scholarly journals The Influence of Aqueous Se(IV) on the Stability of Different CaCO3 Polymorphs Precipitated under Ambient Conditions

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1238
Author(s):  
Angeles Fernandez-Gonzalez ◽  
Alba Lozano-Letellier ◽  
Begoña Fernandez
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Aging Process ◽  
Experimental Studies ◽  
Atomic Ratio ◽  
Ambient Conditions ◽  
Calcium Carbonates ◽  
Cell Parameters ◽  
The Stability

Selenium is an essential bio-element, but because of its bioaccumulation potential, it can become toxic and is an important pollutant. The ubiquitous mineral calcite (CaCO3) has the ability to immobilize anions as SeO32− by different sorption or coprecipitation processes. Experimental studies have found that SeO32− can incorporate in the crystal structure of calcite by substituting CO32−. The presence of foreign ions in aqueous solution strongly affects CaCO3 precipitation, helping stabilize less stable polymorphs such as vaterite and aragonite or hydrated phases. In this work, we studied the aging process of calcium carbonates precipitated from aqueous solutions highly supersaturated with respect to CaCO3 and slightly supersaturated with respect to CaSeO3·H2O under ambient conditions, for times up to 30 days in which solids were kept in the remaining aqueous solution. Under these conditions, CaCO3 precipitated mainly as low crystallinity vaterite aggregates that hosted up to 16% atomic ratio Se:C. Vaterite purified and increased its crystallinity with aging time, but the vaterite–calcite transformation was strongly inhibited. The incorporation of Se(IV) in vaterite did not significantly affect the cell parameters or the external morphology of the aggregates. The precipitation of selenite as CaSeO3·H2O was conditioned by the availability of free Ca2+ and SeO32− that was not previously incorporated into precipitated carbonates.

Synthesis, single-crystal structure determination and Raman spectra of the tricyanomelaminates NaA5[C6N9]2 · 4 H2O (A = Rb, Cs)

2016 ◽  
Vol 71 (4) ◽  
pp. 327-332 ◽  
Author(s):  
Olaf Reckeweg ◽  
Armin Schulz ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Single Crystal ◽  
Raman Spectra ◽  
Structure Determination ◽  
Single Crystal Structure ◽  
Crystal Structure Determination ◽  
Ambient Conditions ◽  
Space Group ◽  
Cell Parameters

AbstractTransparent colorless crystals of NaA5[C6N9]2 · 4 H2O (A = Rb, Cs) were obtained by blending aqueous solutions of Na3[C6N9] and RbF or CsF, respectively, and subsequent evaporation of the water under ambient conditions. Both compounds crystallize in the space group P21/m (no. 11) with the cell parameters a = 815.56(16), b = 1637.7(4) and c = 1036.4(3) pm, and β = 110.738(12)° for NaRb5[C6N9]2 · 4 H2O and a = 843.32(6), b = 1708.47(11) and c = 1052.42(7) pm, and β = 112.034(2)° for NaCs5[C6N9]2 · 4 H2O, respectively. Raman spectra of the title compounds complement our results.

Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems: synthesis and crystal structures of Rb2[(UO2)(Cr2O7)(NO3)2] and two new polymorphs of Rb2Cr3O10

2021 ◽  
Vol 236 (1-2) ◽  
pp. 11-21
Author(s):  
Evgeny V. Nazarchuk ◽  
Oleg I. Siidra ◽  
Dmitry O. Charkin ◽  
Stepan N. Kalmykov ◽  
Elena L. Kotova
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Crystal Structures ◽  
Hydrothermal Treatment ◽  
Ambient Conditions ◽  
Screw Axis ◽  
3D Framework ◽  
Solution Acidity

Abstract Three new rubidium polychromates, Rb2[(UO2)(Cr2O7)(NO3)2] (1), γ-Rb2Cr3O10 (2) and δ-Rb2Cr3O10 (3) were prepared by combination of hydrothermal treatment at 220 °C and evaporation of aqueous solutions under ambient conditions. Compound 1 is monoclinic, P 2 1 / c $P{2}_{1}/c$ , a = 13.6542(19), b = 19.698(3), c = 11.6984(17) Å, β = 114.326(2)°, V = 2867.0(7) Å3, R 1 = 0.040; 2 is hexagonal, P 6 3 / m $P{6}_{3}/m$ , a = 11.991(2), c = 12.828(3) Å, γ = 120°, V = 1597.3(5) Å3, R 1 = 0.031; 3 is monoclinic, P 2 1 / n $P{2}_{1}/n$ , a = 7.446(3), b = 18.194(6), c = 7.848(3) Å, β = 99.953(9)°, V = 1047.3(7) Å3, R 1 = 0.037. In the crystal structure of 1, UO8 bipyramids and NO3 groups share edges to form [(UO2)(NO3)2] species which share common corners with dichromate Cr2O7 groups producing novel type of uranyl dichromate chains [(UO2)(Cr2O7)(NO3)2]2−. In the structures of new Rb2Cr3O10 polymorphs, CrO4 tetrahedra share vertices to form Cr3O10 2− species. The trichromate groups are aligned along the 63 screw axis forming channels running in the ab plane in the structure of 2. The Rb cations reside between the channels and in their centers completing the structure. The trichromate anions are linked by the Rb+ cations into a 3D framework in the structure of 3. Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems is discussed.

Addition of Aliphatic and Aromatic Amines to Catechol in Aqueous Solution Under Oxidizing Conditions

1989 ◽  
Vol 42 (3) ◽  
pp. 365 ◽  
Author(s):  
MK Manthey ◽  
SG Pyne ◽  
RJW Truscott
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Aromatic Amines ◽  
Aliphatic Amines ◽  
Substitution Pattern ◽  
Vinylogous Amides ◽  
The Stability

The oxidation of catechol in the presence of two aliphatic and aromatic amines has been investigated. In aqueous solutions of pH 7.0 and 11.7, the substitution pattern of the adduct was dependent on the type of amine used. Aromatic amines produced 4,5-disubstituted o-quinones, whereas aliphatic amines gave either 2,4,5-trisubstituted or 2,4-disubstituted o-quinone adducts. A rationale based upon the stability of vinylogous amides is presented to account for the observed substitution pattern.

Determination of the Crystal Structure and Redefinition of Tsugaruite, Pb28As15S50Cl, the First Lead-Arsenic Chloro-Sulfosalt

2020 ◽  
Author(s):  
Cristian Biagioni ◽  
Luca Bindi ◽  
Koichi Momma ◽  
Ritsuro Miyawaki ◽  
Yoshitaka Matsushita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Specific Position ◽  
Actual Classification ◽  
Aomori Prefecture

Abstract Tsugaruite was originally defined as a lead-arsenic sulfosalt from the Yunosawa mine, Aomori Prefecture, Japan. Until recently its crystal structure remained unsolved and its actual classification in the sulfosalt realm was unknown. Here the refinement of the crystal structure of tsugaruite using single-crystal X-ray diffraction data is reported. The mineral is orthorhombic, space group P2nn, with unit-cell parameters a = 8.0774(10), b = 15.1772(16), c = 38.129(4) Å, V = 4674.3(9) Å3, in agreement with previous studies. The solution of the crystal structure of this mineral revealed Cl occupying a specific position. Chlorine was thus sought and found using the electron microprobe; the average of six spot analyses gave (in wt.%): Pb 68.04, As 12.83, S 18.29, Cl 0.63, total 99.80. The empirical formula, calculated on the basis of Pb + As = 43 atoms per formula unit, is Pb28.26As14.74S49.08Cl1.52. Tsugaruite is an N = 4 plesiotypic derivative of the homologous series of Pb-Sb chloro-sulfosalts having the general formula Pb(2+2N)(Sb,Pb)(2+2N)S(2+2N)(S,Cl)(4+2N)ClN. It has a Cl/(Cl + S) atomic ratio close to that of other known Pb-Sb chloro-sulfosalts (pillaite, pellouxite) and slightly higher than that of dadsonite.

Microporous crystal structure of labuntsovite-Fe and high-pressure behavior up to 23 GPa

2018 ◽  
Vol 74 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Sergey M. Aksenov ◽  
Elena A. Bykova ◽  
Ramiza K. Rastsvetaeva ◽  
Nikita V. Chukanov ◽  
Irina P. Makarova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystal ◽  
Cross Section ◽  
Structure Refinement ◽  
Alkaline Complex ◽  
X Ray ◽  
Cell Parameters ◽  
Diamond Anvil ◽  
The Stability

Labuntsovite-Fe, an Fe-dominant member of the labuntsovite subgroup, was first discovered in the Khibiny alkaline massif on Mt Kukisvumchorr [Khomyakov et al. (2001). Zap. Vseross. Mineral. Oba, 130, 36–45]. However, no data are published about the crystal structure of this mineral. Labuntsovite-Fe from a peralkaline pegmatite located on Mt Nyorkpakhk, in the Khibiny alkaline complex, Kola Peninsula, Russia, has been investigated by means of electron microprobe analyses, single-crystal X-ray structure refinement, and IR and Raman spectroscopies. Monoclinic unit-cell parameters of labuntsovite-Fe are: a = 14.2584 (4), b = 13.7541 (6), c = 7.7770 (2) Å, β = 116.893 (3)°; V = 1360.22 (9) Å3; space group C2/m. The structure was refined to final R 1 = 0.0467, wR 2 = 0.0715 for 3202 reflections [I > 3σ(I)]. The refined crystal chemical formula is (Z = 2): Na2K2Ba0.7[(Fe0.5Ti0.1Mg0.05)(H2O)1.3]{[Ti2(Ti1.9Nb0.1)(O,OH)4][Si4O12]2}·4H2O. The high-pressure in situ single-crystal X-ray diffraction study of the labuntsovite-Fe has been carried out in a diamond anvil cell. The labuntsovite-type structure is stable up to 23 GPa and phase transitions are not observed. Calculations using the BM3 equation of state resulted in the bulk modulus K = 72 (2) GPa, K′0 = 3.7 (2) and V 0 = 1363 (2) Å3. Compressing of the heteropolyhedral zeolite-like framework leads to the deformation of main structural units. Octahedral rods show the gradual increase of distortion and the wave-like character of rods becomes more distinct. Rod deformations result in the distortion of the silicon–oxygen ring which is not equal in different directions. Structural channels are characterized by a different ellipticity–pressure relationship: the cross-section of the largest channel I and channel II demonstrates the stability of the geometrical characteristics which practically do not depend on pressure: ∊channel I ≃ 0.85 (4) (cross-section is rather regular) and ∊channel II ≃ 0.52 (2) within the whole pressure range. However, channel III is characterized by the increasing of ellipticity with pressure (∊ = 0.40 → 0.10).

Synthesis, single-crystal structure determination and Raman spectrum of Cu[C(CN)3]2·2 NH3

2015 ◽  
Vol 70 (3) ◽  
pp. 177-181
Author(s):  
Olaf Reckeweg ◽  
Armin Schulz ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Single Crystals ◽  
Structure Determination ◽  
Aqueous Ammonia ◽  
Ambient Conditions ◽  
Light Blue ◽  
Cell Parameters ◽  
First Time

AbstractTransparent, light blue crystals of Cu[C(CN)3]2·2 NH3 were obtained by dissolving Cu[C(CN)3]2 in aqueous ammonia and subsequent evaporation of the solvent under ambient conditions. Cu[C(CN)3]2·2 NH3 crystallizes in the space group C2/c (no. 15, Z = 4) with the cell parameters a = 1291.9(3), b = 753.18(15) and c = 1200.8(2) pm, and β = 92.68(3)°. The nature of the tricyanomethanide anion and the ammonia molecules were verified by Raman spectroscopy. Single crystals of Ag[C(CN)3] and Cu[C(CN)3]2 were synthesized, the known structures were confirmed and their Raman spectra were recorded for the first time for comparison.

STUDIES ON DICYANOTRIAZOLE: I. THE CONDUCTANCE OF DILUTE AQUEOUS SOLUTIONS OF DICYANOTRIAZOLE AT 25 °C.

1942 ◽  
Vol 20b (8) ◽  
pp. 161-167 ◽  
Author(s):  
E. G. Taylor
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Dissociation Constant ◽  
Experimental Studies ◽  
Equivalent Conductance ◽  
A Value ◽  
Dilute Aqueous Solution ◽  
Dilute Aqueous Solutions

Previous experimental studies of dicyanotriazole have resulted in statements that the compound is an acid comparable in strength with the strong mineral acids.In the present work, measurements of the equivalent conductance of dicyanotriazole in dilute aqueous solution give the dissociation constant of the acid as 3.378 × 10−2 at 25 °C., thus showing it to be an acid possessing about the same strength as dichloracetic acid.The limiting equivalent conductance of dicyanotriazole at 25 °C. is 384.9. The earlier work gave a value of 397.44.

scholarly journals Polymorph evolution during crystal growth studied by 3D electron diffraction

IUCrJ ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 5-9 ◽  
Author(s):  
Edward T. Broadhurst ◽  
Hongyi Xu ◽  
Max T. B. Clabbers ◽  
Molly Lightowler ◽  
Fabio Nudelman ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Electron Diffraction ◽  
Electron Diffraction Data ◽  
Ambient Conditions ◽  
Prolonged Standing ◽  
Continuous Rotation ◽  
Stability Order ◽  
3D Electron ◽  
The Stability ◽  
Stable Polymorph

3D electron diffraction (3DED) has been used to follow polymorph evolution in the crystallization of glycine from aqueous solution. The three polymorphs of glycine which exist under ambient conditions follow the stability order β < α < γ. The least stable β polymorph forms within the first 3 min, but this begins to yield the α-form after only 1 min more. Both structures could be determined from continuous rotation electron diffraction data collected in less than 20 s on crystals of thickness ∼100 nm. Even though the γ-form is thermodynamically the most stable polymorph, kinetics favour the α-form, which dominates after prolonged standing. In the same sample, some β and one crystallite of the γ polymorph were also observed.

scholarly journals Synthesis, crystal structure and physical properties of the TbCo4.5SixLi0.5-x solid solution

2021 ◽  
Vol 22 (3) ◽  
pp. 577-584
Author(s):  
I. Stetskiv ◽  
V. Kordan ◽  
I. Tarasiuk ◽  
V. Pavlyuk
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Electrode Materials ◽  
Rietveld Method ◽  
Structure Type ◽  
Experimental Conditions ◽  
X Ray ◽  
Cell Parameters ◽  
Arc Melting ◽  
The Stability

Alloys from the region of existence of the solid solution TbCo4.5SixLi0.5-x were synthesized by arc melting. Quantitative and qualitative composition of alloys and powders of electrode materials was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The Tb/Co/Si ratio in the samples was confirmed by X-ray fluorescence spectroscopy. The change in cell parameters within the solid solution existence was established by the results of X-ray powder diffraction (TbCo4.5SixLi0.5-x, x = 0.1–0.4: a = 4.9518(5) – 4.9324(3), c = 3.9727(4) – 3.9746(3) Å). The crystal structure of the solid solution was determined by the Rietveld method (CaCu5 structure type, space group P6/mmm). Cobalt atoms are partially replaced by silicon and lithium only in 2c position. The ability of alloys to reversibly absorb hydrogen was studied by the method of electrochemical hydrogenation. Under experimental conditions the amount of deintercalated hydrogen was about 0.19 H/f.u. The change in cell parameters after hydrogenation (volume increases from 83.74(1) to 85.54(6) Å3) and the stability of the electrode in the electrolyte solution was further confirmed by X-ray phase analysis. Measurements of the electrical resistivity of the samples indicated a decrease of resistivity value with a slight increase in the amount of alkali metal in samples.

scholarly journals Lead–Antimony Sulfosalts from Tuscany (Italy). XXIV. Crystal Structure of Thallium-Bearing Chovanite, TlPb26(Sb,As)31S72O, from the Monte Arsiccio Mine, Apuan Alps

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 535 ◽  
Author(s):  
Cristian Biagioni ◽  
Yves Moëlo ◽  
Natale Perchiazzi ◽  
Nicola Demitri ◽  
Giovanni Lepore
Keyword(s):  
Crystal Structure ◽  
Atomic Ratio ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Cell Parameters ◽  
Quartz Veins ◽  
A New Species ◽  
Apuan Alps ◽  
The Ideal

A thallium-bearing variety of the lead–antimony oxysulfosalt chovanite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy) has been reexamined. It occurs as thin, ribbon-like crystals, black in color, up to 5 mm in length in vugs of dolomite ± baryte ± quartz veins embedded in the metadolostone of the Sant’Olga level. Associated minerals are rouxelite, robinsonite, sphalerite, valentinite, baryte, dolomite, quartz, and Ba-rich K-feldspar. Chemical analysis pointed to contents of Tl up to 0.86 apfu, corresponding to the ideal chemical formula TlPb26(Sb,As)31S72O. The structural role of thallium has been investigated using single-crystal X-ray diffraction using synchrotron radiation (λ = 0.59040 Å). Thallium-rich chovanite is monoclinic, space group P21/c, with unit-cell parameters a = 34.280(3), b = 8.2430(7), c = 48.457(4) Å, β = 106.290(4)°, and V = 13143(2) Å3. The crystal structure was refined to a final R1 = 0.083 for 12,052 reflections with Fo > 4σ(Fo) and 1210 refined parameters. The general features of thallium-rich chovanite agree with those of chovanite. Thallium is present as Tl+; it is disordered among two mixed (Pb/Tl) positions, with a Tl/Pb atomic ratio below 1, that precludes this compound to be a new species.

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