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.     

On the crystal structure type of 2 CsCl · CoCl2 · 2 H2O

The following three-component systems have been studied: CsCl MnCl₂ H₂O at 25 °C; 2 CsCl · CuCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 10 °C and 2 CsCl · MnCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 25 °C and 10 °C. It was established that Co²⁺-ions do not substitute isodimorphously the Cu²⁺-ions in the tetragonal salt 2 CsCl · CuCl₂ · 2 H₂O, whereas in the case of the triclinic salt 2 CsCl · MnCl₂ · 2 H₂O they can substitute isodimorphously the Mn²⁺-ions. The theoretical considerations supported by the results obtained allow to predict the existence of the double salt 2 CsCl · CoCl₂ · 2 H₂O as well as the type of its crystal structure — triclinic, space group P1 .     

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.     

EPR spectra of irradiated Na2Cr2O7 · 2 H2O crystals

The EPR spectra of X-irradiated Na₂Cr₂O₇ · 2 H₂O crystals grown from the aqueous solution at room temperature are studied. Three groups of lines are detected, which marked conventionally as C₁, C₂ and C₃. Each of the C₁ and C₂ line groups is a superposition of two doublets. The lines are interpreted as due to the Cr⁵⁺ ions in the distorted (stretched) oxygenous tetrahedron. The doublet structure is due to hyperfine interaction with nuclei of 1/2 spin which are protons of water. It is shown that the C₁ and C₂ line groups are due to the centers of the same type with different orientations in the lattice. The principal g-tensor values for these centres were as follows: g_z = 1.916, g_y = 1.978, g_x = 1.986.     

Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O

The crystal chemistry of the double salts Me⁺Cl · Me²⁺Cl₂ · 2 H₂O (where (Me⁺ = K, Rb, Cs; Me²⁺ = Mn, Fe, Co, Ni) is considered. It is concluded that these salts crystallize in three types of structures, the Me⁺ ion size being decisive for the structure type. Salts containing the large Cs⁺ ions crystallize in an orthorhombic structure in which [Me²⁺ (H₂O)₂Cl₄] octahedra form chains having common Cl⁻ corners. Salts with the smaller K⁺ ions crystallize in a tricline system, the [Me²⁺ (H₂O)₂Cl₄] octahedra being connected by a common Cl–Cl edge and forming dimers. When the intermediate in size Rb⁺ ions are present in the salts, either of the above structures is possible as well as a monoclinic structure which is intermediate in symmetry. The expected isostructure of the cesium salts was checked by studing the CsCl · NiCl₂ · 2 H₂O–CsCl · MnCl₂ · 2H₂O–H₂O system. A continuous series of mixed crystals is found.     

Thermal expansion,pyroelectricity and linear optical properties of Li2SeO4·H2O and Li2SO4·H2O

Large single crystals of polar Li₂SeO₄·H₂O were grown at 343 K from aqueous solution. Temperature dependent thermal expansion coefficients of Li₂SeO₄·H₂O and Li₂SO₄·H₂O were determined within the temperature range 133 K–313 K and coefficients of the pyroelectric effect within the temperature range 183–343 K. Refractive indices between 365 nm and 1530 nm as well as unpolarized absorption spectra of Li₂SeO₄·H₂O and Li₂SO₄·H₂O were measured and phase‐matching curves for second harmonic generation were calculated. Both compounds allow type I and type II phase‐matching at wavelengths from about 650 nm to the near infrared region. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

Structural features of a new [Fe(nicotinamide)2(H2O)4]·[Fe(H2O)6]·(SO4)2·2H2O complex

A new nicotinamide complex of Fe(II) cation was prepared by reaction between ferrous sulfate and nicotinamide in aqueous solution. The complex was characterized on the basis of elemental analysis, FT IR and UV–VIS spectroscopy, electrochemistry (cyclic voltammetry) and X–ray crystallography. The complex consists of the molecular composition of [Fe(nicotinamide)₂(H₂O)₄]· [Fe(H₂O)₆]·(SO₄)₂·2H₂O. The complex crystallizes in the monoclinic space group P 2₁/c [a = 12.862(3), b = 7.110(3), c = 16.382(3) Å; β = 95.79(2)°]. It has been proven that nicotinamide is coordinated to Fe(II) through the nitrogen atom of its heterocyclic ring. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Synthesis of radial‐like ZnO structure by hydrothermal method with ZnSO4·7H2O and Zn(CH3COO)2·2H2O as zinc sources

Radial‐like ZnO structures were prepared using zinc sulfate (ZnSO₄·7H₂O) and zinc acetate [Zn(CH₃COO)₂·2H₂O] as zinc sources by a facile template‐free hydrothermal method in this paper. Structural and optical properties of radial‐like ZnO structures are characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV‐vis spectrophotometer and photoluminescence measurement (PL). It has been found that the distinct surface morphologies of radial‐like ZnO structures grown by different zinc sources. Slim radial‐like ZnO with a hexagonal wurtzite structure is grown by using ZnSO₄·7H₂O as zinc sources, whereas coarse radial‐like ZnO with zincite structure is achieved by zinc acetate. The UV‐vis absorption spectra of them both display an obvious and significant absorption in the ultraviolet region. The room temperature PL spectra of ZnO structures grown by two different zinc sources possess a common feature that consists of a strong ultraviolet (UV) peak and visible emission band.     

Crystal Structure Study of Co(II) Complexes with 2,2′-(1,4-Ethylenedioxyl) Dibenzoic Acid-[Co · L · (H2O)3]n · nH2O· 0.2 nH2O

The structure ofS the title complex [Co. L. (H₂O)₃]_n. nH₂O. 0.2 nH₂O has been established by single crystal X-ray diffraction. Crystals of the complex are monoclinic, space group C2/c with cell constants α = 45.29(4), b=10.631(6), c = 8.015(6) Å, β = 90.65(8)°, Z = 8, D_c = 1.489 g. cm⁻³ The structure was solved and refined to R =0.0478 (wR = 0.0577). In the chain structure, Co(II) ions are hexacoordinated by 0 atoms in an octahedral arrangement. CoO₆ octahedra share corners (bridged) through O atoms of water, with each L^2--ligand binding two adjacent Co atoms.     

Ferroelectric and ferroelastic properties of Rb2MnCl4·2H2O

Rb₂MnCl₄·2H₂O crystal belonging to the family of tetrahalogeno‐metallates dihydrates has been subjected to thermal, optical and dielectric studies. At room temperature the optical study under a polarization microscope has revealed a ferroelastic domain structure. At 240 K a dielectric anomaly, characteristic of the week ferroelectric phase transition, has been also observed. Moreover, below the temperatures of the phase transitions dielectric dispersion has appeared. Ferroic properties of Rb₂MnCl₄·2H₂O crystal have been compared to those of other tetrachlorides dehydrates. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystallization kinetics of MgSO4 · 7 H2O in presence of tenside

The effect of sodium dodecyl sulfate (SDS) on crystallization kinetics and crystal habit of MgSO₄ · 7 H₂O from aqueous solutions at 25 °C was investigated in batch experiments. It highly depends on the supersaturation level. Both increasing supersaturation and rising concentration of the tenside promote the production of needle-like crystals but the influence of the driving force is much more pronounced. SDS increases the crystallization rate and the linear crystal growth rate in length direction of the crystals. To a high degree it also influences properties of the crystallizing solution such as surface tension and viscosity.     

Hydrothermal synthesis and formation of 4ZnO·B2O3·H2O whiskers via a new route

4ZnO·B₂O₃·H₂O whiskers were prepared from 2ZnO·3B₂O₃·3.5H₂O under hydrothermal process at 160 °C for 10 h. The synthesized product was characterized by XRD, SEM, TG‐DSC and FT‐IR. SEM results showed that the synthesized 4ZnO·B₂O₃·H₂O whiskers' length was about 3–10 μm and the diameter was 0.2–0.3 μm. Further study on the whiskers' growth process and mechanism showed that the formation of the whiskers went through three stages and the morphology of 4ZnO·B₂O₃·H₂O changed from irregular particles to rod‐like structures and finally to whiskers. The variation of the morphology of the 4ZnO·B₂O₃·H₂O whisker with the concentration of the starting material was investigated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

Crystallization and Characterization of Orthorhombic β‐MgSO4 · 7H2O

In solution, the growth rate and the crystal habit are influenced by a number of factors such as supersaturation, temperature, pH of the solution, cooling rate, agitation, viscosity, initial state of the seed crystal and the presence of impurities. The crystallization of orthorhombic β‐MgSO₄ · 7H₂O, from low temperature aqueous solution by slow cooling process was studied. The metastable zone width, the induction periods (τ) for different supersaturations and the effect of pH on the growth rate of the crystals were investigated. The increase of pH yielded bigger crystals. The structural, optical, thermal and mechanical properties of β‐MgSO₄ · 7H₂O have been studied using FT‐IR, X‐ray diffraction, TGA‐DTG and micro hardness analyses.     

Crystalloluminescence and Mechanoluminescence Spectra of Ba(ClO3)2 · H2O and 2 K2SO4 · Na2SO4 Crystals

Crystalloluminescence and mechanoluminescence of Ba(ClO₃)₂ · H₂O and 2 K₂SO₄ · Na₂SO₄ crystals are investigated. The crystalloluminescence spectra are almost similar to the photoluminescence spectra; however, they differ completely from the mechanoluminescence spectra. The crystalloluminescence excitations may take place due to the various processes: (i) the recombination of ions, (ii) from amorphous to crystalline transition, (iii) from the phase change during the crystallization, and (iv) from the dielectric breakdown by the electric field produced due to the creation of microfracture during the crystal growth. It is concluded that the crystalloluminescence excitation in Ba(ClO₃)₂ · H₂O and 2K₂SO₄ · Na₂SO₄ crystals may be chemical in origin.     

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.