Calcium Halides Research Articles

Thermodynamic quantities of surface formation of aqueous electrolyte solutions X. Aqueous solution of 2:1 valence-type salts

The behaviors of a series of calcium halides and of alkali earth metal chlorides in the air/water surface region were studied in comparison with those of alkali metal halides by measuring the surface tension increments of solutions. The effect of salts with divalent cations on the surface tension increments is more pronounced than that of uni-univalent salts, but there are some similarities between these two types. It seems that the anions cause a marked effect on surface tension which is proportional to the magnitude of hydration in the bulk water. We also observed a decrease in the entropy change of surface formation with increasing concentration. The importance of an electrical double layer at the surface is discussed in relation to these surface tension increments.

Effect of replacing calcium oxide with calcium halide on crystallization and some physical properties of calcium vanadium phosphate glass ceramics

The effect of halide ions on density, electrical, magnetic and crystallization kinetics for (20X–50P 2O 5–30V 2O 5) mole% has been investigated, where X=CaO, CaF 2, CaCl 2 and CaBr 2. Halide ions reduce the glass transition temperature, crystallization temperature and activation energy of crystallization. Density, electrical conductivity and magnetic susceptibility increase while molar volume, glass thermal stability and interatomic distance between transition metal ions decrease as the halide ions replace the oxygen ions in these glasses.

Direct synthesis of ortho-dihalogenated arylpyrimidines using calcium halides as halogen sources

Pyrimidines and their derivatives have been used as important motifs in materials and medicinal chemistry. In this Letter, a wide variety of ortho-dihalogenated arylpyrimidines were synthesized with high yields and functional-group tolerance using calcium halides as crucial halogenating agents and cupric trifluoroacetate as oxidant in the presence of air. The generated dichlorinated products could be further manipulated by stepwise Suzuki–Miyaura reaction to afford a wide range of ortho-functionalized arylpyrimidines amenable to physical and biological evaluations.

Palladium‐Catalyzed Monoselective Halogenation of CH Bonds: Efficient Access to Halogenated Arylpyrimidines using Calcium Halides

AbstractA wide variety of ortho‐halogenated arylpyrimidines were prepared with high monoselectivity and functional‐group tolerance by using calcium halides as crucial halogenating agents and cupric trifluoroacetate as oxidant in the presence of air.

Aryl Calcium Compounds: Syntheses, Structures, Physical Properties, and Chemical Behavior

Organocalcium chemistry is still in its infancy. The direct synthesis of activated calcium and (substituted) iodobenzenes allows for the large-scale and high-yield synthesis of aryl calcium iodides. The influence of the substitution patterns of the phenyl group, halogen atom, and solvent is discussed. Aryl calcium iodides show a Schlenk equilibrium that enables the isolation of diaryl calcium derivatives. Owing to the high reactivity of aryl calcium halides, low temperatures have to be maintained throughout the preparative procedures in order to avoid side reactions. A decrease of reactivity and, hence, an enhanced stability at higher temperatures can be achieved by shielding of the calcium atom by increasing the coordination number of the metal center or by substitution of the iodide anion by bulky groups.

Ion-exchange characteristics of 12CaO·7Al 2O 3 for halide and hydroxyl ions

Substitution characteristics of the halide ions F − Cl − for the OH − ions in the crystal lattice of 12CaO·7Al 2O 3 solid solution were investigated. Single phases of composition 11CaO·7Al 2O 3·CaF 2 and 11CaO·7Al 2O 3·CaCl 2 were formed at 900 °C or above. The OH − ions in 12CaO·7Al 2O 3 solid solution, i.e. 11CaO·7Al 2O 3·Ca(OH) 2, could be replaced wholly or partially by F − or Cl − ions from the corresponding calcium halide, forming 11CaO·7Al 2O 3·Ca(OH,F) 2 and 11CaO·7Al 2O 3·Ca(OH,Cl) 2 solid solutions above 500 °C and above 700 °C, respectively. Lattice constants of 12CaO·7Al 2O 3 solid solution changed continuously with the proportion of F − ions or Cl − ions. The F − ions in 11CaO·7Al 2O 3·CaF 2 could be wholly or partially substituted by Cl − ions from CaCl 2 at 900 °C or more, forming the solid solution 11CaO·7Al 2O 3·Ca(F,Cl) 2. The Cl − ions in 11CaO·7Al 2O 3·CaCl 2 could be partially replaced F − ions from CaF 2 at 1000 °C or above, apparently due to slow chloride loss by evaporation.

Effect of Various Halide Salts on the Incompatibility of Cyanocobalamin and Ascorbic Acid in Aqueous Solution

Combination of cyanocobalamin (VB12) and ascorbic acid (VC) has been widely seen in pharmaceutical products and dietary supplements. However, VB12 has been reported that its behavior in stability in aqueous solution is quite different when VC is mixed. In the present study, we examined the stabilities of these vitamins in acetate buffer (pH 4.8) using high performance liquid chromatography. Degradation of VB12 was not observed in the absence of VC in the buffer. However, when VC was mixed in the VB12 solution, VB12 concentrations decreased in accordance with VC degradation. VB12 and VC degradations were inhibited by adding sodium halides to acetate buffer at pH 4.8. These stabilization effects were also observed in the range from pH 3.5 to 5.3 and by adding potassium, magnesium, and calcium halides. Furthermore, our data demonstrated that increases in the halide anion concentrations and atomic number (Cl-<Br-<I-) were proportionally associated with better stabilities of both VB12 and VC. Therefore, choosing an appropriate condition with a certain halide salt may be useful for stabilizing pharmaceutical products and dietary supplements when VB12 and VC are combined in solution.

Coordination of Pyridine N-Oxides with Alkali and Alkaline-Earth Metal Cations in Aqueous Solution

Complexation of pyrdine N-oxides with lithium, sodium, potassium, magnesium, and calcium halides in aqueous solution was studied. The complexes are unstable (K < 0.6 l mol−1) and exist in solution in an equilibrium with their components. The stability of the complexes was studied in relation to the kind of the cation and anion and to the properties of substituents in the N-oxides.

X-Ray diffraction investigations of concentrated aqueous solutions of calcium halides

Concentrated aqueous solutions of calcium chloride and calcium bromide have been investigated by X-ray diffraction. In the diffraction patterns of aqueous chloride solutions of different concentrations, a maximum of intensity is observed in the region 0.6–1.1 Å −1 , while in the investigated aqueous bromide solution no maximum is observed in that region. This pre-peak suggests the existence of positional correlations in solution beyond direct contact. The interpretation is similar to the one proposed by the authors in previous investigations, and is supported by the calculations based on ad hoc molecular models. The influence of the anion is discussed.

X-Ray diffraction investigations of concentrated aqueous solutions of calcium halides

Concentrated aqueous solutions of calcium chloride and calcium bromide have been investigated by X-ray diffraction. In the diffraction patterns of aqueous chloride solutions of different concentrations, a maximum of intensity is observed in the region 0.6–1.1 Å −1, while in the investigated aqueous bromide solution no maximum is observed in that region. This pre-peak suggests the existence of positional correlations in solution beyond direct contact. The interpretation is similar to the one proposed by the authors in previous investigations, and is supported by the calculations based on ad hoc molecular models. The influence of the anion is discussed.

Soil thin-layer chromatography of heavy metal cations with surfactant-modified mobile phases: Mutual separation of Zinc(II), Cadmium(II), and Mercury(II)

Thin-layer chromatography of ten metal ions has been performed on pure soil layers; the mobile phases were aqueous organic and inorganic fertilizer solutions, solutions of aqueous inorganic fertilizer mixed with potassium, sodium, or calcium halide, and aqueous anionic sodium dodecyl sulfate (SDS) solutions with added iodides or chlorides of K, Na, or Ca. A novel mobile phase, 1:9 ( v/v ) 0.001 m SDS-NaCl, was identified for rapid separation of mixtures of Zn 2+ , Cd 2+ , and Hg 2+ .The metal cation mobility observed on pure soil layers with these mobile phases was compared with that obtained on organic-matter-free soil layers. A general trend toward increased metal ion mobility on organic matter-free soil layers was observed. Substitution of SDS by a cationic ( N,N,N -cetyl- N -trimethylammonium bromide) or a nonionic (Tx-100 or Brij 35) surfactant in the mobile phase hampered separation of Zn 2+ from Cd 2+ and Hg 2+ . The effect of inorganic additives (sodium molybdate, KSCN) and acids (oxalic, tartaric...

Stereoselective formation of ansa-metallocenes in reactions of radical-anionic salts of acenaphthylene with lanthanide and calcium halides

ansa-Metallocenes (η5:η5-C24H16)M(THF)2 (M = Sm (1), Yb (2), Ca (3)) and (η5:η5-C24H16)MI(THF) (M = Dy (8), Er (9), Tm (10), Lu (11)) were prepared in 50—90% yields by the in situ reactions of two equivalents of potassium acenaphthylenide K+C12H8– with MI2 or MI3, respectively. Complexes 2 and 3 were also obtained by direct reduction of acenaphthylene with ytterbium and calcium naphthalenides, respectively. An ESR signal of the acenaphthylene radical anion, which was observed upon dissolution of compound 2 in THF, indicates that the [C24H16]2–ansa-ligand dissociated into two [C12H8]·– radical anions. Hydrolysis of complex 2 in benzene afforded 1,1",3,3"-tetrahydro-3,3"-biacenaphthylene (4) and 3,3",4,4"-tetrahydro-3,3"-biacenaphthylene (5). The reaction of complex 2 with ZrCl4 and the reaction of compound 3 with Me3SiCl proceeded with the cleavage of the C—C bond between two acenaphthylene fragments of the [C24H16]2–ansa-ligand to produce (η2-C12H8)ZrCl2(THF)3 (6) and bis(trimethylsilyl)acenaphthene (Me3Si)2C12H8 (7), respectively. Compounds 1—3, 6, 7, and 11 were characterized by 1H and 13C NMR spectroscopy. The temperature dependence of the 1H NMR spectrum of compound 11 in tetrahydrofuran is indicative of the dynamic exchange of the solvent molecules in the coordination sphere of the Lu atom. After cooling of the solution to 210 K, the dynamic process was terminated as evidenced by the nonequivalence of the 1H signals of two acenaphthylene fragments. According to the X-ray diffraction data for complex 11, dimerization of two acenaphthylene radical anions at the Lu atom gave rise to the rac-ansa-metallocene structure. In compound 11, the Lu atom is η5-coordinated by two five-membered rings of the acenaphthylene ligands and also by the I atom and the THF molecule. The coordination environment about the Lu atom is a distorted tetrahedron. The average distance between the lutetium atom and the carbon atoms of the five-membered rings is 2.623 A.

Hydration of the calcium ion. An EXAFS, large-angle x-ray scattering, and molecular dynamics simulation study.

The structure of the hydrated calcium(II) ion in aqueous solution has been studied by means of extended X-ray absorption fine structure spectroscopy (EXAFS), large-angle X-ray scattering (LAXS), and molecular dynamics (MD) methods. The EXAFS data displayed a broad and asymmetric distribution of the Ca-O bond distances with the centroid at 2.46(2) A. LAXS studies on four aqueous calcium halide solutions (1.5-2 mol dm(-)(3)) gave a mean Ca-O bond distance of 2.46(1) A. This is consistent with a hydration number of 8 determined from correlations between mean distances and coordination numbers from crystal structures. The LAXS studies showed a second coordination sphere with a mean Ca.O(II) distance of 4.58(5) A, and for the hydrated halide ions the distances Cl.O 3.25(1) A, Br.O 3.36(1) A, and I.O 3.61(1) A were obtained. Molecular dynamics simulations of CaCl(2)(aq) were performed using three different Ca(2+)-OH(2) pair potentials. The potential from the GROMOS program gave results in agreement with experiments, i.e., a coordination number of 8 and an average Ca-O distance of 2.46 A, and was used for further comparisons. Theoretical EXAFS oscillations were computed for individual MD snapshots and showed very large variations, though the simulated average spectrum from 2000 snapshots gave satisfactory agreement with the experimental EXAFS spectra. The effect of thermal motions of the coordinated atoms is inherent in the MD simulation method. Thermal disorder parameters evaluated from simulated spatial atom distribution functions of the oxygen atoms coordinated to the calcium ion were in close agreement with those from the current LAXS and EXAFS analyses. The combined results are consistent with a root-mean-square displacement from the mean Ca-O distance of 0.09(2) A in aqueous solution at 300 K.

Calcium targets with low hydrogen content

The hydrogen content of calcium targets was determined by elastic recoil detection (ERD). Thereby a Q3D magnetic spectrograph was used to obtain best depth resolution of the hydrogen profiles. The two most promising preparation methods for calcium targets with low hydrogen content — deposition of the most stable calcium halide CaF 2 and protecting metallic Ca by a diffusion barrier of Al — have been examined. A detailed description of the technique that resulted in the minimal hydrogen content of the targets will be given.

Thermodynamics of mixing of liquids in the system Ca 3(PO 4) 2CaCl 2CaF 2Ca(OH) 2

Molten calcium halide and hydroxide salts may be used as flux and reactants in determining apatite exchange equilibria and solid solution behavior. New experimental data and published phase equilibria are used to determine a thermodynamic model of melts and solids along the binary joins of the anhydrous apatite system Ca 3(PO 4) 2CaCl 2CaF 2Ca(OH) 2. In this model, melt components are expressed as Ca 0.5 X, where X is hydroxide or a halogen, or as Ca 1.5PO 4. The derived binary interaction parameters ( W G ' s) are sufficient to describe deviations from Raoultian behavior for the data. Standard state data are derived for molten Ca(OH) 2 and Ca 3(PO 4) 2, and for the intermediate compounds CaClF, CaClOH, and Ca 2PO 4Cl. Melts in the CaCl 2CaF 2 system show ideal mixing behavior, while the calcium hydroxide-bearing molten salts form asymmetric regular solutions. The hydroxide-bearing melts show the small positive enthalpies of mixing typical for mixed-anion salts. Similar behavior is measured in simpler molten salt mixtures. The positive deviations from Raoultian behavior are not a mathematical artifact of the model. Data are less extensive for the salt-phosphate systems but cover the essential portions of the systems where salt to phosphate ratios are high. The mixtures of the molten salts and phosphates salts show large negative enthalpy interaction parameters ( W H ), as is expected in eutectic systems which mix a high-melting-point crystal with a low-melting-point flux. Adequate reproduction of the data requires that some entropy interaction parameters be negative, although small. This implies the presence of ordering in the melt, which is manifested in more polymerized phosphate liquids and glasses as halogenated and hydroxylated orthophosphate and pyrophosphate species. Results of the model indicate that the quaternary system is a good choice for determination of activity-composition relations for the apatites. Comparison of common sources of standard state thermodynamic data ( Robie et al., 1979; JANAF, Chase et al., 1985; CODATA, Garvin et al., 1987) shows that the data for the salts are very similar where they are not identical. At temperatures below 900°C in the ternary systems, liquid compositions will be on or near the apatite-crystalline salt cotectics, and dissolve less than 1 mol% Ca 3(PO 4) 2. This makes CaCl 2CaF 2 mixtures excellent candidates for determination of unambiguous apatite activity-compositional relations. Only the Ca(OH) 2 liquidus is strongly affected by the addition of phosphate, but this effect is closely described by a regular solution model.

Kinetic, Solution, and Interfacial Aspects of Iron Corrosion in Heavy Brine Solutions

Abstract The corrosion rates of iron at temperatures between 60 and 120°C have been determined in very concentrated zinc halide solutions. The effects of calcium halide were investigated. The corro...

Immersion treatment of sinter into calcium halide solution.

The influences of the immersion of sinter into calcium halide aqueous solutions or suspensions and the subsequent drying of sinter on the reduction degradation index (RDI) and relative reducibility index (RI) were investigated.The immersion treatments of sinters were carried out at a room temperature in air and in vacuum. The calcium halide concentration of aqueous solution or suspension was changed from 1.0 to 10.0 wt%.When sinter was immersed into CaCl2 and CaBr2 aqueous solutions, RI remained at the same value of the original sinter, while the value of RDI decreased, in other words, the degradation during reduction was improved, particularly in case of CaBr2.On the other hand, when sinter was immersed into CaF2 suspension, the effect of the immersion treatment on RI and RDI was scarcely detected.

Two monomeric, octahedral complexes of alkaline earth metal salts: syntheses, physical characteristics, and crystal structures of Srl2·4HMPA and Sr(NCS)2·4HMPA [HMPA = O : P(NMe2)3

The complexes (Srl2·4HMPA)n, (1), and [Sr(NCS)2·4HMPA]n, (2), [HMPA = O : P(NMe2)3], were synthesised by reactions of Sr metal, NH4X solids (X = I and SCN, respectively), and HMPA (1:2:4 molar amounts) in toluene, and several HMPA complexes of calcium and barium halide and thiocyanate salts have been made by analogous routes; X-ray diffraction has shown that both Sr species have discrete molecular (n=1), octahedral structures, the X groups being trans in (1) but cis in (2).

Sugar interaction with calcium ion. synthesis and vibrational spectra of crystalline β-d-fructose and its calcium halide adducts

D-fructose reacts with the calcium ion to give complexes of the type Ca(δ- d-fructose)Cl 2-2H 2O, Ca(⨿- D-fructose) 2 Cl 2·3H 2O and Ca(⨿- d-fructose)Br 2-2H 2O. The infrared spectra of the free⨿- d-fructose and its calcium compounds are examined and a correlation between the spectral changes and the coordination sites involved has been established. Structurally known Ca(⨿- d-fructose)Cl 2· 2H 2O and its isomorphous Ca(⨿- d-fructose)Br 2·2H 2O showed that each calcium ion is seven-coordinated, binding to three symmetry related fructose molecules through O(2), O(3) of the first, O(4), O(5) of the second, and O(1) of the third molecule as well as to two water molecules, whereas in the Ca(⨿- d-fructose) 2Cl 2 · 3H 2O compound the calcium cation is eight coordinated, binding to two sugar molecules via O(1), O(4), and O(5) of each sugar moiety, as well as to two water molecules. Spectroscopic evidence presented here indicated that the two structurally dissimilar 1:1 and 2:1 calcium chloride adducts are spectrally different, while the 1:1 calcium chloride and the bromide complexes have virtually identical infrared spectra. The rearrangement of the strong hydrogen bonding network of the free sugar occurred upon metalation. Furthermore, the band assignments in the OH stretching region have been correlated with the sugar intermolecular hydrogen-bonding O  O distances reported from the x-ray and the neutron diffraction measurements.

Reactivity of Fluorochloromethanes with Desert Sands

AbstractDesert sand reactivity with halocarbons like CCl3F (F11), CCl2F2 (F12) and CHCl2F (F21) has been proved. Reactivity increases in the sense: F12 ⩽ F21 &lt; F11 and is favoured by temperature and short activation of samples at 673 K. For F11, the main reaction products are CCl4 and COCl2, but some transformation to F12 has been observed too. An influence of the desert sand origin (i.e. of its phase composition) has been also found. — X‐ray photoelectron spectra of samples after reaction show the presence of F and Cl on their surface, mainly as calcium halides, and in direct proportionality with reactivity.