Aqueous Calcium Chloride Research Articles

Cyclic voltammetric and potentiometric behavior of tetracyanoquinodimethane polymer film electrodes: Effect of the nature and the concentration of the supporting electrolyte

Polymeric tetracyanoquinodimethane film electrodes were studied using cyclic voltammetry and potentiometric methods as a function of supporting electrolyte concentration in aqueous solutions of lithium chloride, alkaline earth chlorides, and acetonitrile solutions of tetra-n-butylammonium perchlorate. Charge transport rates through the films decrease dramatically as the concentration of the supporting electrolyte is increased. Films that were partially reduced in aqueous lithium or calcium chloride solutions respond to ions in a nernstian fashion, but they are not ion selective.

The Thermal Decomposition and Hydrolysis of Calcium Carbamoyl Phosphate

Abstract Calcium carbamoyl phosphate (1) was prepared by adding an aqueous calcium chloride solution to a reaction solution of KH2PO4 with KOCN. 1 was unstable at room temprature. 1 was dehydrated to make anhydrous salt and thermally decomposed to liberate ammonia, cyanic acid, and carbon dioxide, finally resulting in the formation of calcium pyrophosphate in air. The apparent activation energies for the three endothermic peaks of the DTA curve were estimated to be 50.0, 83.9, and 148.3 kJ mol−1 respectively. The hydrolysis of 1 in an aqueous solution apparently obeyed the first-order kinetics. The activation parameters for the hydrolysis of 1 were evaluated by using the 31P NMR spectra of 1 with the lapse of the reaction time. The activation energy was 92.2 kJ mol−1; the activation enthalpy, 89.7 kJ mol−1, and the activation entropy, −6.3 e.u.

Thermodynamic studies of transfer of some amino acids and peptides from water to aqueous glucose and sucrose solutions at 298.15 K

Partial molar heat capacities and volumes for a homologous series of amino acids and dipeptides have been measured in aqueous 1 mol kg–1 glucose and sucrose solutions at 298.15 K using flow microcalorimetry and densimetry, respectively. These data have been utilized, in conjunction with the data obtained for them in water earlier, to deduce the partial molar heat capacities and volumes of transfer from water to 1 mol kg–1 aqueous glucose and sucrose solutions. A comparison of these transfer parameters with similar ones in aqueous sodium chloride and calcium chloride solutions is made. The results are explained using the cosphere overlap model and the factors governing the stability of proteins in these sugar solutions have been discussed.

Effect of calcium chloride on the conformation of proteins. Thermodynamic studies of some model compounds.

Partial molar heat capacities (CP2 degrees) and volumes (V2 degrees) for some amino acids and peptides were measured in 1 M aqueous calcium chloride solutions at 298.15 degrees K using a Picker flow microcalorimeter and an oscillating-tube digital density meter. Using the data for these amino acids and peptides in water, the corresponding partial molar heat capacities of transfer (CP2,tr degree) and volumes (V2,tr degree) from water to 1 M aqueous calcium chloride were deduced. These thermodynamic parameters are significantly positive, indicating that strong interactions occur between the ions of calcium chloride and the charged centres of these amino acids and peptides. A comparison has been made with a similar transfer of these compounds to sodium chloride solutions. The thermodynamic parameters of the transfer of peptide group (-CONH) are much more positive in calcium chloride than in sodium chloride solutions. The implication of this result for the ability of calcium chloride to act as a stronger destabilizer of protein conformation is discussed.

Subsurface dissolution and precipitation during leaching of porous ionic solids

Coupled diffusion equations are used to describe the dissolution of porous ionic solids in acidic solutions. The analysis shows that subsurface dissolution can occur when calcium hydroxide is attacked by dilute aqueous solutions of hydrochloric acid; because highly mobile OH− diffuses out of the pore solutions more rapidly than Ca2+ diffuses in, some solid dissolves to keep the subsurface pore solution saturated with calcium hydroxide. With concentrated acid solutions, precipitation can occur just below the solid's surface due to the large influx of Ca2+ leached from the surface. The predictions are verified qualitatively by leaching gel-stabilized suspensions of calcium hydroxide. It is shown that coupled ionic diffusion in saturated pore solutions can produce subsurface dissolution or precipitation without chemical reaction when, for example, calcium hydroxide dissolves in aqueous calcium chloride solutions.

Stress cracking of nylon polymers in aqueous salt solutions

A previous investigation (J. Mater. Sci.22 (1987) 1707) has shown that nylon polymers are susceptible to stress cracking by aqueous calcium chloride at slightly elevated temperatures (50° C). In the present study, the nylon-salt interactions were investigated using thin films of both nylon 6 and nylon 6,6. Chemical, thermal, infrared and dynamic mechanical analyses were performed along with tensile property determinations. Weight gain measurements indicated that above 50° C large increases in sorption occurred for films immersed in either aqueous calcium, lithium, or magnesium chlorides. Both salt ions and water were absorbed at the elevated temperature. In contrast to these results, the data for sodium chloride indicated that only water was absorbed at all temperatures. The sorption process was shown to be physically reversible since the absorbed salt could be removed by immersion in pure water. Moreover the sorption of the salt solution at 100° C did not produce chemical degradation or significant crystallization of the nylons. At higher temperatures the absorbed salt did modify the recrystallization behaviour and increase theTg of the nylons. Significant reductions in tensile modulus were observed for nylon films equilibrated in the salt solutions and tensile elongations at rupture were increased. The effect of increasing temperature and salt type on the sorption process parallels the previously observed stress-cracking activity of the aqueous salt solutions. It is therefore suggested that a plasticization-like mechanism is responsible for the salt-induced crazing of the crystalline nylons.

Stress cracking of nylon polymers in aqueous salt solutions

The susceptibility of nylon polymers to environmental stress cracking in aqueous salt solution was investigated. The time to fail (complete rupture) was recorded for razor-cut precracked samples which were totally immersed in water, sodium chloride, or calcium chloride at various initial stress intensity levels and temperatures. Ductile failures were observed in both water and aqueous sodium chloride at all temperatures. However, in saturated aqueous calcium chloride the nylon failure mode changed from ductile tearing, at room temperature, to crazing and cracking at elevated temperatures (50 to 100 ° C). Lithium and magnesium chlorides were also observed to be potent cracking agents at the elevated temperatures. The temperature interval over which cracking occurred corresponded to the onset of the glass transition temperature, Tg, of the nylon. Thus, nylon 6, having a lower Tg, was more susceptible to cracking than nylon 6,6 at any given temperature. On the other hand, nylon 11, having a lower ratio of amide to methylene groups, was not susceptible to salt-induced cracking. For the nylon 6 and nylon 6,6, the failure kinetics in salt solutions were similar, regardless of whether dry samples or previously moisturized samples were examined. Thus a simple temperature-moisture content equivalence does not apply for salt-induced stress cracking in aqueous solutions.

Densities and apparent molal volumes of aqueous concentrated calcium chloride solutions from 50 to 200�C at 20.27 bar

Densities of aqueous calcium chloride solutions are reported for molalities up to 6.4 mol-kg−1 at temperatures from 50 to 200°C and at 20.27 bar. Apparent molar volumes calculated from experimental densities were fitted to the equations of Rogers and Pitzer, and the temperature dependence of the Pitzer parameters were obtained. The standard deviation of fit for the apparent molar volumes is 0.21 cm3-mol−1 from 50 to 200°C at 20.27 bar.

Calculation of Heat and Mass Transfer Coefficients in a Packed Tower Operating With a Desiccant-Air Contact System

Packed towers can be used for solar regeneration of aqueous solutions and dehumidification of air using aqueous solutions. These processes involve simultaneous heat and mass transfer with heat effects. In order to design a packed tower for aqueous solution-air contacting operations, heat and mass transfer coefficients for each phase are required. For the present study, aqueous calcium chloride solution is used; ceramic Raschig rings and Berl saddles are used as the packing material. In this paper air phase transfer coefficients are correlated with flow rates of air and liquid and the temperature of air, whereas liquid phase coefficients are correlated with rates of air and liquid flow, and the temperature and concentration of the liquid.

Osmotic coefficients of aqueous calcium chloride solutions from 3 to 12 m at 50.degree.C

Osmotic coefficients of aqueous calcium chloride solutions from 3 to 12 m at 50.degree.C

Carbohydrates of the antarctic brown seaweed Ascoseira mirabilis

Mannitol, sucrose and four monosaccharides were obtained from an ethanolic extract of Ascoseira mirabilis. Sequential extraction with aqueous calcium chloride, dilute acid and dilute alkali gave mixtures of laminaran, ‘fucan’ and alginic acid. Laminarans fractionated from the extracts contained different proportions of uniformly (1 → 3) and (1 → 6) linked chains of β- D-glucose residues. The ‘fucan’ contained varying proportions of fucose, galactose and glucuronic acid, small amounts of xylose, mannose, glucose, half ester sulphate and protein. Extraction of the weed under mild alkaline conditions gave a yield of 13.4% of low molecular weight calcium alginate with a mannuronate to guluronate ratio of 30:70 and only a small proportion of sequences of alternating residues. Selective extraction and fractionation gave alginate fractions rich (> 80%) in mannuronate or guluronate.

Osmotic coefficients of aqueous lithium chloride and calcium chloride from their isopiestic ratio to sodium chloride at 50.degree.C

Osmotic coefficients of aqueous lithium chloride and calcium chloride from their isopiestic ratio to sodium chloride at 50.degree.C

Chemical Treatment and Process Modification for Producing Improved Quick‐Cooking Rice

ABSTRACTQuick‐cooking rice was produced by soaking raw, white, long grain rice in a 1% aqueous sodium citrate and calcium chloride solution (50:50) at 50°C for 15 min. The soaked sample was cooked in an autoclave at 121°C for 3 min and freeze‐dried to 20% moisture followed by convective air‐drying to a final moisture of 12%. Nutrient analysis of the rice chemically treated and dried by a combination of both methods contained maximum amounts of thiamin (2.0 μg/g), niacin (27.4 μg/g), and iron (25.1 μg/g). The rehydrated sample, prepared by boiling the rice in water at 100°C for 5 min, received high sensory scores.

ChemInform Abstract: THE SYNTHESIS AND THERMAL DECOMPOSITION OF CALCIUM PHOSPHORAMIDATE

AbstractCaPO3NH2‐H2O wird durch Umsetzen von wäßriger CaClz‐Lösung mit einer Lösung von Kaliumhydrogenphosphoramidat bei pH 9.0‐9.5 unterhalb 5°C dargestellt.

Molecular dynamics and x-ray investigation of an aqueous calcium chloride solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular dynamics and x-ray investigation of an aqueous calcium chloride solutionM. M. Probst, T. Radnai, K. Heinzinger, P. Bopp, and B. M. RodeCite this: J. Phys. Chem. 1985, 89, 5, 753–759Publication Date (Print):February 1, 1985Publication History Published online1 May 2002Published inissue 1 February 1985https://doi.org/10.1021/j100251a007RIGHTS & PERMISSIONSArticle Views521Altmetric-Citations149LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (824 KB) Get e-Alerts

Enthalpies of dilution of aqueous calcium chloride to low molalities at high temperatures

The enthalpy of dilution of CaCl/sub 2/(aq) is obtained to a minimum molality of 1.7 x 10/sup -3/ mol x kg/sup -1/ at temperatures to 673 K from heat and liquid flow microcalorimetry. The measured dilution enthalpies at low concentrations above 573 K are more exothermic than those calculated from the limiting law. Comparison with similar results for NaCl(aq) indicates that extrapolation to infinite dilution based on strong electrolyte models for thermodynamic quantities may lead to significant error at high temperatures.

Thermodynamics of concentrated electrolyte mixtures. 5. A review of the thermodynamic properties of aqueous calcium chloride in the temperature range 273.15-373.15 K

Thermodynamics of concentrated electrolyte mixtures. 5. A review of the thermodynamic properties of aqueous calcium chloride in the temperature range 273.15-373.15 K

The Synthesis and Thermal Decomposition of Calcium Phosphoramidate

Abstract Calcium phosphoramidate monohydrate was made by adding an aqueous calcium chloride solution to an aqueous potassium hydrogenphosphoramidate solution at pH 9.0–9.5 below 5 °C. The product was stable at room temperature, but it was decomposed by heating. When the product was heated at 150 °C in air, the phosphoramidate decomposed to produce anhydrous calcium phosphoramide and also ortho- and diphosphates. The elimination of ammonia from amino groups to form a P–N(H)–P linkage was not observed at this temperature. The phosphoramidate decomposed in air to form ortho-, imidodi-, di-, and a small amount of higher polyphosphates at a temperature higher than 150 °C. Imidodiphosphate was decomposed to diphosphate by moisture in air. β-Calcium diphosphate was formed by heating the phosphoramidate at a temperature higher than 750 °C in air. When the phosphoramidate was heated in dried N2, it showed the same thermal reaction as that in air below 250 °C, while the amount of imidodiphosphate in the thermal product was larger than that in air at a temperature higher than 400 °C.

Effect of structural separation between phosphate and ammonium groups of phospholipid on calcium binding properties as studied by pressure-area analysis of the monolayer

The surface pressure-molecular area relationships of phospholipid monolayers were measured on aqueous substrate with and without dissolved calcium chloride for dipalmitoylphosphatidylalkanolamine homologs each differing in number of methylenes between phosphate and ammonium groups. They are dipalmitoylphosphatidylethanolamine (C16PEt), -propanolamine (C16PPr), -butanolamine (C16PBu), and -pentanolamine (C16PPe). The expansion of the monolayer was observed when it was spread on an aqueous calcium chloride solution of 50.0 m M from which the binding of calcium ions to the polar head group of phospholipid is expected. The degree of expansion was found to be appreciably high for C16PPr, lower for C16PEt and C16PBu, and lowest for C16PPe. The difference was explained by the intramolecular interaction between phosphate and ammonium groups of phospholipid, associated with previous H NMR findings for the same lipid homologs that hydrogen bonding between phosphate and ammonium groups is most weak for C16PPr and strong for C16PEt and C16PPe. The results seem to imply the significance of a particular chemical structure of natural phospholipid in giving the biomembrane moderate affinity to calcium ions.

Asymmetric reduction of steroidal 20-ketones: Chemical synthesis of corticosteroid derivatives containing and 20α, 21-diol and 17α, 20α, 21-triol side chains

A method is presented for the chemical synthesis of corticosteroid derivatives containing the 20α, 21-diol and 17α, 20α, 21-triol side chains. The ketol side chains of cortisol, corticosterone, 11-deoxycortisol, and 11-deoxycorticosterone were reduced at C-20 with sodium borohydride in a two-phase system consisting of aqueous calcium chloride and an organic phase of chloroform or ethyl acetate. Stereoselectivity of reduction was 92% α-oriented for cortisol and 79% α-oriented for 11-deoxycortisol at −27°. The 20α-form diminished relative to the 20β-form with increasing temperature. For the 17-deoxy steroids, reduction to the 20α-form was 23% for 11-deoxycorticosterone and 41% for corticosterone. The 20α 20β ratios of 17-deoxy steroids were unchanged between 0° and −27°. Calcium ions increased the solubility of corticosteroids in the aqueous phase. We propose that calcium ions affect the stereochemistry of reduction by forming a bidentate complex with the side chains of 17α-hydroxy steroids, fixing them in an orientation favorable to 20α-reduction, and by altering the phase partition of the steroids.