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Aluminium as a growth limiting factor has been recognized for many years. At high concentrations, aluminium (Al) ions reduce nutrient availability in soils, harm plant cells and thus inhibit plant growth. In addition, Al concentration may be a major factor filtering species composition on acid soils in favour of Al-resistant plants. In this study we analyse species responses and turnover along soil pH and Al gradients and we attempt to interpret the results with respect to the recognised aluminium solubility patterns. Plant community and soil data collected from mesophilous and acidophilous submontane broad-leaved forests of Western Slovakia were used for this purpose. Topsoil horizons were analysed for soil reaction (pH), organic carbon and extractable total aluminium. Species responses to the Al measurements were analysed and tested using CCA and the Huisman-Olff-Fresco (HOF) model. We calculated species turnover by accumulating the first derivatives of all HOF response curves, and interpreted them with respect to the Al solubility pattern observed in the soil dataset. We also performed a bioindication experiment to test how a species assemblage indicates the aluminium gradient. In total, 81% of species shows a significant response to the soil Al gradient. We identified that a rapid retreat of many species and, in consequence, high compositional turnover (ecotone) corresponded with a discontinuity in Al solubility observed at 130 mg Al kg−1 (pH 3.8). Here, the exchangeable Al became increasingly under-saturated with respect to the equilibrium attained at higher pH. This discontinuity was also visible in the bioindication experiment, where the prediction algorithm operated better at the acidic end of the gradient. The results indicate that the studied plant assemblages respond sensitively to soil Al solubility. Changes in aluminium solubility in soils correspond with ecotone between adjacent types of vegetation.

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Journal of Thermal Analysis and Calorimetry
Authors: S. C. Mojumdar, G. Madhurambal, M. Mariappan, and B. Ravindran

were synthesized, grown by slow evaporation technique at room temperature and studied by thermodynamic, microscopy, optical analysis and solubility test. Experimental procedure There are several methods of measuring the

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Abstract  

A simple method for determination of the hydrate numbers of saturating multi-hydrate salts in developed. The method demonstrated for scandium sulfate is based upon estimation of the enthalpy of solution of the hydrates from the solubility smoothing equations. It is shown that in the Sc2(SO4)3–H2O system, contrary to common opinion, the equilibrium solid phases are: Sc2(SO4)3.6H2O at 273–295 K, Sc2(SO4)3.5H2O at 295–333 K and Sc2(SO4)3.4H2O at 333–373 K. The solubility smoothing equations for the hexa-, penta- and tetrahydrate of scandium sulfate are given.

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Solubility diagrams in solvent-antisolvent systems by titration calorimetry

Application to some pharmaceutical compounds in water-ethanol mixtures

Journal of Thermal Analysis and Calorimetry
Authors: M. Hamedi and J. Grolier

Abstract  

Isothermal titration calorimetry (ITC) has been used to develop a method to construct the solid-liquid equilibrium line in ternary systems containing the solute to precipitate and an aqueous mixed solvent. The method consists in measuring the heat of dissolution of a solid component (the solute) during successive additions of the liquid solvent. The cumulated heat, resulting from the successive heat peaks obtained for the different injections of known volumes of solvent, plotted vs. the ratio of the numbers of moles n solvent/n solute is represented by two nearly straight lines. The intercept of the two lines gives the solubility limit and the corresponding enthalpy of dissolution of the solute in the solvent. Solubility diagrams have been established at 303.15 K in binary mixed solvents ethanol-water over the whole concentration range for seven compounds of pharmaceutical interest, namely: urea, phenylurea, l-valine, dl-valine, l-valine ethyl ester hydrochloride, tris(hydroxymethyl)amino methane.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Hasilkar, N. Khedekar, Keshav Chander, A. Jadhav, and H. Jain

Abstract  

Studies have been carried out on the solubility of Pu(III) oxalate by precipitation of Pu(III) oxalate from varying concentrations of HNO3/HCl (0.5–2.0M) solutions and also by equilibrating freshly prepared Pu(III) oxalate with solutions containing varying concentrations of HNO3/HCl, oxalic acid and ascorbic acid. Pu(III) solutions in HNO3 and HCl media were prepared by reduction of Pu(IV) with ascorbic acid. 0.01–0.10M ascorbic acid concentration in the aqueous solution was maintained as holding reductant. The solubility of Pu(III) oxalate was found to be a minimum in 0.5M–1M HNO3/HCl solutions containing 0.05M ascorbic acid and 0.2M excess oxalic acid in the supernatant.

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A rapid and simple method has been developed for the determination of Mn, Zn, Cr and Ag by radiochemical thermal neutron activation analysis, involving solvent extraction and precipitation technique. Mn, Zn, Cr and Ag can be determined with an accuracy of 8.9, 5.8, 7.7 and 7.6%, respectively. The method has been employed for determination of the elements in fish solubles. Two samples and a standard can be analyzed in three hours.

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Abstract  

Purposes of this paper were to prepare and study new drug delivery systems for both flavanone glycosides and their aglycones based on solid-dispersion systems. These compounds are poor water soluble drugs, so an enhancement of their dissolution is a high priority. Solid-dispersion systems were prepared using PVP, PEG and mannitol as drug carrier matrices. Characterizations of these dispersions were done by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The glass transition (T g) temperature of PVP was only recorded in the DSC thermograms of PVP solid-dispersions of both flavanone glycosides and their aglycones, while in case of PEG and mannitol solid-dispersions endotherms of both glycosides and aglycones were noticed with low peak intensity, indicating that high percent of drug is in amorphous state. The XRD patterns of all PVP solid-dispersions of aglycones show typical amorphous materials, but XRD patterns of their glycosides reveal the presence of crystalline material. However, in all solid dispersions shifts in T g of PVP as well as T m of PEG were observed, indicating the existence of some interactions between drugs and matrices. SEM and TEM microscopy revealed that PVP/aglycone flavanone compounds are nanodispersed systems while all the other solid dispersions are microcrystalline dispersions. The solubility of both flavanone glycosides and their aglycones was directly affected by the new physical state of solid dispersions. Due to the amorphous drug state or nano-dispersions in PVP matrices, the solubility was enhanced and found to be 100% at pH 6.8 in the nano-dispersion containing 20 mass% of aglycones. Also solubility enhancement was occurred in solid dispersions of PEG and mannitol, but it was lower than that of PVP nano-dispersions due to the presence of the drug compounds in crystalline state in both matrices.

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1028 1030 Nagahama, M., Nomura, S., Ozaki, Y., Yoshimura, C., Kagawa, H., Fukuhara, S.: Platelet activation markers and soluble adhesion molecule in patients with systemic lupus

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Abstract  

For the GaSb single crystals doped with copper (grown using the Czochralski method without encapsulant in flowing atmosphere of hydrogen) the distribution coefficient of copper in GaSb,k eff=0.0021±0.0006 was found and the copper solubility in GaSb was discussed. The region of copper solubility in GaSb was analyzed on the thermodynamic basis using chemical phase diagram in the Sb−Ga−Cu system. Due to a rather low solubility of copper, its excessive amount in GaSb caused probably an increase of the dislocation density at the end of the GaSb single crystals.

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Ergocalciferol, cholecalciferol, (±)-α-tocopherol, tocopherol acetate, retinol, retinol acetate, retinol palmitate, menadione, and phytonadione have been investigated on RP8F 254s and RP18F 254s TLC plates with methanol-water in different volume proportions as mobile phases. Linear relationships were obtained between the R M values of the fat-soluble vitamins and the volume fraction of methanol in the mobile phase. Retention values, R M , were extrapolated to zero methanol content and the lipophilicity values R MW(RP8) and R MW(RP18) obtained were compared with measured partition coefficients (log P exp ) and partition coefficients (AlogPs, AClogP, AB/logP, COSMOFFrag, milogP, Kowwin, xlogP) calculated using seven different software products. Cluster analysis was also used for comparison of the theoretical partition coefficients with the chromatographic lipophilicity ( R MW(RP8) and R MW(RP18) ) of the fat-soluble vitamins. It was found that lipophilicity values R MW(RP8) were most similar to AClogP whereas R MW(RP18) was most similar to the theoretical partition coefficient Kowwin. R MW(RP8) and R MW(RP8) values (i.e. values obtained on RP8F 254s and RP18F 254s plates) closely describe the lipophilic properties of fat-soluble vitamins.

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