Characterisation of the Six-coordinated Octahedral Site in Cd(C4H2O4) · 2H2O Crystals

Optical absorption spectra of Co(II) and Ni(II) doped cadmium maleate dihydrate (CMDH) are recorded at room temperature and liquid nitrogen temperature. The UV–VIS–NIR spectra are characteristic of the transition metal ions in solids. The results and analyses of the spectra indicate near octahedral site symmetry for cobalt ion and trigonally distorted octahedral site symmetry for nickel ion. The following crystal field parameters are derived. The IR spectra are characteristic of the host lattice CMDH.     

X-Ray diffraction and IR-spectroscopic studies of UO2(n-C3H7COO)2(H2O)2 and Mg(H2O)6[UO2(n-C3H7COO)3]2

Single crystals of UO₂(n-C₃H₇COO)₂(H₂O)₂ (I) and Mg(H₂O)₆[UO₂(n-C₃H₇COO)₃]₂ (II) are synthesized. Their IR-spectroscopic and X-ray diffraction studies are performed. Crystals I are monoclinic, a = 9.8124(7) Å, b = 19.2394(14) Å, c = 12.9251(11) Å, β = 122.423(1)°, space group P2₁/c, Z = 6, and R = 0.0268. Crystals II are cubic, a = 15.6935(6) Å, space group $Pa\bar 3$ , Z = 4, and R = 0.0173. The main structural units of I and II are [UO₂(C₃H₇COO)₂(H₂O)₂] molecules and [UO₂(C₃H₇COO)₃]^? anionic complexes, respectively, which belong to AB ₂ ⁰¹ M ₂ ¹ (I) and AB ₃ ⁰¹ (II) crystal chemical groups of uranyl complexes (A = UO ₂ ²⁺ , B ⁰¹ = C₃H₇COO^?, and M ¹ = H₂O). A crystal chemical analysis of UO₂ L ₂ · nH₂O compounds, where L is a carboxylate ion, is performed.     

On the (MgxNi1–x)SeO4 · 6 H2O and (MgxCu1–x)SeO4 · 5 H2O mixed crystal formation

Mixed crystals (Mg_xNi_1–x)SeO₄ · 6 H₂O and (Mg_xCu_1–x)SeO₄ · 5 H₂O have been prepared studying the solubility in the MgSeO₄–NiSeO₄–H₂O and MgSeO₄–CuSeO₄–H_2O systems at 25 °C. It has been shown that the monoclinic structure of MgSeO₄ · 6 H₂O is unstable and undergoes a change into tetragonal structure due to the included nickel ions (about 4 at %). The lattice parameters of (Mg_{xNi 1–x})SeO₄ 6 H₂O have been calculated. It has been established that the magnesium ions incorporate isodimorphously in the crystal structure of CuSeO₄ · 5 H₂O which could be an indication of the existence of MgSeO₄ · 5 H₂O isostructural with the triclinic CuSeO₄ 5 H₂O. The distribution coefficients of the salt components between the liquid and solid phases have been calculated.     

Crystal Structure Determination of Nickel (2,2-Dipyridyl) Sulphate Hexahydrate [Ni(C10H8N2) · 4 H2O]SO4 · 2H2O

[Ni(C₁₀H₈N₂) · 4 H₂O]SO₄ · 2 H₂O, Mr = 418.7, monoclinic, P1 , a = 7.781(3), b = 9.421(3), c = 11.457(4) Å, α = 87.54(2)º, β = 96.40(2)º, γ = 102.58(2)º, ν = 814.5 Å, D_x = 1.26 g/cm³, Z = 2, (MoKx) = 0.71073 Å, μ = 7.0 cm⁻¹: T = 23 °C, R = 0.047 for 2139 reflections having intensities greater than 36. The structure was solved using the Patterson heavy-atom method and the remaining atoms were located in succeeding difference Fourier syntheses. The structure was then refined by full matrix least-squares using anisotropic temperature factors. Hydrogen atoms were located and their positions and isotropic parameters were refined.     

Electronic Structure of [Cu(C7H4NO3S)2(H2O)4] · 2H2O Crystal

The electronic absorption spectrum and ESR spectrum of the crystal of the title compound [Cu(C₇H₄NO₃S)₂(H₂O)₄] · 2 H₂O, are measured. The experimental results are discussed quantitatively by using the ligand field theory and the radial wave function of non-free Cu(II). The electronic structure of the compound is in agreement with its crystal structure.     

Growth and Physical Characterization of Double Cation Hydrogen Double Sulphate System Li2NaH(SO4)2 · H2O

Single crystals of Li₂NaH(SO₄)₂ H₂O are grown from aqueous solution, containing equimolar amounts of Li₂SO₄ H₂O and NaHSO₄ from 80°C down to 30°C over a period of 15 days, resulting in large good quality crystals. The as-grown crystals are verified by using XRD powder technique. The local structure is discussed in the light of vibrational spectroscopy. Water of crystallization is evidenced from both IR and Raman spectra. Several endothermic and an exothermic phase transition anomalies have been observed from DTA scan. Considerable weight loss is observed at 108°C from thermogravimetric study (TGA). The melting point of the material is found to be 450 °C. The density of the compound is measured to be 2.5217 g/cm³.     

Electrical Conductivity and Thermal Dehydration Studies of Mixed Single Crystals of BaCu(C2O4)2 · 6 H2O,Ba1–xCuxC2O4 · 4 H2O and Ba1–2x(NH4)2xC2O4 · 4 H2O

The measurement of electrical conductivity for the investigation of the number of water molecules present in the mixed crystals of barium copper oxalate and barium ammonium oxalate lattice have been carried out in the temperature range 30 to 450 °C. The dehydration temperature and the number of water molecules removed out of the structure at a particular temperature is estimated from the sharp increase in conductivity at these points. The almost steep increase of conductivity is attributed to the increase in the number of mobile charge carriers H⁺ and OH^– ions generated from the escaping water molecules. The study of electrical conductivity in association with the thermal behaviour has been used to understand the mechanism of conduction.     

Der Einfluß von Zusätzen auf die Verschiebungsgeschwindigkeit von KCl-{100}-Flächen (K4[Fe(CN)6] · 3 H2O,PbCl2, CoCl2 · 6 H2O,CuCl2 · 2H2O)

The influence of inorganic additives (K₄[Fe(CN)₆] · 3 H₂O, PbCl₂, CoCl₂ · 6 H₂O, CuCl₂ · 2H₂O) on the displacement velocity (VG) of KCl-{100}-faces has been investigated. These additives lower the VG according to the formula given by Bliznakov. The effect of lowering diminishes in the order K₄[Fe(CN)₆] · 3 H₂O, PbCl₂, CoCl₂ · 6 H₂O and CuCl₂ · 2H₂O. In the very same sequence the structure affinity to KCl decreases. An explanation for the different effectivities of CoCl₂ · 6 H₂O and CuCl₂ · 2 H₂O mentioned above is given in the heat of adsorption on {100}-faces of KCl. It was estimated to be 7.1 ± 1 kcal for CoCl₂ · 6 H₂O and 5,5 ± 1,2 kcal for CuCl₂ · 2 H₂O. At a high supersaturation of KCl (1,5) and in the presence of CuCl₂ · H₂O VG of KC1-{100}-faces increases within a certain interval of concentration.     

Synthesis and X-ray structure studies of complex [Cu(o-phenanthroline)2 (saccharin)] · (saccharin) · 2 H2O

The title compound has been synthesized and its crystal structure determined at room temperature, M_r = 824.34, triclinic, space group P–1(2), a = 13.622(4), b = 13.770(4), c = 11.167(3) Å; α = 104.83(2), β = 110.01(2), γ = 62.04(2) degree; U = 1727.0(9) ų, Z = 2, D_calc = 1.59 g/cm³. The final R is 0.066 for 3299 independent observed reflections with I ≧ 3σ(I). The crystal structure consists of repeated [Cu(o-phen)₂(sac)]⁺ cations, non-coordinated saccharin anion and two lattice water. And the central ion Cu²⁺ forms a trigonal-bipyramidal stereochemistry.     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.     

The Thermal Decomposition of Polyhalite K2SO4 · MgSO4 · 2 CaSO4 · 2 H2O

The thermal decomposition of polyhalite (K₂SO₄ · MgSO₄ · 2 CaSO₄ · 2H₂O) was investigated by DSC/TG and X-ray powder diffraction. The decomposition of the polyhalite starts at 285 °C in releasing the crystal water within one step. Simultaneously the decomposition of the polyhalite into anhydrite and two solid solutions of the compositions K₂SO₄ · 1.76 MgSO₄ · 0.24 CaSO₄ and K₂SO₄ · 0.64 MgSO₄ · 1.36 CaSO₄ is taking place. The mechanism of decomposition runs through K₂SO₄ · MgSO₄ CaSO₄. This phase reacts immediately to the solid solutions, mentioned above.     

Synthesis and characterization of Ce2(SO4)3 · 5(H,D)2 O

The synthesis of cerium sulphate pentahydrate and its structure investigated by X-ray diffraction methods are reported. Analysis of the precession and Weissenberg photographs show that the crystals are twinned perfectly, in the sense that they are made of two single crystals with the true space group Cc. The dehydration of this compound has been studied using thermogravimetry and differential scanning calorimetric analysis in the temperature range 360 to 650 K. Powder Raman spectra of Ce₂(SO₄)₃ · 5 H₂O and Ce₂(SO₄)₃ · 5 D₂O have been measured at room temperature and the spectral assignments have been carried out by comparing these spectra with each other. Evidence of intermolecular hydrogen bonding has been found.     

Crystal growth and physical properties of monoclinic L-arginine hydrochloride monohydrate,C6H14O2N4HCl · H2O,and L-arginine hydrobromide monohydrate,C6H14O2N4HBr · H2O

Single crystals of optical quality of L-arginine HCl · H₂O and L-arginine HBr · H₂O with dimensions up to 80 × 60 × 30 mm have been grown from aqueous solutions by controlled evaporation at about 310 K. The isotypic crystals exhibit a quite similar behaviour with respect to morphological, pyroelectric, dielectric, optical, thermal expansion, electrostrictive, electrooptic, elastic, thermoelastic and non-linear optical properties. A distinct anisotropy of the longitudinal elastic stiffness is observed with a maximum along the direction of the alignment of the arginine ions. Nearly in the same direction a minimum of thermal expansion, dielectric constant and index of refraction is found. The pyroelectric, electrostrictive, electrooptic and non-linear-optical effects are of only mediocre magnitude except the electrostrictive constant d₂₁₁ which surmounts the longitudinal electrostrictive constant d₁₁₁ of alpha-quartz by a factor three.     

Crystal structure of Zn[Cl2Ti(C5H5)2]2·2C6H6

The structure of crystals of the composition Zn[Cl₂Ti(C₅H₅)₂]₂·2C₆H₆ has been determined from Patterson and Fourier syntheses of two projections, and refined toR = 0·117 by full-matrix three-dimensional least-squares methods. The crystals are orthorhombic:Pbcn,a = 18·45(5),b = 15·40(6),c = 11·35(3) Å,Z= 4. The complex consists of a central distorted ZnCl ₄ ^2– tetrahedron linked along the Cl—Cl edges to two distorted TiCl₂(C₅H₅)₂ ⁺ tetrahedra in such a way that their centres are nearly collinear The two C₆H₆ molecules in the formulae unit may be regarded as benzene of crystallization.     

Structure of monoclinic acridine orange hydrochloride monohydrate,C17H19N3 · HCl · H2O

M_r = 319.82, monoclinic P2₁/a, Z = 4, a = 14.545(5), b = 15.562(6), c = 8.538(4) Å, β = 120.66(3)°, V = 1662(1) ų, D_m = 1.27 Mgm⁻³, D_x = 1.278 Mgm⁻³, λ(MoKα) = 0.71069 Å, μ(MoKα) = 0.24 mm⁻¹, T = 297 K. Final R = 0.049 for 1485 observed reflections. All hydrogen atoms were located and refined isotropically. Bond lengths (σ = 0.004 Å) and angles (σ = 0.3°) are normal. The substance is a derivative of acridine. The structure consists of chloride anions, bisdimethylaminoacridinium cations and water molecules. In the solid state the molecules are approximately planar. Pairs of cations form dimers with parallel planes connected by an I inversion centre and plane distances of 3.474 Å. They overlap with partial areas of all three six membered rings.     

Nucleation of struvite (MgNH4PO4 · 6 H2O) single crystals and aggregates

The conditions (concentration and pH) for preparation of single crystals of struvite at 25 °C from ammoniacal solutions equimolar with respect to magnesium and phosphate ions are given. The limits are found above which crystal aggregates (twins or dendrites) precipitate as dominant morphology. The mechanisms of nucleation are discussed and the interfacial tension between crystals and solution is evaluated.