Behavior of manganese(II) in calcium formate solutions

The solubility in the system Ca(HCOO)₂-Mn(HCOO)₂-H₂O at 25°C was studied by the isothermal method. The behavior of manganese in Ca(HCOO)₂ crystallization from aqueous solutions was examined with ⁵⁴Mn tracer in the concentration range 10^?3–10^?5 wt %.     

A theoretical study of malonate and formate calcium binding by ab initio techniques

Ab initio calculations at the STO—3G level have been performed on the binding of CA(II) ion to malonate and formate with and without d orbitals in the basis set for the CA(II) ion. The malonate and formate binding results with CA(II) are similar. The addition of d orbitals to CA(II) has little effect on the conformational minimum. The results are qualitatively similar to those from our previous calculations on the Mg²⁺—malonate interaction: a single carboxyl interaction with the metal ion appears to be preferred over a conformation in which two carboxyl groups bind to Ca(II). Moreover, the single carboxyl group interaction with CA(II) appears to be favored over the binding of CA(II) to a single oxygen of a carboxyl group.     

Preparation of calcium cyclopentadienyl complexes using calcium borohydride

Calcium borohydride reacts with sodium cyclopentadienyl compounds in tetrahydrofuran solution to give the corresponding calcium cyclopentadienyl complexes. The reaction proceeds easily and gives high yields.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 377–378, February, 1993.     

An ab initio mo study of calcium and magnesium complexes with malonate and formate

Quantum mechanical SCF calculations were performed on magnesium and calcium complexes of malonate and malonate/formate coordination. The calcium malonate structure is in substantial agreement with recent X-ray results on -ethylmalonate. The magnesium complexes are generally more tightly bound than calcium, although qualitatively, the calcium and magnesium structures are similar. Experimental binding results for divalent ions with malonates and EDTA are discussed in view of the current calculations.     

Purification assay to prepared ultrapure carboxymethyl-chitosan

Carboxymethyl Chitosan (CMCh) is a semi-synthetic derivative of chitosan (a natural biopolymer) with increasing biomedical applications as a matrix or scaffold material for tissue engineering applications. Since, the presence of impurities can cause immunological reactions in vivo where ultimately pure materials are needed. To this end, purity of commercial-grade CMCh samples was investigated here along with their purification by a solvent/nonsolvent technique. The resulting polymer was characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX) to confirm the validity of the purification process.     

Electron spin resonance of γ-iradiated single crystals of calcium formate

The electron spin resonance spectra of CO₂⁻ in an irradiated single crystal of calcium formate have been recorded. The ¹³C hyperfine splitting tensor has been measured and the orientation of the CO₂⁻ molecule with respect to the crystallographic axes is compared with that of the undamaged HCO₂⁻ molecules. The results show that there is a reorientation of the CO₂ group when the CH bond is broken.     

Efficient production of ultrapure manganese oxides via electrodeposition

A new process for the production of electrolytic amorphous nanomanganese oxides (EAMD) with uniform size and morphology is described. EAMD are produced for the first time by cathodic deposition from a basic aqueous solution of potassium permanganate at a constant temperature of 16°C. The synthesized materials are characterized by XRD, SEM, TEM, and HRTEM. The materials produced at 5.0 V at constant temperature are amorphous with homogeneous size and morphology with an average particle size around 20 nm, which appears to be much lesser than the previously reported anodic EAMD. A potentiostatic electrodeposition with much lesser deposition rate (with respect to previously reported anodic depositions) is considered to be the reason behind the very low and homogenous particle size distribution due to the lesser agglomeration of our as-synthesized nanoparticles.     

A theoretical study of the chelation complex comprising formate ions, calcium ion and water of hydration

Ab initio calculations at the STO-3G level have been performed on the binding of Ca(II) ion to two formate ions. Two logical chelation structures have been studied with and without water of solvation. Differential solvation effects are found to be sufficiently large to invert the order of energetically favored structures.     

Atmospheric chemistry of isopropyl formate and tert‐butyl formate

Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH₃)₂, and tert‐butyl formate, HC(O)OC(CH₃)₃. Product distributions are reported from both Cl‐ and OH‐initiated oxidation, and reaction mechanisms are proposed to account for the observed products. The proposed mechanisms include examples of the α‐ester rearrangement reaction, novel isomerization pathways, and chemically activated intermediates. The atmospheric oxidation of isopropyl formate by OH radicals gives the following products (molar yields): acetic formic anhydride (43%), acetone (43%), and HCOOH (15–20%). The OH radical initiated oxidation of tert‐butyl formate gives acetone, formaldehyde, and CO₂ as major products. IR absorption cross sections were derived for two acylperoxy nitrates derived from the title compounds. Rate coefficients are derived for the kinetics of the reactions of isopropyl formate with OH (2.4 ± 0.6) × 10^?12, and with Cl (1.75 ± 0.35) × 10^?11, and for tert‐butyl formate with Cl (1.45 ± 0.30) × 10^?11 cm³ molecule^?1 s^?1. Simple group additivity rules fail to explain the observed distribution of sites of H‐atom abstraction for simple formates. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 479–498, 2010     

Preparation of pure monodisperse calcium carbonate particles

The non-template synthesis of monodisperse spherical particles of calcium carbonate is reported. Particles of a 3.5–4.5 μm size were produced by precipitation of calcium carbonate from alcohol solution at subzero temperatures.     

Preparation and FT-IR spectra of calcium bilirubinate

In this investigation two calcium bilirubinates compounds, Ca(HBR)₂·H₂O and Ca(BR)·2H₂O, were prepared. Their Fourier transform infrared spectra were measured in KBr discs and in fluorolube and nujol mulls, respectively. The results suggest that it is better to identify the Ca(HBR)₂·H₂O and Ca(BR)·2H₂O with fluorolube and/or nujol mulls when examining mixtures (e.g. gallstone).     

Preparation of calcium plumbate via different route

Calcium plumbate Ca₂PbO₄ was prepared by sol–gel methods (Pechini complex route with two varieties and water soluble polymer method) and by solid state reaction. The sol–gel prepared samples contained calcium plumbate as the only one phase as early as after 2 h annealing at 800 °C. Phase composition was detected by XRD measurement and by Raman spectroscopy. The next annealing at 800 °C for 24 h induced weak Pb losses displayed by present CaO (according to phase equilibrium) and confirmed by XRF measurement. The Pb losses were smaller for the sol–gel prepared samples probably due to earlier formation of Ca₂PbO₄. Microstructure and grain size were also established. Sol–gel prepared samples had regularly distributed grains with a small distribution interval with median value in order of 1 μm. Differences in microstructure of solid state and sol–gel samples are presented on SEM micrographs.     

碳酸钙微米球的制备与表征

采用醋酸钙和碳酸钠为原料,在反应温度为5℃和柠檬酸三钠质量百分浓度为15%的条件下,采用沉淀法合成出了粒度为1～4μm、分散性好的球形碳酸钙粉体。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、红外光谱仪(IR)、原子力扫描探针显微镜(ASPM)、光学显微镜、粒度分析仪等对样品进行了表征,并用光学显微镜跟踪考察了碳酸钙微米球的形成过程。结果表明,碳酸钙微米球是由大量纳米级颗粒组装而成。     

Ab initio study of the conformations of chloromethyl formate and fluoromethyl formate

Ab initio calculations are reported for the conformational potential energy surfaces of chloromethyl formate and fluoromethyl formate at minimal basis set level. The halomethyl group is shown to lie Z to the carbonyl group. A plateau on the potential energy surface demonstrates that the halomethyl group can rotate freely. The halogen atom therefore moves from an antiperiplanar (ap) to a synclinal (sp) position with respect to the carbonyl group. The effects on IR spectra and dipole moments are discussed.     

Gram-negative bacteria viable in ultrapure water: identification of bacteria isolated from ultrapure water and effect of temperature on their behavior

This study describes the effect of temperature on the behavior of bacteria viable in ultrapure water and the contamination of ultrapure water by bacteria. Three species of bacteria were isolated from ultrapure water (total organic carbon, 60 ppb and 5 ppb; effluent resistivity > 18 MΩ cm at 25°C) and identified by morphological and physiological characteristics. The three isolates were incubated in water for injection and PYG broth to check the growth profile at various temperatures. In PYG broth, temperature influenced the behavior of bacteria directly; however, it did not in water for injection. By checking both viable and non-viable bacterial numbers and endotoxin concentration in pure water, the water was found to be contaminated with non-viable bacteria and newly generated endotoxins besides viable bacteria. A column treatment, a mixed bed of fully regenerated strong acid cation exchange resin (SACER) and strong base anion exchange resin (SBAER), was used to remove bacteria from pure water. Bacteria could not grow on the surfaces of ion exchange resins in the mixed bed. The removal of bacteria was more effective as pure water was circulated through the mixed bed more rapidly.     

Determination of naturally occurring radionuclides in ultrapure organic liquids

For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10^–16g/g for U and Lu, in the 5 · 10^–15g/g range for Th and Sm, in the 1 · 10^–14g/g region for La, 5 · 10^–13g/g for Rb, Cd and 2 · 10^–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and Zn are presented as well.     

Determination of iron in ultrapure water by atomic absorption spectroscopy

Summary Beside ionic impurities, DI water contains non-ionic compounds, which mainly consist of the oxyhydrates of the elements Fe, Ti, and Si present as colloids. This paper describes an analytical method for Fe, which is based on a simple enrichment by evaporation and the subsequent determination by flameless AAS. It is demonstrated that DI water systems, which are mainly based on coprecipitation and ion exchange, remove the Fe from the main water only to a small extent. The Fe content in DI water shows significant variations.

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Bestimmung von Eisen in hochreinem Wasser durch Atomabsorptionsspektroskopie

Zusammenfassung Neben ionischen Bestandteilen enthält selbst hochreines Wasser auch nicht-ionische Komponenten, hauptsächlich Oxidhydrate der Elemente Ti, Fe und Si, die als Kolloide vorliegen. Die analytische Bestimmung des Eisens durch Eindampfen in einer einfachen Anordnung mit anschließender flammenloser AAS wird beschrieben. Es wird gezeigt, daß DI-Wasseranlagen, die heute zumeist noch nach dem Prinzip der Mitfällung und anschließendem Ionenaustausch arbeiten, nur begrenzt kolloidal vorliegendes Eisen entfernen und daß das Reinstwasser in seinem Fe-Gehalt stärkeren Schwankungen unterworfen ist.

     

Determination of naturally occurring radionuclides in ultrapure organic liquids

For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10^–16g/g for U and Lu, in the 5 · 10^–15g/g range for Th and Sm, in the 1 · 10^–14g/g region for La, 5 · 10^–13g/g for Rb, Cd and 2 · 10^–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and Zn are presented as well. Received: 14 May 1997 / Revised: 28 August 1997 / Accepted: 9 September 1997     

钛酸钙的电沉积法制备及表征

采用硝酸钙为钙源,钛酸丁酯为钛源,通过电极沉淀法制备钛酸钙.利用红外光谱仪对制备所得的钛酸钙进行表征.结果显示,在室温条件下,于外加5 V的电场中反应3 h,所得前驱体在800℃下焙烧2 h可得到纯度较高的钛酸钙产品.