Junyan Gao  Chuang Xie  Yanlei Wang  Zhao Xu  Hongxun Hao 《Crystal Research and Technology》2012,47(4):397-403

In this paper, the solubility of trisodium citrate dihydrate and trisodium citrate pentahydrate in water was experimentally determined. From solubility data, it was found that the relationship between trisodium citrate dihydrate and trisodium citrate pentahydrate is enantiotropic with a transition temperature at 315.4±1.0 K. Different hydrates can be isolated safely by controlling the crystallization temperature. The induction periods of trisodium citrate pentahydrate in aqueous solution were measured at different temperatures. The crystal–solution interfacial energy was calculated by using classical nucleation (CL) theory, mononuclear (MN) and polynuclear (PL) mechanisms through the relationship between induction period and supersaturation. It was found that the interfacial energy values calculated by using the CL theory and the MN model are nearly the same while interfacial energy calculated by PN model are about 40% higher. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

T. Aichele 《Crystal Research and Technology》2007,42(5):419-423

Results are presented to identify the fields of primary crystallisation of red and blue potassium molybdenum oxide bronzes K_0.30MoO₃ and K_0.33MoO₃ in the ternary system K₂MoO₄–MoO₃–MoO₂. Starting from crystal growth experiments for the preparation of bronze crystals by electrolytic reduction the binary marginal systems K₂MoO₄–MoO₃ as well as MoO₃–MoO₂ and further pseudo‐binary sections have been investigated by differential thermo‐analysis, hot‐stage microscopy, and by quenching experiments under inert gas. We succeeded in determining phase transition temperatures in the binary section Mo₄O₁₁–K₂Mo₂O₇. Temperature and composition ranges have been found in this section to crystallise red and blue potassium molybdenum oxide bronzes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

N. R. Cordisco  D. B. Litvin 《Journal of Applied Crystallography》2004,37(2):346-346

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Jonathan A. Mettes  J. Brandon Keith  Richard B. McClurg 《Acta Crystallographica. Section A, Foundations and Advances》2004,60(6):621-636

A method is described to produce global phase diagrams for single‐component molecular crystals with separable internal and external modes. The phase diagrams present the equilibrium crystalline phase as a function of the coefficients of a general intermolecular potential based on rotational symmetry‐adapted basis functions. It is assumed that phase transitions are driven by orientational ordering of molecules with a fixed time‐averaged shape. The mean‐field approximation is utilized and the process begins in a high‐temperature disordered reference state, then spontaneous symmetry‐breaking phase transitions and phase structure information at lower temperature are sought. The information is mapped onto phase diagrams using the intermolecular expansion coefficients as independent variables. This is illustrated by global phase diagrams for molecules having tetrahedral symmetry (e.g. carbon tetrachloride, adamantane and white phosphorus). Uses of global phase diagrams include crystal structure data mining, guidance for crystal design and enumeration of likely or missing polymorphic structures.  相似文献   

    

David K. Tshudy  Daniel B. Litvin 《Journal of Applied Crystallography》1998,31(6):973-973

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V.S. Sistla  Jan von Langermann  H. Lorenz  A. Seidel‐Morgenstern 《Crystal Research and Technology》2014,49(7):514-520

Differences in physical‐chemical properties of diaste‐reomeric salts allow the separation into the respective salts and subsequently into enantiomers by crystallization. Within this study unusual deviations in the cation‐/anion‐ratio of a diastereomeric salt pair were observed and characterized. While the n‐salt (L‐serine benzyl ester 2,3‐toluyl‐D‐tartrate) crystallizes in a ratio of two cations and one anion, the p‐salt (D‐serine benzyl ester 2,3‐toluyl‐D‐tartrate) consists of only one cation and one anion. Consequently the classical definition of a diastereomeric salt pair does not apply. In this contribution all differences in relevant thermodynamic properties of the unusual resulting diastereomeric salt pair are presented and discussed.  相似文献   

    

C. N. Nanev  I. L. Dimitrov  F. V. Hodzhaoglu 《Crystal Research and Technology》2011,46(2):119-126

Insulin is the only protein that is secreted in a crystalline form in a human healthy body. To mimic the secretion process we used NaCl salting‐out to growing tiny rhombohedral Zn‐insulin crystals. The dissolution of the insulin crystals is of special interest for the therapeutical praxis, because the human body is supplied with the physiologically active monomers of the insulin through dissolution of the crystalline granules secreted in the pancreatic β‐cells. Sets of tiny rhombohedral Zn‐insulin crystals, which resembled the granules secreted in the β‐cells, were subjected to dissolution in blood plasma and model solutions. The impacts of the solution composition, flow rate, pH and ionic strength on the insulin crystal dissolution were investigated. The effect of the blood plasma was determinant because it dissolved the rhombohedral Zn‐insulin crystals almost instantly, while the effects of solution's physicochemical characteristics were of minor importance. In addition, we found that the presence of abundant zinc ions suppressed the dissolution of the insulin crystals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

K. Renuka Devi  K. Srinivasan 《Crystal Research and Technology》2011,46(12):1265-1272

Glycine phosphite (NH₃CH₂COO.H₃PO₃), a potential ferroelectric material, was grown as single crystals from aqueous solutions by slow evaporation and slow cooling methods. Laboratory synthesized title compound was purified by recrystallization method and confirmed by Fourier transform infrared and Laser Raman studies. Temperature dependent solubility in double distilled water in the range between 288 and 328 K was determined by gravimetric method. Morphological importance of various growth faces were studied by optical goniometry. Powder x‐ray diffraction study performed on the grown crystals confirms the crystal system and lattice parameters of the unit cell. Optical transparency of the grown crystals in the ultraviolet–visible ‐near infrared region was studied by spectroscopic method. Thermal stability of the grown crystals in the temperature region above ambient until melting was studied using differential scanning calorimetry. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Zhihua Li  Ran Zhang  Yaohuan Wu  Bo Tang  Guochun Zhang 《Journal of Applied Crystallography》2015,48(6):1665-1671

The diagram of phase equilibria in the BaB₂O₄–NaF system has been used to deduce the relationship between the cooling speed (ΔT), the pulling speed (v), the crystal radius (R_s), the slope of liquidus (m), the solution component (x) and the total quantity of melt, namely ΔT = 0.00159R_s²vmx²/G. The theoretical curves of the crystal thickness dependence on cooling rate and pulling rate have also been drawn. Under the guidance of the deduced formulas, the controlled growth of β‐BaB₂O₄ (BBO) crystals to a desired size has been achieved. A typical as‐grown BBO crystal with dimensions of Ø76 × 33 mm (525.25 g) has been grown successfully by using the high‐temperature top‐seeded solution growth method. The measured optical homogeneity indicates that the as‐grown BBO crystal has high optical quality (Δn≃ 6.9 × 10⁻⁶). The experimental curves of the crystal thickness versus the cooling rate and pulling rate were in line with the theoretical curves. The phenomenon of diameter shrinkage in the crystal growth has also been explained according to theory and practice. The theoretical derivation and experimental results provide the rationale for further growth of large BBO crystals with high optical quality.  相似文献   

    

A. Kandasamy  R. Mohan  M. Lydia Caroline  S. Vasudevan 《Crystal Research and Technology》2008,43(2):186-192

Nucleation parameters such as solubility, induction period, interfacial energy and metastable zone width have been investigated for the aqueous solution growth of a semi‐organic nonlinear optical (NLO) material of L‐Proline cadmium chloride monohydrate (L‐PCCM) single crystal. Metastable zone width and induction period values were determined experimentally in order to optimize the growth parameters. The grown crystals are transparent (dimensions: 16 x 8 x 5 mm³) and characterized by powder X‐Ray Diffraction and dielectric studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献