Effect of Concentration of Structurally-Different Carboxylic Acids on Growth and Aggregation of Calcium Oxalate in Gel Systems

The effect of concentration of structurally-different carboxylic acids such as ethylene diamine tetraacetic acid （H4edta）, citric acid （H3cit）, tartaric acid （H2tart）, and acetic acid （HOAc） on growth and aggregation of calcium oxalate （CaOxa） in gel systems was comparatively investigated. H2tart and H3cit could change the morphology of cal- cium oxalate monohydrate （COM） and induce the formation of calcium oxalate dihydrate （COD）. H4edta could induce the formation of COD at a lower concentration of 0.33 mmol/L and have the strongest ability to inhibit aggregation of COM. HOAc inhibited COM aggregation only at a higher concentration than 500 mmol/L. With increasing the number of carboxylic groups in an acid or increasing the concentration of carboxylic acid, the capacity of this acid to induce COD formation and to inhibit growth and aggregation of COM crystals increased. That is, this capacity followed the order： H4edta〉H3cit〉H2tart〉 〉HOAc. The result in this work suggested that the presence of H3cit and H2tart in urine played a role in the natural defense against stone formation.     

Cerimetry in non-aqueous media

Summary It was found that ceric oxalate is an intermediate product in the oxidation of oxalic acid by ammonium hexanitrato cerate in solvents such as acetonitrile, and a mixture of acetonitrile and glacial acetic acid. Conditions for the formation of ceric oxalate and its decomposition into carbon dioxide and cerous oxalate have been studied. An analytical method for the estimation of oxalic acid in non-aqueous media has been evolved based on this reaction.

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Zusammenfassung Es wurde festgestellt, daß bei der Oxydation von Oxalsäure mit Ammoniumhexanitratocerat(IV) in Acetonitril oder einem Gemisch von Acetonitril und Essigsäure Cer(IV)-oxalat als Zwischenprodukt auftritt. Die Bedingungen für die Bildung von Cer(IV)-oxalat und seine Zersetzung zu CO₂ und Cer(III)-oxalat wurden untersucht. Ein Verfahren zur Oxalsäurebestimmung in nichtwäßrigem Medium wurde ausgearbeitet.

     

Solute—solvent interactions: dissolution of sparingly soluble silver salts of dibasic and tribasic inorganic and organic acids in water + acetic acid mixtures

Values for the solubilities of salts Ag₂X (where X is sulphate, chromate, tungstate, dichromate, oxalate, malonate, succinate, glutarate, or adipate) and Ag₃Y (where Y is phosphate, arsenate or ferrioxalate) in four different compositions of water + acetic acid (10, 20, 40 and 60 wt.% acid) have been determined at 25°C. Solubility data are discussed in the light of electrostatic and solute—solvent interaction effects on the dissolution processes of the silver salts.     

Determination of Urinary Oxalate With Disposable Oxalate Oxidase Hembrane Strips

Abstract

We describe in this paper a simple and easy method of entrapping oxalate oxidase and peroxidase in acrylamide membrane and demonstrate the use of such enzyme membrane strips in the rapid determination of urinary oxalate. A crude preparation of 45-60% acetone cut obtained from banana fruit peel (Musa paradisiaca; French plantain) homogenate serves as a source of oxalate oxidase, which decomposes oxalate into CO₂ and H₂O₂. the oxalate content of a given urine sample is determined by introducing a small enzyme membrane strip (1 × 1 cm) into an aliquot of buffered urine containing a suitable chromogen for peroxidase and then measuring the colour developed due to the interaction of peroxidase with the newly formed H₂O₂ and the chromogen. Urine samples are pretreated with sodium nitrite to eliminate the interference of ascorbic acid in the assay. the enzyme membrane assay compares well with that of wet enzyme assay of oxalate in sensitivity and reliability.     

Synthesis,structure, and magnetism of a ytterbium coordination polymer with 5-sulfonyl-1,2,4-benzenetricarboxylate and oxalate

[Yb₂(SBTC)(ox)(H₂O)₅] _n (1) (H₄-SBTC?=?5-sulfonyl-1,2,4-benzenetricarboxylic acid and ox?=?oxalate) has been hydrothermally synthesized by reaction of 5-sulfonyl-1,2,4-benzenetricarboxylic acid with Yb(NO₃)₃?5H₂O. In situ formation of oxalate derived from H₄-SBTC is unprecedented and adds a new oxalate formation reaction to in situ ligand syntheses. Compound 1 features a 2-D bilayered coordination network, which is further extended into a 3-D supramolecular framework through interlayered hydrogen bonds. Magnetic measurements on 1 indicate that there is an antiferromagnetic interaction between Yb(III) ions.     

Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex

The controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular Mn^III‐corrole complex, which is modified on the three meso‐positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO₂. Electrochemical reduction of Mn^III leads to an electroactive Mn^II species, which binds CO₂ and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO₂ to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h^?1, when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the Mn^III‐corrole center.     

Effect of Acids on Crystallization of Lithium Borate Films

Lithium borate films in amorphous and crystalline (Li₂B₄O₇) states were prepared from alkoxide solutions hydrolyzed in the presence or absence of hydrochloric acid or acetic acid. The acids suppressed crystallization of the amorphous films into Li₂B₄O₇, with acetic acid being the stronger suppressor. In order to determine the suppressing mechanism, we investigated the distribution of boron-containing species in the solutions by¹¹B-NMR. Boron in the non-acidified solution existed as both B(OH) ₄ ⁻ and polyborate species, including B₄O₅(OH) ₄ ²⁻ , which is easily transformed into the crystal nucleous of Li₂B₄O₇. In the solutions containing hydrochloric acid or acetic acid, however, boron was present mainly as B(OH)₃ and the formation of the polyborate species was suppressed, leading in turn to the suppression of crystallization into Li₂B₄O₇. X-ray fluorescence analysis showed that acetic acid produced a larger amount of residual carbon in the films than did hydrochloric acid. We concluded that the residual carbon also inhibited crystallization of the films into Li₂B₄O₇.     

Precipitation of plutonium oxalate from homogeneous solutions

A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92–98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(C₂O₄)₂·6H₂O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuO₂ obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen.     

Ag/TiO2光催化还原硝酸氮

利用化学还原法制备不同Ag掺杂量TiO₂纳米催化剂,采用TEM、XRD、XRF和UV-Vis对催化剂进行表征。考察了催化剂在紫外光(254 nm)和可见光照射下还原初始浓度100 mgN·L^-1水相硝酸氮的活性和效果。重点考察了紫外光照射下Ag掺杂量、不同空穴捕获剂(甲酸、甲醇、乙酸、乙醇、草酸、草酸钠等)及甲酸浓度对硝酸氮还原的影响;对硝酸氮转化率和总氮去除率、形成亚硝酸氮、氨氮浓度及氮气选择性的影响。甲酸浓度为0.030 mol·L^-1、Ag掺杂量为1.0wt%时催化剂效果最佳。此时,硝酸氮、总氮的转化率分别为98.43%、78.13%;亚硝酸氮浓度为零,转化的硝酸氮中只有20.76%转化为氨氮,氮气选择性为79.24%。可见光下进行光催化还原反应时,硝酸氮转化率仅37.98%,但氮气的选择性较高。     

Morphological control of calcium oxalate particles in the presence of poly-(styrene-alt-maleic acid)

Calcium oxalate (CaOx) particles exhibiting different shapes and phase structures were fabricated by a simple precipitation reaction of sodium oxalate with calcium chloride in the absence and presence of poly-(styrene-alt-maleic acid) (PSMA) as a crystal modifier at room temperature. The as-obtained products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of reaction conditions including pH, [Ca²⁺]/[C₂O₄²⁻] ratio and concentration of PSMA and CaC₂O₄ on the crystal forms and morphologies of the as-obtained calcium oxalate were investigated. The results show that various crystal morphologies of calcium oxalate, such as parallelograms, plates, spheres, bipyramids etc. can be obtained depending on the experimental conditions. Higher polymer concentration favors formation of the metastable calcium oxalate dihydrate (COD) crystals. Lower pH is beneficial to the formation of plate-like CaOx crystals. Especially, the monodispersed parallelogram-like CaOx crystals can be produced by PSMA as an additive at pH 2. PSMA may act as a good inhibitor for urolithiasis since it induces the formation of COD and reduces the particle size of CaOx. This research may provide new insight into the morphological control of CaOx particles and the prevention of urolithiasis.     

On the separation of cesium and strontium from oxalate filtrate by neutralization

At the treatment of HLLW (high-level liquid radioactive waste) by oxalate precipitation, the filtrate is occured as a waste. But various elements including Cs and Sr are contained in the oxalate filtrate. It is very important, therefore, to separate from each other in a viewpoint of ultimate isolation of heat generating nuclides such as Cs and Sr from HLLW. In this study, the simulated oxalate filtrate, consisted of five elements (Cs, Sr, Ru, Fe and Mo) and organics (oxalic acid and ascorbic acid), was prepared, from which the separation of Cs and Sr was carried out by neutralization with NaOH. As a result, the simulated solution could be divided into Cs, Sr and Ru containing groups with pH. Sr was readily precipitated as forms of Sr(C₂O₄)·nH₂O at pH 3. Iron and ruthenium were also co-precipitated around pH 8, and Cs and Mo remained in the resulting solution.     

One‐Step Reforming of CO2 and CH4 into High‐Value Liquid Chemicals and Fuels at Room Temperature by Plasma‐Driven Catalysis

The conversion of CO₂ with CH₄ into liquid fuels and chemicals in a single‐step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one‐step process from CO₂ and CH₄ at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH₄ and CO₂ is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.     

An unprecedented two-dimensional Eu(III) coordination polymer Eu(OOC–C5H4N–CH2–CH2–COO)(OOC–COO)·2H2O formed by in situ reaction of fumaric acid and isonicotinic acid: Crystal structure and luminescent properties

Hydrothermal reaction of fumaric acid and isonicotinic acid in presence of trace quantity of nitric acid produced an unprecedented two-dimensional coordination polymer Eu(OOC–C₅H₄N–CH₂–CH₂–COO)(OOC–COO)·2H₂O containing in situ formed new ligands, 3-(4-pyridinecarboxylate)propionic acid (inpro) and oxalate (ox) moieties. The formation of inpro ligand from isonicotinic acid and fumaric acid is presumably through dehydration between 3-hydroxylpropionic acid and 4-carboxypyridinium moieties present under the above conditions, and the oxalate formation due to the reductive coupling of CO₂ radicals generated from 2-hydroxysuccinic acid through C–C bond cleavage. The compound crystallizes in monoclinic P2₁/C space group and contains nine-coordinated Eu³⁺ ion having a distorted mono-capped square-antiprismatic geometry. While two chelatively bridging oxalate moieties coordinating through four of their O atoms lead to the formation of zigzag Eu(III)–oxalate chains, four uniquely bridging anionic inpro ligands which coordinate through five O centers altogether make the system take an overall two-dimensional network arrangement. Upon excitation at 359 nm the compound exhibits interesting luminescent properties in solid state with several intense bands in the visible region; the most intense and sharp emission being in the red region at 615 nm due to ⁵D₀ → ⁷F₂ transition, facilitated by the low-symmetry coordination environment around Eu³⁺ ion by the ligands.     

210Pb and210Po in tobacco-with a special focus on estimating the doses of210Po to man

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.     

Synergy of Cu/C3N4 Interface and Cu Nanoparticles Dual Catalytic Regions in Electrolysis of CO to Acetic Acid

Electrochemical reduction reaction of carbon monoxide (CORR) offers a promising way to manufacture acetic acid directly from gaseous CO and water at mild condition. Herein, we discovered that the graphitic carbon nitride (g-C₃N₄) supported Cu nanoparticles (Cu−CN) with the appropriate size showed a high acetate faradaic efficiency of 62.8 % with a partial current density of 188 mA cm⁻² in CORR. In situ experimental and density functional theory calculation studies revealed that the Cu/C₃N₄ interface and metallic Cu surface synergistically promoted CORR into acetic acid. The generation of pivotal intermediate −*CHO is advantage around the Cu/C₃N₄ interface and migrated *CHO facilitates acetic acid generation on metallic Cu surface with promoted *CHO coverage. Moreover, continuous production of acetic acid aqueous solution was achieved in a porous solid electrolyte reactor, indicating the great potential of Cu−CN catalyst in the industrial application.     

Aripiprazole salts. III. Bis(aripiprazolium) oxalate–oxalic acid (1/1)

The asymmetric unit of the title salt [systematic name: bis(4‐(2,3‐dichlorophenyl)‐1‐{4‐[(2‐oxo‐1,2,3,4‐tetrahydroquinolin‐7‐yl)oxy]butyl}piperazin‐1‐ium) oxalate–oxalic acid (1/1)], 2C₂₃H₂₈Cl₂N₃O₂⁺·C₂O₄²⁻·C₂H₂O₄, consists of one protonated aripiprazole unit (HArip⁺), half an oxalate dianion and half an oxalic acid molecule, the latter two lying on inversion centres. The conformation of the HArip⁺ cation differs from that in other reported salts and resembles more the conformation of neutral Arip units in reported polymorphs and solvates. The intermolecular interaction linking HArip⁺ cations is also similar to those in reported Arip compounds crystallizing in the space group P, with head‐to‐head N—H...O hydrogen bonds generating centrosymmetric dimers, which are further organized into planar ribbons parallel to (01). The oxalate anions and oxalic acid molecules form hydrogen‐bonded chains running along [010], which `pierce' the planar ribbons, interacting with them through a number of stronger N—H...O and weaker C—H...O hydrogen bonds, forming a three‐dimensional network.     

Synthesis and Verification of 9,10-Diphenylanthracene and Its Utility as a Fluorescer in a Peroxyoxalate Chemiluminescence System. An Organic Laboratory Project Integrating Synthesis with Fluorescence and Chemiluminescence

A project for the organic laboratory integrating the organic synthesis of 9,10-diphenylanthracene with fluorescence and chemiluminescence is described. The fluorescent compound is synthesized from anthraquinone by reaction with phenyllithium and subsequent hydrolysis and reduction with KI and NaH₂PO₂ in acetic acid. The structure of the product is verified by its melting point and by IR, ¹H NMR, and fluorescence spectroscopy. A peroxyoxalate chemiluminescent reaction using bis(2-butoxycarbonyl-3,4,6-trichlorophenyl) oxalate and hydrogen peroxide as the energy source is tested. The chemiluminescence emittance spectrum of the prepared diphenylanthracene is found to be essentially identical to that of the fluorescence spectrum of the same compound. Finally, the kinetics of the chemiluminescent reactions using different intensity-modifiers are monitored by measuring intensity-versus-time decay curves.     

Lanthanoidkomplexe von 1‐(2‐Propenyl)‐ und 1‐(3‐Butenyl)‐1,4,7,10‐tetraazacyclododecan‐4,7,10‐triessigsäure

η³‐1,4,7,10‐tetraazacyclododecane molybdenum tricarbonyl reacts with allyl bromide and 3‐butenyl bromide in dimethylformamide in the presence of K₂CO₃ yielding 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane ( 1a ) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane ( 1b ), which on their part react with bromoacetic acid tert‐butyl ester in CH₃CN to give 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid tert‐butyl ester ( 2a ) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid tert‐butyl ester ( 2b ), respectively. Compounds 2a and 2b are converted into the corresponding acids 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid ( 4a ) (MPC) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid ( 4b ) (MBC) via the trifluoroacetates 3a and 3b . Sm(NO₃)₃(H₂O)₆, LuCl₃(THF)₃, and TmCl₃(H₂O)₆ react with 4a and 4b forming the lanthanide complexes Sm(MPC) ( 5 ), Lu(MPC) ( 6 ), Tm(MPC) ( 7a ) and Tm(MBC) ( 7b ). The IR as well as the ¹H and ¹³C NMR spectra of the new compounds are reported and discussed.     

Speciation of tin in sediments and soils by leaching

For the evaluation of the speciation of Sn in solid samples, a leaching sequence is presented, which takes into account the special properties of the element investigated. The sample is leached with ethanol (organics), 25% acetic acid (carbonates), oxalate (coprecipitation upon Fe/Mn-hydroxides), then oxidized with KMnO₄ (sulfides), and finally sublimed with NH₄I (cassiterite); the silicate fraction is found as the difference to the total decomposition value (e.g. LiBO₂).Final determinations are done by hydride AAS from tartaric acid-solutions, except the ethanol fraction which is submitted to ETA-AAS. In the furnace, addition of HNO₃ and H₂O₂ and rapid heating in the gas-stop mode results in equal sensitivity of organic and inorganic tin in the ethanol extract. The proposed method is checked by coprecipitation/adsorption experiments and by addition of tin-bearing minerals to a natural sediment.The method was applied to fresh water sediments. In sediment cores, the KMnO₄ fraction was dominant, whereas in an oxic surface sediment NH₄I releases the main fraction (cassiterite).     

Semiconductor‐photocatalyzed degradation of carboxylic acids: Enhancement by particulate semiconductor mixture

Degradation of oxalic acid on particulate TiO₂, ZnO, CuO, Bi₂O₃, In₂O₃, and Nb₂O₅ under UV‐A light exhibits first‐order kinetics, and the degradation rates increase linearly with the photon flux. All the oxides show sustainable photocatalytic activity, and the photonic efficiencies of degradation of oxalate are very much lower than those of the acid. The ease of degradation of carboxylic acids is the following: formic > oxalic > acetic > citric. Intimate mixtures of two different particulate semiconductors kept under suspension and at continuous motion exhibit higher photocatalytic activity, revealing interparticle charge transfer. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 716–726, 2009