Dose response of A-type carbonated apatites prepared under different conditions

Irradiated A-type carbonated apatites with carbonate content ranging from 1.45% to 4.84% are studied by using electron paramagnetic resonance (EPR). The EPR spectra are mainly constituted of lines associated to axial CO₂⁻ species (g=2.0028 and g=1.9973) and orthorhombic CO₃⁻ species (g₁=2.0170, g₂=2.0090 and g₃=2.0041). The production of CO₂⁻ species on gamma irradiation depends on the carbonate concentration and the hydroxyapatite stoichiometry. The lowest dose detection limit was achieved with stoichiometric samples and carbonate concentration of 3.7%.     

The synthesis of apatites with an organophosphate and in nonaqueous media

The syntheses of barium, cadmium, calcium, lead, and strontium apatites were performed in anhydrous polar organic solvents such as DMSO, anisole, pyridine, glacial acetic acid, ethanol, methanol, and DMF. Reactions took place under anhydrous conditions at temperatures ranging from 80 to 120 °C and for durations of 1–6 days. Ten apatites were synthesized in nonaqueous solvents and three (PbApF, PbApCl, SrApCl) were obtained using trimethylphosphate as the phosphate source. The use of nonaqueous solvents alleviates the formation of hydrogen phosphates which occurs in aqueous solution for some divalent cations. The limited solubility of even alkali metal salts in many of the solvents also produces nonapatitic double salts such as NaPb₄(PO₄)₃, NaPbPO₄, KPb₄(PO₄)₃, Cd(OH)NO₃, and NaBaPO₄.     

A highly regular hexapod structure of lead sulfide: solution synthesis and Raman spectroscopy

A highly regular hexapod-like structure of PbS with six symmetric arms has been synthesized by a simple and mild chemical solution route. The hexapod-like PbS structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The results show that each arm is perpendicular to the other four, and opposite to the last one. The arms are about 0.3-0.6 microm long, which have about 40-60 nm tips and 150-200 nm base. And the arm shows an icicle-like structure and some clear steps, and grows along 100 directions. The most possible growth mechanism discussed herein is based on the characterization results. The Raman spectra of the hexapod-like PbS structure were investigated. The results show that our products are sensitive to the laser and can be photodegraded easily.     

The solubility of zinc dodecanoate in xylene and tetrachloromethane

Whereas zinc dodecanoate in xylene exhibits a critical solution temperature, it does not do so in tetrachloromethane.Evidence is presented which suggests that the abrupt increase in solubility in xylene is not due to a phase change of the solid zinc dodecanoate.     

Precipitation and characterization of uniform submicrometer lead titanate particles. Part II: Reaction mechanism

The chemical mechanism of the precipitation of lead titanium peroxohydroxide particles in a solution of nitrilotriacetate (NTA) complexes of lead and titanium peroxo-hydroxide is envisioned as the interaction between cations of lead hydroxide and anions of polymeric titanium peroxo-hydroxide.     

铅与硝酸反应及影响因素

铅与硝酸的反应比较复杂,在无机化学教材和相关资料中对铅与硝酸反应的阐述不一致,这将不利于学生在无机化学学习中对铅的基本性质的掌握。针对无机化学教材中存在的问题,本文通过大量实验探究了铅与硝酸反应的条件以及硝酸浓度、反应温度、反应时间等对铅与硝酸反应的影响,并考查了硝酸铅在不同浓度硝酸中溶解度的变化,利用红外光谱(IR)和X射线粉末衍射(XRD)对铅与浓硝酸的反应产物进行了表征,明确了铅易溶于稀硝酸而在浓硝酸中溶解度小的实质。     

The solubility of water in mixtures of dimethyl ether and carbon dioxide

This paper reports measurements of the solubility of water in liquid and supercritical fluid mixtures of dimethyl ether and carbon dioxide. The measurements were made by extracting water under saturation conditions using premixed liquid dimethyl ether–carbon dioxide mixtures. Results are reported for temperatures of 313.8 K and 333.3 K at 9.0 MPa and 15.0 MPa. Results are fitted to the Peng–Robinson cubic equation of state with mixing rules according to Wong and Sandler, using binary interaction parameters fitted to the literature data for the respective binary systems: dimethyl ether–water; dimethyl ether–carbon dioxide; and carbon dioxide–water. Liquid densities for dimethyl ether–carbon dioxide mixtures, measured using a coriolis flow instrument, are also reported.     

NMR study on solubility of benzyl alcohol and its transfer free energy from D_2O to cationic micelle

A new kind of surfactant, [CnH_(2n+1)OCH2CH(OH)CH2N(CH3)3]Cl (n=12, 14, 16) was synthesized. The solubility of benzyl alcohol in micellar solutions was determined by 1H NMR method. The results indicate that the length of alkyl chains of surfactant affects the solubility of ben-zyl alcohol in 2.5 × l0~(-2) mol/L micellar solutions. The solubility of benzyl alcohol per liter of micellar solution is 0.095 mole for n=12, 0.115 mole for n=14, 0.165 mole for n=16. The transfer free energy of benzyl alcohol from aqueous phase to micellar phase is -24.29 kJ/mol for n=12, -24.37 kJ/mol for n=14, -24.49 kJ/mol for n=16.     

Review of the use of NMR spectroscopy to investigate structure,reactivity, and dynamics of lead soap formation in paintings

Heavy metal carboxylate or soap formation is a widespread deterioration problem affecting oil paintings and other works of art bearing oil-based media. Lead soaps are prevalent in traditional oil paintings because lead white was the white pigment most frequently chosen by old masters for the paints and in some cases for the ground preparations, until the development of other white pigments from approximately the middle of the 18th century on, and because of the wide use of lead-tin yellow. In the latter part of the 19th century, lead white began to be replaced by zinc white. The factors that influence soap formation have been the focus of intense study starting in the late 1990s. Since 2014, nuclear magnetic resonance (NMR) studies have contributed a unique perspective on the issue by providing chemical, structural, and dynamic information about the species involved in the process, as well as the effects of environmental conditions such as relative humidity and temperature on the kinetics of the reaction(s). In this review, we explore recent insights into soap formation gained through solid-state NMR and single-sided NMR techniques.     

The lead amalgam/lead sulfate electrode redesigned and reassessed

To make the (Pb)Hg‖PbSO₄‖SO ₄ ²⁻ electrode really usable and attractive for extensive application to thermodynamic studies, a new, simplified design and a convenient preparative procedure have been introduced, ensuring stable amalgams and reproducible electrode potentials. The electrode so prepared has been exhaustively characterized both thermodynamically and as a SO ₄ ²⁻ -sensing electrode, in different sulfate solutions, including H₂SO₄. The past discrepancies of standard potentials-mainly due to preparation and/or handling problems-are discussed and, for a final resolution of the question, a practical standardization procedure is proposed.     

Synthesis of two new chloro derivatives of the guaianolide grossmisin and the crystal structure of one derivative

The reaction of grossmisin (8α-hydroxyachillin,1) with chlorine in benzene afforded a mixture of products. The less polar product readily crystallized after chromatography. According to the X-ray diffraction data, this product has the structure of 1α,10β-dichloro-1,10-dihydrogrossmisin. The second chloro derivative of grossmisin,viz., 8β-chloroachillin, was prepared in good yield by the reaction of lactone1 with PCl₅ in CHCl₃ in the presence of Py. Published inIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 11, pp. 1932–1934, November, 2000.     

The diffusion and solubility of Irganox 1098 in polyamide 6

Diffusion coefficients (D) and solubilities (S) of a phenolic antioxidant (Irganox^® 1098) in polyamide 6 were determined in the temperature range of 139-180 °C. D and S show Arrhenius and van’t Hoff dependences on temperature respectively, with discontinuities at the melting temperature of the antioxidant. The activation energies for diffusion and enthalpies of solution are lower above than below the melting temperature. Based on the determined parameters for diffusion and solubility, the blooming of Irganox^® 1098 as a function of temperature and time was calculated.     

The solubility of barite and celestite in sodium sulfate: Evaluation of thermodynamic data

The solubilities of barite [BaSO₄(c)] and celestite [SrSO₄(c)] in Na₂SO₄ were studied and found to be significantly lower than the experimental values reported in the literature. Our new solubility data are in excellent agreement with the predictions of ion interaction models, which have previously been parameterized primarily from solubility data obtained in chloride media. Our solubility data were analyzed both in terms of aqueous thermodynamic models that included ion association species and in terms of ion interaction models that did not require the explicit recognition of such species. In the case of SrSO₄, although both ion association and ion interaction models can accurately model our solubility data, the ion interaction approach is preferred because it is easier to extend to higher concentrations. In the case of BaSO₄, the aqueous ion interactions appear to be stronger than those for SrSO₄, and so the explicit recognition of a BaSO₄(aq) ion association species is preferred. The logarithms of the thermodynamic solubility products (log K _sp ) for celestite and barite were –6.62±0.02 and –10.05±0.05, respectively. When the data were analyzed using models that include ion association species, the logarithms of the thermodynamic equilibrium constants for the SrSO₄(aq) and BaSO₄(aq) association reactions were 1.86±0.03 and 2.72±0.09, respectively.     

Synthesis and crystal structure of triphenyltin and lead complexes with organic peroxides

Crystalline triphenyltin cumyl and tert-butyl peroxides (Ph₃SnOOCMe₂Ph and Ph₃SnOOBu^t, respectively) and triphenyllead cumyl peroxide (Ph₃PbOOCMe₂Ph) were synthesized and characterized by single crystal and powder X-ray diffraction, NMR, FTIR and Raman spectroscopies, TG and DSC analysis. The formation of triphenyltin tert-butyl peroxide in benzene in the presence of a base was proved by ¹¹⁹Sn, ¹³C and ¹H NMR spectroscopy. To the best of our knowledge, the obtained complexes are the first structurally characterized coordination compounds of tin and lead with organic peroxides.     

Study on electrochemical properties of Pb(BF4)2 electrolyte for improvement of cycle lifetime and efficiency in soluble lead flow batteries

The electrochemical characteristics of a soluble lead flow battery are key factors for the improvement of its cyclic lifetime and efficiency. In this work, we suggested aqueous solution of Pb(BF₄)₂ and HBF₄ as the electrolytes of soluble lead flow battery and observed the kinetic behavior of the electrode by cyclic voltammetry of the cyclic lifetime, quantum efficiency and voltage efficiency of the SLFB with respect to concentration of the electrolyte. Both the density and viscosity of the electrolyte increase with an increasing [Pb(BF₄)₂]. The conductivity exhibits a peak at 1.5 mol/L Pb(BF₄)₂ when [HBF₄] is below 1.0 mol/L. According to the cyclic voltammetry, the electrode process is fast with a low overvoltage and no additional reactions for the aqueous solution with 1.5 mol/L Pb(BF₄)₂ and 0.25 mol/L HBF₄. Overall, for the aqueous solution of 1.5 mol/L Pb(BF₄)₂ and 0.25 mol/L HBF₄, the battery showed a best performance with the cyclic lifetime being 48 times, the average quantum efficiency 88%, the voltage efficiency 70% and the battery efficiency 62%. These results are promising for fresh parameters of the electrolyte that could play a major role for the improvement of SLFBs.     

Role of relativistic effects in the electronic structure and chemical bond of lead hexacyanoferrate

The electronic structure of a large fragment of the Pb₂Fe(CN)₆ crystal lattice with the trigonal structure is studied in the framework of a fully relativistic discrete variational cluster method. On the basis of comparing the results obtained with the data of previous non-relativistic calculations we have considered the relativistic effects on the electronic energy spectrum, the charge density distribution, and Pb-N, N-C, and C-Fe chemical bonding.     

Molecular structure of 2-(hydroxyimino)propanohydroxamic acid in solid state and DMSO solution

The 1H and 13C NMR spectra of 2-(hydroxyimino)propanohydroxamic acid (hpha) were measured in DMSO-d6 solution. The set of several monomeric structures along with the cluster of H-bonded hpha with three DMSO molecules were proposed to fit the experimental data. The calculated chemical shifts [B3LYP/6-311++G(d,p)] strongly suggested the formation of the cluster in which all the labile protons were H-bonded to the solvent molecules. The comparison between experimental and calculated Raman spectra of hpha in DMSO also suggested that in these conditions the investigated compound forms the proposed cluster rather than dimers. According to our calculations [B3LYP/6-31+G(d)] this cluster was energetically stabilized (84-106 kJ mol-1) compared to postulated dimeric structures. On the other hand, formation of dimers was proposed to be present for hpha in solid state. The comparison of the vibrational data (IR, RS) with the computed harmonic frequencies of three most probable dimers [B3LYP/6-31+G(d)] suggested that the dimer in which molecules adopted the zEe-keto form and were linked by two symmetric, almost linear H-bonds between the carbonyl oxygen atoms and the hydroxamic O-H protons was the predominant species of hpha in the solid state. Thus, the structures of hpha in solid state and DMSO solution appeared to be different.     

Hexafluorosilicates of bis(aminopyridinium). The relationship between H-bonding system and solubility of salts

Pyridinium hexafluorosilicates of the composition (LH)₂[SiF₆] (I, II, IV, L = 2-aminopyridine, 3-aminopyridine, and 2,6-diaminopyridine) and (LH)₂[SiF₆]·H₂O (III, L = 4-aminopyridine) were separated as crystalline products of interaction of fluorosilicic acid with relevant aminopyridines. The compounds were characterized by IR, mass-spectrometry, potentiometry, solubility data, and in the case of I and IV by X-ray crystallography. The relationship between the salts structure and some physical properties is discussed.     

Air stable liquid clathrates: Solid state structure and hydrocarbon solubility of organic cation triiodide salts

A series of air and water stable organic cation triiodide salts have been prepared and characterized. Almost all of the salts isolated sustain liquid clathrate phases in the presence of benzene or toluene, the compositions of which were determined via¹H NMR spectroscopy. Two of the salts were also characterized via X-ray crystallography in order to determine the nature of any solid state interionic interactions (1-ethylpyridinium triiodide, monoclinic,P2₁/c,a = 9.6031(7),b = 15.129(3),c = 8.8160(16) Å, = 104.192(11)°,Z = 4,R = 0.041 for 2463 independent observed reflections; 1,2,4-trimethylpyridinium triiodide, orthorhombic,Pbcm,a = 9.434(4), 20.176(4), 7.411(4) Å,Z = 4,R = 0.045 for 966 observed reflections).     

The solubility and solvation of salts in mixed nonaqueous solvents. 1. Potassium halides in mixed aprotic solvents

The solubilities of potassium fluoride, chloride, and bromide in acetonitrile, N,N-dimethylformamide, and dimethylsulfoxide and in binary mixtures of these solvents were determined at 25°C. The standard molar Gibbs free energies of solution, _solnG°, in the neat solvents were related to the polarizabilities and basicities of the anions and the dipole moments and acidities of the solvents. The values of _solnG° in the mixtures were fitted by expressions from the quasi-lattice quasi-chemical theory. The mean number of each kind of solvent in the nearest environment of the ions was obtained from these results.