Showing papers on "Oxalic acid published in 1987"

Selective Formation of Formic Acid, Oxalic Acid, and Carbon Monoxide by Electrochemical Reduction of Carbon Dioxide

Abstract: Selective formation of formic acid, oxalic acid, and carbon monoxide by electrochemical reduction of carbon dioxide (CO2) is demonstrated using several metallic electrodes in aqueous and nonaqueous electrolytes. The electrode metals catalyze the electrochemical reduction of CO2 and are classified to three groups according to their main products from CO2. In and Pb electrodes as well as Hg electrodes are useful for the selective formation of formic acid by electrochemical reduction of CO2 in aqueous electrolytes. In the case of nonaqueous electrolytes, Pb, Hg, and Tl are useful for oxalic acid, and In, Zn, Au, and Sn electrodes are useful for carbon monoxide. Also, reaction mechanisms of CO2 electrochemical reduction are discussed.

Oxalic acid synthesis by the mycorrhizal fungus paxillus involutus (batsch. ex fr.) fr.

Abstract: Summary Oxalic acid produced by an isolate of the mycorrhizal fungus Paxillus involutus (Batsch. ex Fr.) Fr. in still broth culture was assayed using high-performance liquid chromatography. Production of oxalic acid per unit of mycelium was influenced by nitrogen source and concentrations of exogenous calcium and bicarbonate ions. Nitrate-grown mycelia produced large quantities of oxalic acid; ammonium-grown mycelia produced small quantities regardless of what other ions were present. Calcium concentrations between 10 and 50 meq 1−1 slightly enhanced oxalic acid production in the presence of nitrate; concentrations between 250 and 500 meq 1−1 depressed production. Small additions of bicarbonate ions substantially increased oxalic acids production when nitrate was present. When calcium was present, most of the oxalic acid was associated with the mycelium, probably as calcium oxalate. In the absence of calcium, most of the oxalic acid occurred free in the culture medium. It is concluded that in calcareous soils, bicarbonate and nitrate are more important than calcium in stimulating oxalate production. The significance and underlying mechanisms of oxalate production are discussed.

Hydrated copper oxalate, moolooite, in lichens

Abstract: Vivid blue inclusions in white whewellite or weddellite, occurring within the medulla of four lichen species growing on copper-bearing rocks, have been identified as the hydrated copper oxalate, moolooite, CUC204. nH20 (n ~ 0.4-0.7), by infrared spectroscopy and X-ray powder diffraction. The mineral is believed to have been formed by reaction between oxalic acid secreted by the lichen and ground or surface water containing copper.

Oxalic acid decreases calcium absorption in rats.

Abstract: Calcium absorption from salts and foods intrinsically labeled with 45Ca was determined in the rat model. Calcium bioavailability was nearly 10 times greater for low oxalate kale, CaCO3 and CaCl2 than from CaC2O4 (calcium oxalate) and spinach (high in oxalates). Extrinsic and intrinsic labeling techniques gave a similar assessment of calcium bioavailability from kale but not from spinach.

Biosynthesis and metabolism of ascorbic acid in plants

Abstract: The biosynthesis of L‐ascorbic acid in plants differs from that encountered in ascorbic acid‐synthesizing animals. Enzymic details are sparse, but in vivo studies with tracers clearly establish the stereochemical detail of both processes. Examples of each process are found in separate classes of algae. Plants utilize L‐ascorbic acid as the carbon source for the biosynthesis of two important plant acids, oxalic acid and L‐tartaric acid. Here, cleavage of L‐ascorbic acid between carbons 2 and 3 releases the 2 and 4 carbon intermediates. A second L‐tartaric acid‐synthesizing process peculiar to vitaceous plants, i.e., grape, cleaves ascorbic acid between carbons 4 and 5. The physiological significance of these metabolic interconversions is discussed. Other metabolic processes such as the oxidation/reduction properties of L‐ascorbic acid are also considered.

The role of the citric acid cycle in fungal organic acid fermentations.

Abstract: Filamentous fungi are well known for their potential to accumulate organic acids in the medium when supplied with large amounts of sugar. Commercial applications of this are the production of citric and itaconic acids. The present review attempts to present the current state of knowledge on the biochemical basis of organic acid accumulation by filamentous fungi (citric, itaconic, fumaric and oxalic acids), particularly with respect to the role of citric acid cycle reactions. The explanations offered are based on recent advances in understanding the compartmentation of the fungal cell, and regulation of some key enzymes. The general conclusion is that fungi accumulate organic acids by mechanisms which avoid the channeling of substrates into the citric acid cycle under conditions of strongly active glycolysis.

Solution and method for dissolving minerals

Abstract: A method of dissolving mineral salts comprising contacting the mineral salts with a solution of water, an additive consisting essentially of six moles of 1-hydroxyethane, 1, 1-diphosphonic acid mixed with one mole of hydroxymethylene phosphonic acid, phosphonoformic acid, sulfamic acid, oxalic acid, hydroxyacetic acid, 2-amino ethane sulfonic acid, or fluoroboric acid and neutralized to a pH of 7.0, and a polymeric dispersant.

Mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solutions.

Abstract: The mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solution was assayed with Salmonella typhimurium strains TA97, TA98, TA100, TA102 and TA104 in the presence and absence of S9 mix from phenobarbital- and 5,6-benzoflavone-induced rat liver Ozonated naphthoresorcinol was mutagenic in TA97, TA98, TA100 and TA104 without S9 mix By the addition of S9 mix, the mutagenic activity of ozonated naphthoresorcinol was markedly suppressed in TA98 and TA100, but became positive in TA102 High-performance liquid chromatography (HPLC) after derivatization to 2,4-dinitrophenylhydrazones demonstrated the formation of glyoxal as an ozonation product of naphthoresorcinol Ion chromatographic technique also demonstrated the formation of o-phthalic acid, muconic acid, maleic acid, mesoxalic acid, glyoxylic acid and oxalic acid as ozonation products The mutagenicity assays of these identified products with five Salmonella strains showed that glyoxal and glyoxylic acid were directly mutagenic; the former in TA100, TA102 and TA104, the latter in TA97, TA100 and TA104 In the presence of S9 mix, glyoxylic acid gave a positive response of mutagenicity for TA102 The experimental evidence supported that glyoxal and glyoxylic acid may contribute to the mutagenicity of ozonated naphthoresorcinol

The mechanism of thermal eliminations part XXIII: [1] The thermal decomposition of pyruvic acid

Abstract: The thermal decomposition of pyruvic acid into carbon dioxide and acetaldehyde is a unimolecular first-order reaction and takes place according to the rate equation, logk = 13.53–41,250/4.575 K. These parameters contrast markedly with those recently reported, viz. logk = 7.19–27,700/4.575 K and confirm that the latter, which gave an unacceptably low value for the frequency factor, are anomalous. The lower reactivity of pyruvic acid compared to oxalic acid is interpreted in terms of normal electronic effects.

Membrane cleaning compositions containing phosphorous compounds

Abstract: This invention pertains to the use of certain phosphorus compounds in conjunction with other materials which characterize cleaners of alkaline earth metal salts, metal oxide/hydroxide salts, and silica/silicate salts, particularly citric acid, malic acid, oxalic acid, ammonium bifluoride and sodium bifluoride. Amount of the phosphorus compounds is 0.5 to 70%, preferably 2 to 40%, based on 100% of a cleaner composition which includes the phosphorus compounds. Suitable phosphorus compounds are selected from aminoalkyl and hydroxyalkyl phosphonic acids and phosphonates, phosphonoalkanepolycarboxylic acids and salts thereof, polyphosphoric acids and salts thereof, and polyol phosphate esters.

Urinary organic acids: isolation and quantification for routine metabolic screening.

Abstract: A method for isolating organic acids from acidified urine on an equivolume mixture of Porapak Q and Porapak T is described, and results are compared with extraction with ethyl acetate and ion exchange on DEAE-Sephadex. Average recoveries of 14C-labeled oxalic acid, lactic acid, succinic acid, alpha-ketoglutaric acid, citric acid, and cinnamic acid were equal to or better than those obtained with the solvent-extraction method. The ion-exchange method gave higher recoveries for oxalic acid, lactic acid, and citric acid. The quantification of separated acids from reconstructed mass spectrometric ion traces is compared with quantification from the simultaneously recorded flame ionization detector response signals. A good correlation was obtained. With the present routine metabolic screening method we have detected several patients with inborn errors of metabolism.

A novel enzyme membrane electrode for oxalate determination in foodstuffs

Abstract: An enzyme membrane electrode usable for the assay of oxalate in foodstuffs is described. A commercially available preactivated polyamide membrane was used for the immobilization of oxalate oxidase. The bioactive disk thus obtained was associated with an amperometric transducer. The resulting self-contained enzyme electrode wich allows oxalate determination in various materials with minimal pretreatment exhibits a linear calibration ranging from 10–7 M and 10–4 M in the cell. The response-time was comprised between 20 seconds and 1 minute, depending on the oxalate content in the sample. The electrode-response was very stable for at least 4 months, a period during which more than 150 assays were performed. The results obtained with several food materials were in good agreement with those obtained with the conventional spectrophotometric method. Assays were also performed with a microprocessor-based analyzer normally used for glucose measurements with a glucose oxidase electrode When the analyzer is...

Process for manufacturing p-aminophenol

Abstract: A process for the reduction of nitrobenzene is described. The reaction is performed catalytically in an aqueous acid medium in the presence of a small amount of organic acid, such as a lower carboxylic acid, oxalic acid, methanesulfonic acid or trichloroacetic acid.

Measurement of urinary oxalate: an enzymatic and an ion chromatographic method compared.

Abstract: An ion chromatographic and an enzymatic method for determination of oxalic acid in urine were compared on the basis of reliability and practicability. Both methods displayed a within-run imprecision of under 5% and a total imprecision of under 10%. The mean recovery of 0.2 mmol/l sodium oxalate lay close to 100% for both methods. After 80 parallel determinations, both methods produced statistically identical results. In terms of cost per analysis, ion chromatography is the method currently preferred when large numbers of samples are involved. If only a few samples are to be analysed the enzymatic method--without any loss of reliability--can be employed.

Critical evaluation of a commercial enzyme kit (Sigma) for determining oxalate concentrations in urine.

Abstract: The Sigma reagent kit for urinary oxalate determination is reportedly simple, rapid, and specific for oxalate. We evaluated the kit and identified a number of shortcomings. Our investigations suggest that the recommended time for chromophore development is too short and should be doubled. Oxalate recovery during the extraction procedure depends strongly on urine pH. For complete extraction, urine should be acidified to pH 1.8-2.4. We also observed positive interference from ascorbate in urine. This interference was substantial, absorbances produced from ascorbate standards being approximately 80% of those obtained from oxalate standards of similar concentration. Our investigations also indicate the presence of a substance on the Sigma adsorbent that is eluted during the extraction procedure and interferes in the color reaction. These interferences represent potentially major sources of imprecision in the assay.

Spectrophotometric determination of traces of silicon in water after collection as silicomolybdenum blue on an organic-solvent-soluble membrane filter

Abstract: A rapid and simple preconcentration technique, based on collecting trace elements on a membrane filter and dissolving the membrane filter in an organic solvent, has been applied to the spectrophotometric determination of traces of silicon in water. Silicon, in the range of 1-14 ..mu..g as SiO/sub 2/ in 50 mL of water sample, is converted into ..cap alpha..-silicomolybdic acid and treated with a reductant solution containing tin(IV), L-ascorbic acid, and oxalic acid. The silicomolybdenum blue formed is collected on a nitrocellulose membrane filter in the presence of n-dodecyltrimethylammonium bromide. The membrane and the silicomolybdenum blue are dissolved in 5 mL of dimethylformamide (DMF), and the absorbance due to the silicomolybdate in the DMF is measured at 740 nm against a reagent blank. Phosphate in concentrations similar to that of silicate interferes, but moderate concentrations of arsenate and anionic surfactants and high concentrations of sodium chloride do not interfere. The detection limit is 0.13 ..mu..g of SiO/sub 2/ in 50 mL of sample on a 3..sigma../sub b/ basis.

Excessive myocardial calcinosis in a chronic hemodialyzed patient.

Abstract: Secondary oxalosis in chronic hemodialyzed patients is caused by impaired renal excretion and inadequate removal of oxalic acid during hemodialysis. Ascorbic acid is a precursor of oxalic acid. We report a parathyroidectomized patient with chronic renal failure, on hemodialysis, who received over a period of several months a total dose of 91.0 g ascorbic acid i.v. The plasma oxalic acid level in this patient was 14-fold higher than in healthy persons. Increased oxalic acid synthesis from its precursor ascorbic acid may be responsible for hyperoxalemia, high content of oxalic acid in myocardium, aorta and lung, and calcium oxalate deposition in soft tissues. Application of high doses of ascorbic acid should be avoided in hemodialysed patients with chronic renal failure.

Oxalic acid and calcium oxalate produced by Leucostoma cincta and L. persoonii in culture and in peach bark tissues

Abstract: Oxalic acid and crystals of calcium oxalate were produced during growth of Leucostoma cincta and L. persoonii on potato dextrose agar and in peach bark tissues. The identification of calcium oxalate was based on solubility characteristics, the results of KMnO4 titration, positive staining with silver nitrate – dithiooxamide, and crystal morphology as observed with light and scanning electron microscopes. Oxalic acid was detected by gas chromatography. This is the first report of oxalic acid production by both Leucostoma species causing peach canker. Calcium oxalate crystals observed on or near hyphae in culture were similar to crystals in artificially inoculated peach bark tissues. Addition of oxalic acid solutions alone to inner bark tissues caused maceration and necrosis. These results indicate a role for oxalic acid in the early stages of pathogenesis by Leucostoma spp. Tetragonal (bipyramidal) and prismatic calcium oxalate crystals formed on bark wounds treated with oxalic acid solutions were similar ...

Ozonation of organic refractory compounds in water in combination with UV radiation.

Abstract: The ozonation rates of organic refractory compounds such as aliphatic carboxylic acids and alcohols were determined in water at 293 K The experiment was carried out by recirculating a solution between an ozone absorption column and a rectangular ozone/UV reactor, and the time-dependent changes in concentration of organic substances were directly measured In the presence of UV radiation of about 30W•m-2, the initial ozonation rate of organic substances was increased by 10-104 times The total organic carbon was effectively decreased in the presence of UV radiation This was explained by the destruction of acetic and oxalic acid by HO radicals which were produced in the ozone/UV system The ozone/UV oxidation rate of acetic and oxalic acid was roughly proportional to the degree of dissociation