Modeling Thermodynamics and Phase Equilibria for Aqueous Solutions of Trisodium Phosphate

A computational model is developed to calculate thermodynamic phase equilibria in alkaline solutions of trisodium phosphate up to 100°C. A variety of data are used, including isopiestic measurements, freezing point data, vapor pressure data at 100°C, heat capacities, heats of dilution, and solubility measurements. Pitzer's ion-interaction treatment is used to model electrolyte solutions and many unknown parameters are determined from existing data through nonlinear least-squares fitting. Phase equilibria are determined by minimization of total Gibbs energy using a modification of the code SOLGASMIX. Results calculated using the model accurately predict experimental data.     

凝胶扩散体系中磷酸钙的沉淀图形

０引言生物矿化可分为正常矿化和异常矿化。胆结石是一种生物异常矿化，是世界性的常见病和多发病，形成机理尚不十分清楚。从结石的形成过程来看，不仅结石的组成与其形成机理有关，而且结石的组成分布和剖面图形同样与之有密切关系。人们经常可以观察到，一类结石的剖面具有周期环状图形，且棕色和乳白色环相间。其中白色环的主要成份为胆固醇；棕色环的主要成份为胆红素钙络合物，同时棕色环中还常常含有少量的磷酸钙和碳酸钙等无机难溶盐。由于结石的形成是一个长期的过程，研究表明在结石生长的过程中胆汁的组成不发生规律性的周期变化…     

Synthesis of Calcium Phosphate and Calcium Silicate Composites

A one-step method for preparing composites based on calcium phosphates (CPs) and calcium silicates (CSs) with variable contents of the components is proposed. The combination of chemical analysis, X-ray powder diffraction, and simultaneous thermal analysis with mass-spectrometric detection (STA-MS) showed that the coprecipitation of salts from aqueous solutions yielded mixtures of poorly crystallized carbonate hydroxyapatite (CHA) and xonotlite with minor calcite. Scanning electron microscopy and low-temperature nitrogen adsorption showed that nanosized crystallites of these phases during crystallization were combined into mesoporous aggregates (the mean pore size was 6–11 nm) to form micrometer-sized bulk structures with a developed surface. Two-hour calcination of synthesis products at 1000°С yielded mixtures of well-crystallized Са₁₀(РО₄)₆(ОН)₂ and β-CaSiO₃.     

Investigation Under Physiological Conditions of Orotic Acid Complex Equilibria with Calcium and Magnesium Using Potentiometric and Spectroscopic Techniques

With a view to obtaining information about the structures and stabilities of the orotic acid (ORA, vitamine B₁₃) complexes with Ca(II) and Mg(II), potentiometric and spectroscopic studies using a glass electrode have been carried out in aqueous solution at physiological conditions (37 ^∘C, 0.15 mmol⋅dm⁻³ NaCl) and at different ligand to metal ratios. Computer-assisted analysis of the potentiometric titration data within the 2.5–9.5 pH range yielded equilibrium constants for both systems. Several different complexes were separately considered during the calculation procedure for both systems, but evidence was found only for the mononuclear species ML. Speciation calculations based on the determined constants were then used to plan experiments with IR and UV spectroscopic techniques, which led to the determination of the related structures.     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

Modeling of Equilibria in Complex Cryolite Melts

Summary. In the fully ionized sodium sulfate melt, the solubility of an oxide (at a given melt basicity) is well described by considering a single equilibrium to form a specific simple acidic or basic solute. In this case, the dominant solutes are identified by a simple log–log interpretation describing the dependence of the solute concentration on an acid-base parameter . However, in fused cryolite (Na₃AlF₆) solutions, the solvent itself and the solutes of oxides involve anionic complexes (alumino-fluorides and oxy-fluorides). Therefore, a single simple equilibrium does not suffice to model the complex solution. Rather, as for a high temperature multi-component gas phase containing many complex volatile species, every possible equilibrium must be individually satisfied and coupled to a mass balance. Examples will be given for each limiting type of solution behavior.     

Modeling of Equilibria in Complex Cryolite Melts

In the fully ionized sodium sulfate melt, the solubility of an oxide (at a given melt basicity) is well described by considering a single equilibrium to form a specific simple acidic or basic solute. In this case, the dominant solutes are identified by a simple log–log interpretation describing the dependence of the solute concentration on an acid-base parameter loga_{Na2 O}\log a_{\rm Na_2 O} . However, in fused cryolite (Na₃AlF₆) solutions, the solvent itself and the solutes of oxides involve anionic complexes (alumino-fluorides and oxy-fluorides). Therefore, a single simple equilibrium does not suffice to model the complex solution. Rather, as for a high temperature multi-component gas phase containing many complex volatile species, every possible equilibrium must be individually satisfied and coupled to a mass balance. Examples will be given for each limiting type of solution behavior.     

土壤和水体中铝的化学平衡

详细综述了土壤环境中铝的形态及三大化学平衡：沉淀溶解平衡、水解平衡、络合平衡。     

Thermodynamic Constants of Acid-Base Equilibria in Solutions of Penicillins

The constants of acid-base equilibria in solutions of benzylpenicillin, carbenicillin, and ampicillin at 20°C were determined by pH-metric titration (supporting electrolytes 0.1, 0.4, 0.7, and 1.0 M KCl and KNO₃). The sizes of the ionic species of the penicillins in their energetically favorable conformation were determined by the PM3 semiempirical method. The thermodynamic equilibrium constants were estimated by extrapolation of the concentration constants to zero ionic strength by the Huckel equation, taking into account the calculated sizes of the ions.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 1049–1054.Original Russian Text Copyright © 2005 by Alekseev, Demskaya, Dodonova.     

化学平衡的多重性、稳定性和重现性

利用动力学方法讨论了非理想的化学反应体系中化学平衡态的多重性、稳定性和实验上的可重现性。分析了实验结果(化学平衡态)与初始条件以及其它动力学过程之间的依赖关系,并简略讨论了化学平衡多重性和稳定性问题在某些实际问题和工程设计中的重要性。     

Density and Viscosity of Sodium Phosphate Solutions

The density and viscosity of sodium phosphate solutions with a concentration of 30–41.6 wt % at 70–100°C were determined.     

Biological and Medical Applications of Calcium Phosphate Nanoparticles

Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.     

Peculiarities of Thermochemical Investigations of Acid-Base Equilibria in Complexon Solutions

Polymorphic transitions of α-phenylcinnamic acid stereoisomers crystallized from various solvents (CHCl3, ethanol, diethyl ether), precipitated with different acids (acetic acid or HCl) or sublimed have been studied by differential scanning calorimetry (DSC). Measurements were also supplemented by powder X-ray diffractometry (XRD). Polymorphic transitions were not found for any of the E isomer samples irrespective of the method of treatment. However, in heating-cooling cycles reversible transitions could be detected for the Z isomer. On heating an exothermic peak was registered on samples sublimed, crystallized from ethanol or diethyl ether before melting, while samples precipitated by HCl or crystallized from chloroform exhibited more complex transitions. Here, endothermic effects were also observed. Enthalpy values for transformations (either for melting or polymorphic and other transitions) are also given. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of Calcium Phosphate Nanoparticles in Collagen Medium

Summary: Mineralization of the proteic matrix composed mostly of collagen type I is controlled by specific interactions of ions Ca²⁺ and PO, present in the biological fluid, with the matrix, and by the diffusion of these ions. The specific interactions and the diffusion of ions combined; result in the nucleation and formation of calcium phosphate particles. Moreover, they control the morphology, size, crystallinity and composition of the particles. In this work, precipitation of calcium phosphate particles in a collagen matrix type I was carried out through impregnation of the matrix with a Ca²⁺ and PO solution, with Ca/P ratio 1.67 and pH 2.5. Precipitation of particles associated with matrix structuring was carried out by adsorption of gaseous ammonia.     

Mechanisms of Calcium and Phosphate Ion Association in Aqueous Solution

The initial steps of nucleation of calciumphosphates in aqueous solution are elucidated by means of quantum / classical molecular mechanics simulations. A special focus is dedicated to the role of the protonation state of the phosphate ion. The crystallization of calciumphosphates including entirely deprotonated phosphate ions is found at much lower pH values than required for finding the (PO₄)^3? species in water. In such cases the depronation of the hydrogenphosphate ion has to occur during crystal growth. According to our findings, the [Ca²⁺··(PO₄)^3?··Ca²⁺] ion triple is the smallest stable aggregate, which may be expected to contain an entirely deprotonated phosphate ion.     

胆盐与磷酸钙的相互作用

胆汁的pH条件下(pH=6～8)，应该生成无定形磷酸钙(ACP)，而在胆结石中磷酸钙通常以羟基磷灰石的形式出现.利用谱学方法研究了ACP与胆盐的作用.结果表明，胆盐以胶团的形式与ACP作用，在溶液中形成复合胶团，使其溶解度增加.不同类型胆盐与ACP的作用能力不同：脱氧胆酸钠(NaDC) > 牛磺胆酸钠(NaTC) > 胆酸钠(NaC).胆盐与ACP中结合钙的亲和能力大于结合钙的亲和能力，使ACP在胆汁的环境下容易转化为羟基磷灰石.     

Thermodynamics of Protolytic Equilibria in Aqueous Solutions of Biologically Active Ligands

The protolytic equilibria in aqueous solutions of different amino acids and dipeptides were studied by a direct calorimetric method at 288–328 K. The measurements were made with an isothermal-shell calorimeter with automatic temperature recording. The thermodynamic characteristics of the processes of acid-base equilibria were found from the combined results of thermochemical measurements and equilibrium constant data. Gurney concepts were used to analyse the thermodynamic characteristics of reactions. Comparisons of the temperature-dependent and temperature-independent contributions to the Gibbs energy and enthalpy change afford the criteria of the variability in sign of the ΔH of the process, i.e. they allow prediction of the magnitude of the temperature θ at which ΔH = 0. This revised version was published online in August 2006 with corrections to the Cover Date.     

热力学在无机化学“四大平衡”教学中的应用

利用化学反应吉布斯自由能变化?_rG_m~?来计算无机化学"四大平衡"的平衡常数,解释诸如沉淀-溶解平衡教学中为什么要求微溶强电解质等问题,并从化学反应等温式类推了电极反应的等温式,推导了复杂电极的标准电极电势与其简单电极的标准电极电势之间的关系,拓展了热力学在现行基础化学教学上的应用范围。