Showing papers on "Oxalic acid published in 1983"

Interactions of metal hydrous oxides with chelating agents

Abstract: Chelating agents, such as ethylenediaminetetraacetic acid (EDTA) and its thermal decomposition products [iminodiacetic acid (IDA), N(2-hydroxyethyl)iminodiacetic acid (HIDA)], and oxalic acid, enhance the dissolution of magnetite and hermatite at temperatures above 90°C. The mechanism involves three different processes: (a) acid dissolution assisted by the chelating agent, (b) reductive dissolution brought about by internal electron transfer between the ligand and the constituent Fe(III) ion complexes, followed by the released of Fe(II), and (c) additional autocatalytic dissolution by the ferrous-carboxylate complexes generated in solution by process (b). Hydrogen peroxide quenches pathway (c) by oxidizing dissolved Fe(II). The rates dissolution in the absence and in the presence of high H 2 O 2 concentrations allow for the evaluation of the relative importance of (a) and (b). Hydrazine greatly accelarated the overall dissolution rates through direct heterogeneous redox interaction with the surface Fe(III) ions. In all cases magnetic is more reactive than hematite. Rate constants are calculated for the various dissolution pathways and, in the case of heterogeneous electron transfer, the values are compared with those for analogous homogeneous reactions.

Heterogeneous electron transfer as a pathway in the dissolution of magnetite in oxalic acid solutions

Abstract: The dissolution of metal oxides is a process of importance in several fields such as hydrometallurgy, passivity of metals, and cleaning of boilers and metal surfaces in general. Oxalic acid is one of the most effective reagents for dissolution of magnetite under mild acid conditions. Magnetite is the oxide that confers passivity to steel surfaces. In the present communication, the more salient features of the mechanism of dissolution of magnetite by oxalic acid solutions are discussed with special focus on the role played by ferrous ions in the process. Oxalate plays an unique role among complexing carboxylic ligands in the dissolution of magnetite; it not only facilitates the electron-transfer reaction but also mediates in a relatively fast dissolution during the initial induction period (the induction period is much shorter than in the case of the dissolution of magnetite by ethylenediaminetetraacetic or nitrilotriacetic acid). This unique role has been used in the development of a very efficient scale removal formulation used in the decontamination of nuclear power plants.

Synthesis of oxalic Acid by enzymes from lettuce leaves.

Abstract: A rapid purification of lactate dehydrogenase and glycolate oxidase from lettuce (Lactuca sativa) leaves is described. The kinetics of both enzymes are reported in relation to their possible roles in the production of oxalate. Lettuce lactate dehydrogenase behaves like mammalian dehydrogenase, catalyzing the dismutation of glyoxylate to glycolate and oxalate. A model is proposed in which glycolate oxidase in the peroxisomes and lactate dehydrogenase in the cytosol are involved in the production of oxalate. The effect of pH on the balance between oxalate and glycolate produced from glyoxylate suggests that in leaves lactate dehydrogenase may function as part of an oxalate-based biochemical, pH-stat.

A simple technique for assessing the propensity for crystallization of calcium oxalate and brushite in urine from the increment in oxalate or calcium necessary to elicit precipitation.

Abstract: In an effort to develop a simple and reliable method with which to assess the propensity for spontaneous nucleation of calcium oxalate and brushite in urine, the permissible increment of oxalate and calcium was calculated. This represented the additional amount of oxalate or calcium that could be added to urine in three hours before spontaneous precipitation of calcium oxalate or brushite was initiated. The permissible increment of oxalate inversely correlated (P less than 0.001) with the formation-product ratio-activity-product ratio discriminant score of calcium oxalate, which was previously shown to reflect a quantitative measure of the likelihood for spontaneous nucleation. Similarly, the permissible increment of calcium inversely correlated (P less than 0.001) with the formation-product ratio-activity-product ratio discriminant score of brushite. The permissible increments in oxalate and calcium were significantly lower (P less than 0.001) in patients with renal stones than in control subjects. Moreover, treatment with thiazides, allopurinol, sodium cellulose phosphate, orthophosphate, and diphosphonate significantly raised the permissible increment of oxalate in patients with stones. Thus, the permissible increment was reliable in discriminating "stone-forming" from control urine and in assessing response to treatment.

Gamma Radiolysis of Aqueous Media and Its Effects on the Leaching Processes of Nuclear Waste Disposal Materials

Abstract: The effect of the presence of moderate gamma doses (6×104 Gy) on the leaching of glassy and ceramic waste forms has been investigated. It is found that the leach rates are enhanced by <50% in the case of alumina-free glasses, by a factor of 3 to 4 in the case of glasses that contain 5 to 8% Al2O3, and by a factor of 20 to 100 in the case of SYNROC-D (20% A32O3). Buffer studies show the enhancement to be almost entirely due to a decrease in pH, and the composition dependence of the enhancement factor is interpreted in terms of the sharp rise in both alumina solubility and leach rates of alumina-containing materials with increasing acidity. The radiation-induced pH decrease is partially due to the formation of nitric acid but formic and oxalic acid are also observed to be produced. The concentration of carboxylic acids is as large as that of HNO3. A mechanism is proposed that assumes HNO3 is produced due to the oxidation of dissolved nitrogen, while formic and oxalic acids result from the reduction ...

Process for preparing a diester of oxalic acid

Abstract: A process is disclosed for preparing a diester of oxalic acid by contacting carbon monoxide and an ester of nitrous acid in the vapor state under a pressure in the presence of a supported palladium monolith catalyst.

Method of removing copper and copper oxide from a ferrous metal surface

Abstract: A method of removing copper and copper oxide from a ferrous metal surface comprising contacting said metal and said copper oxide with an aqueous composition having a pH from about 3.0 to about 6.0 and comprising an oxidizing agent, a compound selected from the group consisting of oxalic acid, the alkali metal, and ammonium salts of oxalic acid and mixtures thereof, and an ingredient selected from the group consisting of citric acid, polyaminocarboxylic acids, the ammonium and alkali metal salts of citric acid and polyaminocarboxylic acids and mixtures thereof.

Use of dilute nitric acid solutions for treating certain skin lesions

Abstract: The composition consists of an aqueous solution of nitric acid and nitrous acid with a pH below 1 and an acid equivalent of from 6 to 10 mmole/ml; the amount of nitrous acid corresponds to 0.01 to 5 mg of nitrite (NO 2 - ) per ml. Additionally, the solution preferably contains acetic acid, oxalic acid and lactic acid as well as copper and cadmium ions. For the preferred composition, the preparation takes place by mixing the components and letting them react to the end or by an oxidative method, in the course of which nitrous acid is formed. The composition is suitable for the local treatment of superficial lesions of the skin and mucous membranes in the fields of cosmetics and medicine, particularly for certain malignant tumors. Experimentally, the effectiveness can be checked by two biological tests developed for this purpose.

Vapor pressures and lattice energies of oxalic acid, mesotartaric acid, phloroglucinol, myoinositol, and their hydrates

Abstract: In the present investigation, we report the enthalpy of dehydration and the enthalpy of sublimation of a number of organic hydrates and their anhydrous counterparts. These values are used to test the transferability of a set of atom–atom potential parameters, originally derived for carboxylic acids. The calculations showed that the parameter set was transferable to a fairly good degree.

The Formation of Oxalic Acid During Bleaching of Kraft Pulp

Abstract: Calcium oxalate scaling is a major practical problem in a paper mill, especially in the evaporators, pulp digesters, and the bleach room. The sources of oxalic acid were determined by analysis of mill samples. In the unbleached pulp mill, the source of oxalic acid is the wood. In addition, a major amount of oxalic acid was found to be formed in the bleach room. A laboratory bleaching study was undertaken to establish a quantitative relationship betweeen bleaching conditions and oxalic acid production. Hardwood kraft pulp was bleached using three sequences. The amount of oxalic acid produced was dependent upon the available lignin content of the pulp (Kappa number) and not the oxidant concentration or reaction temperature.

Hydrogen generator for motor vehicle

Abstract: Oxalic acid, dispersed in glycerol is heated to form formic acid which is then heated at a higher temperature to form hydrogen. By-product carbon dioxide is absorbed. The hydrogen is used directly with a fuel cell to produce electricity or as fuel for an internal combustion engine.

Wet strength resins

Abstract: Disclosed are novel wet strength resins for paper. The resins are produced by reacting an epihalohydrin, such as epichlorohydrin, with a polyaminopolyamide derived by reacting methylbisaminopropylamine with oxalic acid or mixture containing oxalic acid and one or more different saturated dicarboxylic acids or their esters.

Wet strength resin from aminopolyamide-polyureylene

Abstract: Disclosed are novel wet strength resins for paper. The resins are produced by reacting an epihalohydrin, such as epichlorohydrin, with an aminopolyamide-polyureylene intermediate derived by reacting methylbisaminopropylamine with oxalic acid or a diester of oxalic acid and with urea.

Alterations in circadian rhythmicity in calcium oxalate renal stone formers.

Abstract: The circadian (circannual for oxalic acid) variations of 13 urinary variables (volume, creatinine, calcium, oxalic acid, glycolic acid, 17-ketosteroids, 17-hydroxycorticosteroids, phosphates, urea, uric acid, chloride, sodium, and potassium) have been documented in 7 calcium oxalate renal stone formers and 7 healthy men (control group). Urine was collected every 4 h over a period of 24 h. All subjects had the same synchronization: diurnal activity from 07(00) to 23(00) +/- 1 h and nocturnal rest; meals were given at fixed clock hours (08(00), 12(30) and 20(00) +/- 1 h). A statistically-significant rhythm (p less than 0.05) was validated for all variables except urea and calcium in healthy men. In renal stone formers, 6 variables (calcium, oxalic acid, and glycolic acid in particular) had no detectable circadian rhythm. However, a periodicity of c. 8 h (ultradian rhythm) was demonstrated for calcium and oxalic acid with peaks being located around 02(00), 10(00), and 18(00). No circannual variations in oxalic acid output could be observed. The present study shows an alteration of the periodicity of calcium and oxalic metabolisms, i.e. the loss of a circadian (24-h) rhythm and the occurrence of an ultradian rhythm of 8 h. The risk of calcium-oxalate crystallisation appears thus greater at 02(00), 10(00), and 18(00). Furthermore, any study dealing with oxalic acid excretion should state the season of urine collection when comparing renal stone formers and healthy subjects, as significant differences in oxaluria may appear during the summer months and not during the rest of the year.

Method of polishing glass articles in an acid bath

Abstract: The method according to the invention of polishing glass in a polishing bath containing sulfuric acid and hydrofluoric acid permits long polishing times and thus reduced alternating treatments in polishing bath and washing bath at high polishing speed due to the fact that the polishing bath contains at least one acid which is stronger than the hydrofluoric acid, in particular acids whose dissociation constants are higher than that of the second dissociation stage of the sulfuric acid; preferably, oxalic acid is used. In order that the sulfuric acid concentration can be increased--in particular for glasses containing alkaline earth--0.1 to 5 g sodium chloride and/or potassium chloride per liter of polishing bath are added to the polishing bath during an 8-hour shift, either all at once or in portions.

Photo‐oxidation of Organic Compounds at Doped α ‐ Fe2 O 3 Electrodes

Abstract: Photo-oxidation of organic compounds at doped ..cap alpha..-Fe/sub 2/O/sub 3/ electrodes was investigated in aqueous and nonaqueous solutions. Oxalic and formic acids in 0.5M H/sub 2/SO/sub 4/ showed distinctly different reactivities. Photo-oxidation of alcohols, e.g., methanol and 2-propanol, was investigated in propylene carbonate and compared to their oxidation in water. The oxidation products (formaldehyde, acetone, and oxygen) were analyzed quantitatively; they accounted for 100% of the current. Competition between methanol and 2-propanol, and between these alcohols and water, is also reported. 18 references, 8 figures.

On the behaviour of nitrate esters in acid solution. III. Oxidation of ethanol by nitric acid in sulphuric acid

Abstract: The oxidation of ethanol as a model of the alcohols produced in the hydrolysis of nitrate esters, by nitric acid in aqueous sulphuric acid solutions has been studied with the aim to obtain information on the decomposition reaction of “spent acids”. The results show, in agreement with previous suggestions from this laboratory, that ethanol is firstly oxidized to acetaldehyde via a reaction initiated by nitric acid but carried on by NO2 radical. The latter is formed by the interaction of nitric and nitrous acids. The acetaldehyde is then oxidized by two independent paths leading one to acetic acid and the other to oxalic acid and eventually to CO2. The relevance of these findings on the understanding and on the control of „spent acids” is briefly discussed.

Pyridoxine therapy in patients with renal calcium oxalate calculi.

Abstract: In 12 patients with idiopathic calcium oxalate calculi pyridoxine was administered. Within six weeks mean daily oxalic acid excretion decreased from 480 +/- 122 mumol to 336 +/- 83 mumol. Glycolic acid excretion fell from 208 +/- 51 mumol to 153 +/- 26 mumol (normal range: oxalic acid 228-412 mumol/day, glycolic acid 130-290 mumol/day). The reduction of oxalic acid excretion seems to be beneficial in prevention of idiopathic calcium oxalate calculi.

Process for the preparation of a diester of oxalic acid

Abstract: In a process for preparing a diester of oxalic acid by the vapor phase catlytic reaction of carbon monoxide with an ester of nitrous acid in the presence of a catalyst composed of a solid carrier and a catalyst component supported on the carrier, the improvement wherein said catalyst component is composed of (a) a platinum-group metal or a salt thereof, and (b) at least one member selected from the group consisting of iron and an iron (II or III) compound, the atomic ratio of the component (a) to the component (b) as metal being from 10,000:1 to 1:4.

Aqueous solution of cationic thermosetting resin from N-bis(aminopropyl)methylamine/oxalic acid

Abstract: Disclosed are novel wet strength resins for paper. The resins are produced by reacting an epihalohydrin, such as epichlorohydrin, with a polyaminopolyamide derived by reacting methylbisaminopropylamine with oxalic acid or mixture containing oxalic acid and one or more different saturated dicarboxylic acids or their esters.