Showing papers on "Oxalic acid published in 1995"

Graft polymerization of acrylic acid onto starch using potassium permanganate acid (redox system)

Abstract: Graft polymerization of acrylic acid (AA) onto rice starch using postassium permanganate/acid redox system as initiator was investigated. When starch was reacted with KMnO4 solution, MnO2 was deposited onto starch. The dependence of MnO2 amount deposited was directly related to KMnO4 concentration. Subjecting the MnO2-containing starch to a solution consisting of monomer (AA) and acid (citric, tartaric, oxalic and hydrochloric acid) formed poly(AA)–starch graft copolymers. The graft yield, expressed as meq COOH/100 g starch, was measured by the amount of MnO2 deposited, AA concentration, material-to-liquor ratio, kind and concentration of acid, as well as temperature and duration. Finally, the newly prepared poly(AA)–starch graft copolymers were applied to cotton textiles to determine their suitability as sizing agents. The highest graft yield was obtained with citric acid and the least with hydrochloric acid, with tartaric and oxalic acid in between. The graft yield increased by increasing the concentration of acid to a certain concentration beyond which grafting leveled off. A similar trend was observed when the magnitude of grafting was related to the amount of MnO2 deposited. The graft yield increased by increasing the polymerization temperature from 30° to 50°C. Increasing the temperature to 60°C is accompanied by decreased grafting. On the other hand, fabric samples sized with poly(AA)–starch graft copolymers acquire higher tensile strength, elongation at break, and abrasion resistance than that sized with native rice starch, i.e., poly(AA)–starch graft copolymers serve as good sizing agents for cotton textiles. A tentative mechanism for grafting rice starch with AA using the KMnO4/acid redox system was elucidated. © 1995 John Wiley & Sons, Inc.

Degradation of oxalic acid by transgenic oilseed rape plants expressing oxalate oxidase

Abstract: Oxalic acid is thought to have a primary role in the pathogenicity of several plant pathogens, notably Sclerotinia sclerotiorum. A gene coding for the enzyme oxalate oxidase was isolated from barley roots and introduced into oilseed rape as a means of degrading oxalic acid in vivo. This report describes the production of several transgenic plants of oilseed rape and the characterisation of these plants by Southern, Western and enzyme activity assays. Plants were shown to contain an active oxalate oxidase enzyme and were tolerant of exogenously supplied oxalic acid.

Evolution of Hematite Surface Microtopography Upon Dissolution by Simple Organic Acids

Abstract: The surface microtopography of hematite over the course of dissolution in oxalic and citric acids was examined by in-situ and ex-situ atomic-force microscopy, ln-situ imaging of the basal-plane surface of a centimeter-scale natural hematite sample immersed in 2 mM citric acid demonstrated that the basal-plane surface was relatively unreactive; rather, dissolution occurred along step edges and via etch-pit formation. Ex-situ imaging of synthetic hematite particles following batch dissolution in 1 mM oxalic acid showed similar dissolution features on basal-plane surfaces; in addition, etching along particle edges was apparent. The presence of etch features is consistent with a surface-controlled dissolution reaction. The results are in agreement with previous investigations suggesting that the basal-plane surface is relatively unreactive with respect to ligand exchange. Both in-situ and ex-situ imaging of particle surfaces can provide valuable information on the roles of surface structures and microtopographic features in mineral dissolution.

Mechanism of Resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) in Chickpea: Role of Oxalic Acid m Leaf Exudate as an Antibiotic Factor

Abstract: Mechanisms of resistance to Helicoverpa armigera Hubner in chickpea, Cicer arietinum L., were investigated. Inhibition of larval growth occurred in a feeding test using the leaves of chickpea genotypes, which had previously been identified as having resistance to H. armigera . A feeding test using unwashed and washed leaves revealed that the substance responsible for the growth inhibition was water soluble and present on the surface of the leaves. Acid components of the leaf exudate were analyzed by high-performance liquid chromatography. Oxalic acid and malic acid were detected as major components in all 4 genotypes that were analyzed. Genotypes resistant to H. armigera accumulated more oxalic acid on the leaves than susceptible genotypes. Oxalic acid showed significant growth inhibition on H. armigera larvae when included in a semi-artificial diet. The accumulation of oxalic acid is considered to be one of the mechanisms of H. arnigera resistance in chickpea. Inhibition of larval growth by oxalic acid was not caused by antifeedant effects but was more likely attributable to antibiosis. Malic acid had no effect on larval growth.

Zur Aminolyse von Bis‐Imidoylchloriden der Oxalsäure. I. Umsetzung mit aromatischen und aliphatischen Aminen

Abstract: On the Aminolysis of Bis-Imidoylchlorides of Oxalic Acid. Part I. Reaction with Aromatic and Aliphatic Amines The reaction between bis-imidoylchlorides 2 derived from oxalic acid and several aromatic and aliphatic amines was investigated. While primary aromatic amines need a thermical activation by refluxing, primary aliphatic amines give mainly at room temperature the amidines 3 in moderatly up to good yields. Proceeding from enantiomeric pure amines e.g. (R)- or (S)-1-phenethylamine the new homochiral oxalic amidines 3y and 3z with C2-symmetry were obtained. Several secondary amines react with the bis-imidoylchloride 2a to give via intramolecular cycloacylation derivatives of isatine. The new synthesized amidines 3 perform systems with a strong molecular dynamic like prototropie and E/Z-interconversion. All new compounds described were characterized by elemental analysis and spectroscopic methods.

Process and installation for the destruction of organic solutes, particularly complexing agents, present in an aqueous solution such as a radioactive effluent

Abstract: The invention relates to a process and an installation for the destruction of organic solutes, particularly complexing agents, present in an aqueous solution such as a radioactive effluent. According to this process, the aqueous solution undergoes electrolysis in a cell (1) comprising a working electrode (51, 52, etc.) by applying to said electrode an adequate potential for destroying the solutes by electrolytic oxidation and periodic modification takes place to the potential applied or to the passage direction of the current passing through the cell so as to periodically carry out a regeneration of the working electrode. The solutes can be organic acids such as formic acid, dihydroxymalonic acid or oxalic acid.

Oxalylamino-benzofuran- and benzothienyl-derivatives

Abstract: The inventive Oxalylamino-benzofuran- and benzothienyl-derivatives are prepared by reacting the appropriate amino substituted benzofuranes and benzothiophenes with oxalic acid derivatives. The inventive compounds are suitable for the prevention and treatment of acute and chronic inflammatory processes, particularly of the airways.

Effect of nitrogen application on the contents of sugars, ascorbic acid, nitrate and oxalic acid in spinach (Spinacia oleracea L.) and komatsuna (Brassica campestris L.)

Abstract: Spinach and komatsuna were cultivated with 0, 10, 15 and 30g N m(-2) applications in an Andosol, and the changes of the contents of sugars. Ascorbic acid, nitrate and oxalic acid which are the constituents related with the quality of the vegetables, and the relations between the growth (fresh weight), nitrogen status and the contents of these constituents were investigated. Ascorbic acid is contained both in spinach and komatsuna, but oxalic acid is contained at a high level in spinach and at t race levels in komatsuna. In spinach, the total (water-soluble plus insoluble) oxalic acid content was increased in the leaf blades and decreased in the leaf petioles along with the increase of nitrogen application, and there was no difference in the whole leaves with the treatments. The contents of sucrose and ascorbic acid were high in the plants in which yield and nitrogen content were low and dry matter content was high. In view of the quality of spinach and komatsuna, the low nitrogen application is better, but the amount of nitrogen application must be determined considering the maintenance of growth and yield

Acid-base fuels for self heating food containers

Abstract: An exothermic, hydratable fuel mixture for a self-heating food container (10) comprises particles (27) of a base such as lime and an acid such as oxalic acid. When water (29) is added to the mixture, exothermic heat is generated by hydration of the lime and neutralization reaction between the lime and the acid to produce a non-hazardous residue salt. Mixtures of bases and mixtures of acids can be used to optimize the heating characteristics of the fuel mixture.

Ozonolysis Of Humic Acid And Its Effect On Decoloration And Biodegradability

Abstract: The objectives of this research were to investigate the reactivity of humic acid (HA) with ozone and to evaluate its effect on decoloration and biodegradability. Reagent HA was selected as a target compound, and the change in overall water quality parameters, molecular weight distribution, color and biodegradability during ozonation were investigated. Partial oxidation such as decoloration was observed, though the complete destruction represented by TOC removal was not significant. The rate of ozone usage decreased as the reaction proceeded. Degradation to the lower molecular weight fragments was confirmed by ultrafiltration. The close relationship between color and fragmentation was verified. Decoloration was represented by a pseudo-first order reaction. Formic, acetic, oxalic and glyoxylic acids were identified by HPLC and ion chromatography as typical low molecular weight organic acids. The biodegradability of ozonated HA solutions, represented in terms of the ratio of BOD5 to TOC, was improved.

SERS of dicarboxylic acids on silver sols

Abstract: SERS spectra of succinic and oxalic acids on silver sols have been revised. For the latter molecule the vibrational spectrum has been assigned on the basis of AM1 and 3-21G ab initio force field calculations. Also, SERS of the malonate ion is presented for the first time, showing some general characteristics similar to the aforementioned. The results have been analysed together, and a model is proposed in which the interaction with the surface is through one carboxylate group in the case of oxalic acid and through both carboxylate groups in the case of malonic and succinic acids.

Leaching of iron and toxic heavy metals from anaerobically-digested sewage sludge

Abstract: Heavy metal-loaded sewage sludge was leached abiotically using FeCl2 and FeCl3 which are applied in waste water treatment plants to eliminate phosphate and for coagulation. Due to the hydrolyzing nature of ferric iron, ferric chloride (100 mmll L−1) was able to solubilize more than 90% of copper and zinc and more than 80% of cadmium, with an optimal pulp density of 3% (w/v), after 10 h of exposition at 25°C. Chromium, lead and nickel were solubilized to an extent of 40–70%. With the exception of copper (redoxolysis), all heavy metals monitored were leached following the principle of acidolysis. Chemical leaching with iron resulted in a secondary contamination of sewage sludge (96 g iron per kg dry weight). The insoluble iron compounds which were precipitated for adsorbed to sludge flocks could be resolubilized with oxalic acid (100 mM, pH<3.3) up to an extent of 90%. Iron was leached by acidolysis and held in solution by complexation with oxalic acid. The pH optimum for the treatment of sewage sludge with 100 mmol L−1 oxalic acid was ≈pH 3.3. At this pH an excessive solubilization of nutrient elements and compounds (phosphorus, nitrogen, alkali and alkali earth elements) could be avoided concomitantly leaching 75% iron. Furthermore the hydrophobicity of the sewage sludge was significantly reduced as a result of treatment with iron chloride.Thiobacillus ferrooxidans (isolated from arsenopyrite and adapted on sewage sludge) utilized ferrous iron as an energy source in the presence of chloride ions (FeCl2) as efficiently as ferrous sulphate. No toxic effects of oxalic acid onT. ferrooxidans were observed at the prevailing concentration.

Characteristics of catalyst for carbon monoxide coupling reaction

Abstract: The use of carbon monoxide to produce organic compounds is an important research area for the future. In particular the carbon monoxide coupling reaction takes place at moderate reaction conditions,with low consumption of energy, to produce oxalic acid and oxalate. The chemicals are feedstocks for ethylene glycol synthesis by hydrogenation of oxalate, as well as for products such as pesticides, pharmaceuticals, foodstuffs, polymers, and fine chemicals. The carbon monoxide coupling reaction on supported metal catalysts Pd/Al{sub 2}O{sub 3} and Pd-Fe/Al{sub 2}O{sub 3} was used to study the characteristics of the catalyst under different conditions. The results indicated that the catalytic activation temperature influenced the catalytic activity and that there was an optimum activation temperature. The characteristics of effective coupling catalysts were found to be smaller surface areas and bigger pores, for example the {alpha}-phase of aluminum oxide. X-ray photoelectron spectroscopic analysis results show that the catalytic reaction of CO coupling occurs via a redox mechanism.

Selective chemical etching in microelectronics fabrication

Abstract: The present invention relates to a chemical etchant for etching metals in the presence of one or more metals not to be etched, the etchant comprising 10-25 gms EDTA, 15-35 gms K 2 HPO 4 and 25-45 gms oxalic acid in a liter of 30% H 2 O 2 . More particularly, in the fabrication of interconnections for microchip structures, the present invention addresses the removal of intermediate adherent layers, e.g., Ti--W, without damaging other microchip structures made of other metals, such as Al or Al--Cu test pads; Cu and phased Cr--Cu layers; and Sn--Pb solder bumps. The use of potassium phosphate in the hydrogen peroxide+EDTA bath has been found to significantly reduce the attack on the metal not to be etched. Furthermore, the use of oxalic acid in the bath prevented the deposition of tin oxide on the substrate adherent layer metal, thus facilitating its complete removal.