous Ammonium Oxalate solutions by ultraviolet-visible spectroscopy
    Journal of Physics: Conference Series, 2011
    Co-Authors: Ewa Mielniczek-brzóska, Keshra Sangwal
    Abstract:

    Experimental results of an investigation of aqueous Ammonium Oxalate solutions containing Cu(II) impurity by ultraviolet–visible spectroscopy are described and discussed from the standpoint of speciation of complexes. The results show that absorption of light by aqueous Ammonium Oxalate solutions containing Cu(II) impurity in the range −5 < ln(ci/c) < 2.5 of the ratio of concentrations ci and c of impurity and solute, respectively, leads to decrease or increase in the intensity of bands of the ultraviolet–visible spectral regions, and these changes may be expressed by full width at half maximum, molar extinction coefficient, peak wavelength and oscillator strength. The changes are caused by the coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex, and are related with the impurity–solute concentration ratio ci/c. The coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex in the range 0 < ln(ci/c) < 2.5 leads to the formation of Cu(C2O4) complex, but the coordination of the C2O42− ligand with Cu(C2O4) complex in the concentration ratio range −5 < ln(ci/c) < 0 results in the formation of predominantly Cu(C2O4)22− complex. The effect of successive coordination of the C2O42− ligand is well-defined in the ultraviolet spectral region but poor in the visible region.

  • The nature of Mn(II) complexes in concentrated aqueous Ammonium Oxalate solutions
    Crystal Research and Technology, 2010
    Co-Authors: Ewa Mielniczek-brzóska
    Abstract:

    The paper presents an analysis of the results of spectroscopic studies obtained in the ultraviolet range UV for unsaturated Ammonium Oxalate solutions containing Mn(II) impurity ci. The aim is to follow manganese Oxalate formation processes at different Ammonium Oxalate concentrations c and Mn(II) impurity ci and also to establish how concentrations of particular species change with a change of ratio (ci /c). Spectroscopic analysis is discussed from the standpoint of speciation of these complexes in the abovementioned solutions. The coordination of C2O42– ligand with Mn(H2O)62+ aquacomplex in the range -2 < ln(ci/c) < 1.5 leads to the formation of Mn(C2O4) and Mn(C2O4)22– complexes, but the coordination of the C2O42– ligand with Mn(C2O4)22– complex in the concentration ratio range -5 < ln(ci/c) < -2 results in the formation of predominantly Mn(C2O4)34– complex. The effect of successive coordination of the C2O42– ligand is well-defined in the ultraviolet spectral region. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  • Study of copper complexes in saturated and unsaturated aqueous Ammonium Oxalate solutions containing Cu(II) impurity
    Fluid Phase Equilibria, 2007
    Co-Authors: Keshra Sangwal, Ewa Mielniczek-brzóska
    Abstract:

    Abstract The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated Ammonium Oxalate (AO) aqueous solutions was investigated as a function of concentration c i of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of Ammonium Oxalate containing Cu(II) ions the following species are formed: Cu 2+ , Cu(OH) + , Cu(OH) 2 , CuC 2 O 4 0 and Cu(C 2 O 4 ) 2 2− in addition to C 2 O 4 2− , HC 2 O 4 − , H 2 C 2 O 4 and (NH 4 ) 2 C 2 O 4 0 species, and their concentration depends on concentrations c i of Cu(II) impurity and c of Ammonium Oxalate. The dependences of solution pH and of absorbance A and the corresponding wavelength λ for unsaturated aqueous solutions on Ammonium Oxalate concentration c containing different concentrations c i of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c . Speciation analysis revealed that Cu 2+ and CuC 2 O 4 0 , CuC 2 O 4 0 and Cu(C 2 O 4 )2 2− , and Cu(C 2 O 4 ) 2 2− complexes are predominantly present in the solute concentration intervals c ≤ 0.01  mol/dm 3 , 0.01 mol/dm 3 c 0.03  mol/dm 3 and c ≥ 0.03  mol/dm 3 , respectively. The concentration interval range 0.01 mol/dm 3 c 0.03  mol/dm 3 corresponds to the pH interval where Cu(OH) 2 is precipitated. It was found that the solubility of Ammonium Oxalate at 30  ° C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of Ammonium Oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C 2 O 4 ) 2 2− -type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC 2 O 4 0 and Cu(C 2 O 4 ) 2 2− species.

A. V. Balmasov - One of the best experts on this subject based on the ideXlab platform.

Don Ding - One of the best experts on this subject based on the ideXlab platform.

  • effect of Ammonium Oxalate strontium carbonate on the burning rate characteristics of composite propellants
    Journal of Thermal Analysis and Calorimetry, 2006
    Co-Authors: Y L Sun, Don Ding
    Abstract:

    AP/HTPB based composite propellants with additives such as Ammonium Oxalate (AO), mixture of Ammonium Oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG and FTIR experiments. The results show that the burning rates of these propellants are decreased significantly. TG-DTG experiments indicate that decomposition temperatures of AP with these additives are increased. Furthermore, the activation energy of the decomposition reaction of AP is also increased in the presence of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition of AP. The burning rates of these propellants are decreased. The burning rate temperature sensitivity of AP/HTPB based propellants is reduced significantly by the addition of AO or AO/SC. But the effect of AO is less than that of AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the same time, to reduce pressure exponent. The reduced heat release at the burning surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity. Synergetic action is probably produced between AO and SC within AP/HTPB based propellants in the pressure range tested. This synergetic effect causes the heat release to reduce and the burning surface temperature to increase. Moreover, it makes the net exothermal reaction of condensed phase become little dependent on T0. Thus, the burning rate temperature sensitivity is reduced.

  • Effect of Ammonium Oxalate/strontium carbonate on the burning rate characteristics of composite propellants
    Journal of Thermal Analysis and Calorimetry, 2006
    Co-Authors: Y L Sun, Don Ding
    Abstract:

    AP/HTPB based composite propellants with additives such as Ammonium Oxalate (AO), mixture of Ammonium Oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG and FTIR experiments. The results show that the burning rates of these propellants are decreased significantly. TG-DTG experiments indicate that decomposition temperatures of AP with these additives are increased. Furthermore, the activation energy of the decomposition reaction of AP is also increased in the presence of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition of AP. The burning rates of these propellants are decreased. The burning rate temperature sensitivity of AP/HTPB based propellants is reduced significantly by the addition of AO or AO/SC. But the effect of AO is less than that of AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the same time, to reduce pressure exponent. The reduced heat release at the burning surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity. Synergetic action is probably produced between AO and SC within AP/HTPB based propellants in the pressure range tested. This synergetic effect causes the heat release to reduce and the burning surface temperature to increase. Moreover, it makes the net exothermal reaction of condensed phase become little dependent on T0. Thus, the burning rate temperature sensitivity is reduced.