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Other Salts (other + salt)
Selected AbstractsComparison of the Effects of an Ionic Liquid and Other Salts on the Properties of Electrospun Fibers, 2 , Poly(vinyl alcohol)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2009Ganesh Kumar Arumugam Abstract Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039,0.259 mol,·,kg,1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector. [source] 7Li, 31P, and 1H Pulsed Gradient Spin-Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other SaltsCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2005Ignacio Fernández Abstract 7Li, 31P, and 1H variable-temperature pulsed gradient spin-echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2-lithio-1,3-dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low-temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well-separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent-separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion. [source] Limits of life in MgCl2 -containing environments: chaotropicity defines the windowENVIRONMENTAL MICROBIOLOGY, Issue 3 2007John E. Hallsworth Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source] Calcite and gypsum solubility products in water-saturated salt-affected soil samples at 25°C and at least up to 14 dS m,1EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2010F. Visconti Calcite and gypsum are salts of major ions characterized by poor solubility compared with other salts that may precipitate in soils. Knowledge of calcite and gypsum solubility products in water-saturated soil samples substantially contributes to a better assessment of processes involved in soil salinity. The new SALSOLCHEMIS code for chemical equilibrium assessment was parameterized with published analytical data for aqueous synthetic calcite and gypsum-saturated solutions. Once parameterized, SALSOLCHEMIS was applied to calculations of the ionic activity products of calcium carbonate and calcium sulphate in 133 water-saturated soil samples from an irrigated salt-affected agricultural area in a semi-arid Mediterranean climate. During parameterization, sufficiently constant values for the ionic activity products of calcium carbonate and calcium sulphate were obtained only when the following were used in SALSOLCHEMIS: (i) the equations of Sposito & Traina for the free ion activity coefficient calculation, (ii) the assumption of the non-existence of the Ca (HCO 3)+ and CaCO3o ion pairs and (iii) a paradigm of total ion activity coefficients. The value of 4.62 can be assumed to be a reliable gypsum solubility product (pKs) in simple aqueous and soil solutions, while a value of 8.43 can only be assumed as a reliable calcite solubility product (pKs) in simple aqueous solutions. The saturated pastes and saturation extracts were found to be calcite over-saturated, with the former significantly being less so (p IAP = 8.29) than the latter (p IAP = 8.22). The calcite over-saturation of saturated pastes increased with the soil organic matter content. Nevertheless, the inhibition of calcite precipitation is caused by the soluble organic matter from a dissolved organic carbon threshold value that lies between 7 and 12 mm. The hypothesis of thermodynamic equilibrium is more adequate for the saturated pastes than for the saturation extracts. [source] Rock hyraces: a cause of San rock art deterioration?JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2007Linda C. Prinsloo Abstract San rock art sites are found throughout southern Africa, many showing signs of deterioration. In order to conserve this invaluable heritage, a long-term multidisciplinary project has been launched to monitor the rate of their deterioration and determine the various chemical processes that are possibly contributing to the decay. This study was initiated to establish if Raman spectroscopy could contribute to this project and since rock hyrax colonies live in close proximity to many of these archaeological sites, the possible influence of their metabolic products on the deterioration process was investigated. The precipitates from the urine of rock hyraces were analysed with Raman and Fourier-transform infrared (FTIR) spectroscopy. Where the urine was in contact with the faeces, the precipitates are a mixture of vaterite (a rare polymorph of CaCO3) and the hydrated salt calcium monohydrocalcite (also rarely found in nature). On areas where this contact is at a minimum the common and stable polymorph of CaCO3, calcite, is the main component. SEM micrographs and XRD analysis support the Raman and FTIR results. XRD, FTIR and preliminary GC-MS analyses of hyraceum, the fossilised mixture of faeces and urine, identified an inorganic phase (potassium chloride, with small concentrations of other salts, e.g. vaterite and weddelite) and an organic phase, which is a cocktail of various aromatic compounds, mainly amides, alcohols and acids. These compounds could contribute to the crystallisation of these rare carbonates, as well as other uncommon salts detected on the cave walls, such as syngenite. The presence of phosphates in the urine may further act as a stabilizing agent. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||