Showing papers on "Oxalic acid published in 1988"

Evidence for a cytoplasmic pathway of oxalate biosynthesis in Aspergillus niger.

Abstract: Oxalate accumulation of up to 8 g/liter was induced in Aspergillus niger by shifting the pH from 6 to 8. This required the presence of Pi and a nitrogen source and was inhibited by the protein synthesis inhibitor cycloheximide. Exogenously added 14CO2 was not incorporated into oxalate, but was incorporated into acetate and malate, thus indicating the biosynthesis of oxalate by hydrolytic cleavage of oxaloacetate. Inhibition of mitochondrial citrate metabolism by fluorocitrate did not significantly decrease the oxalate yield. The putative enzyme that was responsible for this was oxaloacetate hydrolase (EC 3.7.1.1), which was induced de novo during the pH shift. Subcellular fractionation of oxalic acid-forming mycelia of A. niger showed that this enzyme is located in the cytoplasm of A. niger. The results are consistent with a cytoplasmic pathway of oxalate formation which does not involve the tricarboxylic acid cycle.

Catalytic Dissoluion of Iron(III)(hydr)oxides by Oxalic Acid in the Presence of Fe(II)

Abstract: La dissolution d'hydroxydes de fer(III) (gœthite et hematite) est catalysee par les ions Fe(II). Cinetique et mecanisme de la reaction

Oxalate synthesis from soil bicarbonate by the mycorrhizal fungus Paxillus involutus

Abstract: The ability of the ectomycorrhizal fungusPaxillus involutus (Batsch ex Fr) Fr to utilize bicarbonate ions from solution, for oxalate synthesis was demonstrated using NaH14CO3 in a nitrate-nitrogen medium Fifteen percent of the carbonate ions incorporated was used for the synthesis of oxalic acid either directly from oxalacetate, or via citrate, isocitrate, and glyoxylate

Large electromechanical anisotropic modified lead titanate ceramics

Abstract: Modified lead titanate (PT) oxalates were prepared by mixing an ethanol solution with (calcium, lanthanum, neodymium, samarium or gadolinium) and titanium with an ethanol solution of oxalic acid containing lead, and (cobalt and tungsten) or manganese by blending. The resulting complex oxalate, after washing with ethanol for several times, was an amorphous powder with a very fine particle size. The amorphous coprecipitate gave, on calcining, a high sinterable modified lead titanate powder of compositions (Pb0.76Ca0.24) ((Co0.5W0.5)004Ti0.96)O3 or (Pb0.88La0.08) (Ti0.98Mn0.02)O3 which, on sintering, produced highly densified bodies (⩾98% theoretical density) at relatively low temperatures (1100 and 1150°C for Ca-PT and Ln-PT, respectively). Linear thermal expansion measurements, microstructural development of the modified lead titanates, and the influence of grain size onc/a ratio have also been studied.

Purification and Characterization of Oxalate Oxidase from Pseudomonas sp. OX-53

Abstract: Oxalate oxidase (EC 1.2.3.4) was purified to apparent homogeneity from Pseudomonas sp. OX-53. The molecular weight of the enzyme was about 320,000 by Sephadex G-200 column chromatography and 38,000 by sodium dodecyl sulfate disc electrophoresis. The isoelectric point of the enzyme was pH 4.7 by isoelectric focusing. This enzyme contained 1.12 atoms of manganese and 0.36 atoms of zinc per subunit. Besides oxalic acid, the enzyme oxidized glyoxylic acid and malic acid at lower reaction rates. The Michaelis constant of the enzyme was 9.5 mM for oxalic acid at the optimal pH 4.8. The enzyme was stable from pH 5.5 to 7.0. The enzyme was activated by flavins, phenylhydrazine, and o-phenylenediamine, and inhibited by I–, Br–, semicarbazide, and hydroxylamine.

Grafting of acrylamide onto guar gum using KMNO4/oxalic acid redox system

Abstract: The grafting of acrylamide onto guar gum in aqueous medium initiated by KMnO4/oxalic acid redox system has been studied gravimetrically at the temperature 35 ± 0.2°C. The effect of redox components, acrylamide concentration and quantity of guar gum has been studied in terms of percentage and efficiency of grafting. A plausible mechanism of grafting and a suitable rate expression has been suggested. The rate of grafting was found to increase with increase in temperature and concentrations of redox components and acrylamide, but, at high concentration of guar gum, the rate was found to decrease.

An inexpensive method for sensitive enzymatic determination of oxalate in urine and plasma.

Abstract: In this simple, sensitive, and rapid enzymatic method for the determination of oxalate in urine or plasma, oxalate oxidase (EC 1.2.3.4) prepared from barley seedlings is used to convert oxalate to carbon dioxide and hydrogen peroxide, which is determined photometrically at 600 nm, with use of horseradish peroxidase, by oxidative coupling of 3-methyl-2-benzothiazoline hydrazine with N,N-dimethylaniline. Plasma is pre-treated by ultrafiltration and co-precipitation of oxalate with calcium sulfate and ethanol, urine by dilution and reversed-phase chromatography on C18 columns. Analytical recovery for urine is 99 +/- 2%, for plasma 92 +/- 3%. The normal range for urinary excretion is 0.10 to 0.56 mmol/24 h, and for the concentration in plasma 0.4 to 3.7 mumol/L. There were no significant sex-related differences in urinary excretion or plasma concentration. Our within- and between-assay coefficients of variation were, respectively, less than 3.4% and less than 6.0% for urine, and less than 1.5% and less than 4.3% for plasma.

A method for the quantification of bacterial protein in the presence of Jarosite

Abstract: A variation on Peterson's modification of the Lowry method for microbial protein determination was developed in which 10% (w/v) oxalic acid was used to remove jarosite. This allowed the quantification of Thiobacillus ferrooxidans entrapped in solid jarosite or in aqueous suspensions containing jarosite. The quantity of protein measured was not affected by the amount of jarosite in the culture, the concentration of oxalic acid, or the time of exposure (up to 72 h) of the sample to oxalic acid. An application of this method was demonstrated in the quantification of biomass immobilized in jarosite on the surface of polystyrene beads in an inverse fluidized bed bioreactor used for the rapid microbial oxidation of ferrous iron.

Thermochemical conversion of polysaccharides in concentrated alkali to glycolic acid

Abstract: Degradation of starch and cellulose in alkaline solutions above 8N NaOH favored the production of glycolic acid. In 16N NaOH, starch and cellulose degraded at 240°C to produce, respectively, 46 and 43% yields of glycolic acid. At these same conditions, 24 and 12% yields of oxalic acid were also produced from starch and cellulose. Raising the amount of starch or cellulose above 10 g in 250 mL 16 N NaOH lowered the percent yields of glycolic and oxalic acids, but increased absolute yields sufficiently to consider larger polysaccharide: 16 N NaOH ratios for commercial use. Substituting KOH for NaOH lowered glycolic and oxalic acid yields, and demonstrated the effect of the alkali cation on the conversion reactions.

Process for producing perovskite-type oxides of the abo3 type

Abstract: A process for producing a perovskite-type oxide of the ABO 3 type is disclosed. A solution of an element A (Pb, Ca, Sr and/or La) and an element B (Ti and/or Zr) is brought into contact with oxalic acid in the presence of an alcohol to precipitate oxalic acid salts; the acid radicals in the solution are neutralized with an amine or ammonia; the resulting precipitate is then subjected to calcination. A fine-grained ferroelectric oxide having a sharp grain size distribution can be produced, with its chemcial composition being exactly controlled. This oxide is suitable for use as a piezoelectric, pyroelectric or ferroelectric material.

Americium removal from nitric acid waste streams

Abstract: Separations research at the Rocky Flats Plant /RFP/ has found ways to significantly improve americium removal from nitric acid/7M/ waste streams generated by plutonium purification operations. Partial neutralization of the acid waste followed by solid supported liquid membranes /SLM/ are useful in transferring and concentrating americium from nitrate solutions. Specifically, DHDECMP /dihexyl-N, N-diethylcarbamoylmethylphosphonate/ supported on Accurel polypropylene hollow fibers assembled in modular form transfers >95% of the americium from high nitrate /6.9M/, low acid /0.1M/ feeds into 0.25M oxalic acid stripping solution. Maximum permeabilities were observed to be 0.001 cm sec−1, consistent with typical values for other systems. The feed:strip volume ratio shows an inverse relationship to the fraction of metal ion transferred. Cation exchangers may be used to concentrate americium from the strip solution. Furthermore, OOD/iB/CMPO /or CMPO/ /octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide/ has been tested in an extraction chromatography mode. Preliminary results show CMPO to be effective in removing americium if the feed is neutralized to 1.OM acidity and iron/III/ is complexed with 0.20M oxalic acid.

Darstellung und Reaktionen von Thiooxalsäuren und Thiooxalsäurederivaten

Abstract: In this review the chemistry of sulphur-containing oxalic acid derivatives is summarized from the synthetic point of view. Thiooxalic acid derivatives can be prepared in the following ways: transformation of oxalic acid derivatives oxidation of C2 compounds, mainly derivatives of haloacetic acids formation of C[sbnd]C bonds between C1 compounds Thiooxalic acid derivatives are active and useful C2 synthons. The incorporation of sulphur atoms in oxalic esters increases their reducibility. 1,1-Dithiooxalic acid esters and amides, dithionooxalic acid esters, and, especially, tetrathiooxalic acid dimethyl ester are attacked by S- and C-nucleophiles at the thiono group (thiophilic attack) to form the oxidation stage of a thioaldehyde or sulphides, respectively. In cycloaddition reactions oxalic acid derivatives with one thiono function react as 2π-systems whereas dithiono- and tetrathio-esters may function as 2π- as well as 4π-systems. In comparison to their O-analogues thionooxalic acid derivatives po...

Corrosion behaviour of the aluminium alloy AA 6351 in glycol/water solutions degraded at elevated temperature

Abstract: A research programme has been developed to characterize the corrosion behaviour of the metals most widely used in solar collector systems. Common heat transfer fluids such as glycol/water solutions show a low aggressivity, unless pollution or high temperature exposure (degradation) occur. This paper deals with the study of the corrosion behaviour of the aluminium alloy 6351 (nominal composition: 1% Si, 0.6%Mg, 0.3% Mn, the balance Al) in ethylene or propylene glycol (EG or PG)/water solutions (1:1 in volume) degraded at 108°C in contact with AA 6351 as glycol oxidative degradation catalyzer. The tests in degraded solutions, performed at 80°C over a period of 60 days, showed that degradation causes an increase in the uniform corrosion rates and a remarkable pitting attack. Pitting corrosion has been mainly attributed to the action of copper ions dissolved from the aluminium alloy and detected in the solutions by atomic adsorption analysis. In conjunction with the degradation studies, tests were also performed at 80°C in buffered PG/water solutions (pH 4) containing the acids reported to be produced during the process of glycol oxidative degradation (oxalic, glycolic, acetic and formic acids), at the concentrations 10−3 or 10−2 M. In these solutions the corrosion behaviour of AA 6351 was investigated over a period of 30 days by measuring the gravimetric corrosion rates and the polarization resistance values and by recording the polarization curves after 2 h or 30 days of immersion. Only oxalic acid and 10−2 M glycolic acid significantly increased the AA 6351 corrosion rates, but only in the first period of immersion. On the contrary, when the surface films were formed in the solutions of these acids, they afforded the highest protectivity. The analogous behaviour of AA 6351 in oxalic and glycolic solutions has not been attributed to the formation of an insoluble aluminium salt film with the organic anions, but rather to the growth of an oxide film with peculiar characteristics of thickness and protectivity.

Coprecipitation method for producing superconducting oxides of high homogeneity

Abstract: A homogenous coprecipitation method by which superconducting oxides having perovskite-like structure, such as YBa2Cu307-x, can be produced in mass, in which urea is used as solvent to adjust and control the PH value of an aqueous nitrate solution The coprecipitation method of this invention comprises following steps: (a) preparing an aqueous mixture containing Y, Ba and Cu salts with molar ratio of 1:2:3 wherein Y being 0068M; (b) adding 5-10 moles of oxalic acid per one mole of Y and 20-250 moles of urea per moles of Y into the aqueous mixture; (c) heating the aqueous mixture to a temperature range of 80° to 100° C to proceed a hydrolysis of the urea such that PH value of the aqueous mixture will be gradually elevated by NH 3 gas evoluted from the urea hydrolysis; and (d) cooling the temperature of the aqueous mixture to room temperature at which time a desired uniform PH value is reached After cooling, pale blue homogeneous coprecipitates of the superconducting oxides can be obtained

Urinary biochemical profile of patients with ureteric calculi in Jodhpur region (north western India)

Abstract: Urine chemistry of 42 normal subjects (NS) and 59 ureteric stone formers (SF) from Jodhpur region of Rajasthan, India is presented. Twenty four hour urinary levels of calcium, oxalic acid and uromucoids were significantly higher and levels of magnesium, citric acid and inorganic phosphorus were significantly lower in SF as compared to NS. No significant difference was observed in the uric acid, sodium and potassium levels in the two groups. Significant correlation was observed between calcium and magnesium; calcium and oxalic acid; calcium and citric acid; magnesium and oxalic acid; and oxalic acid and citric acid in NS on the basis of mmol/l but not on the basis of mmol/24 h. Calcium and oxalic acid correlation was uninfluenced by magnesium and citric acid levels. The log of risk factor index (RI) was higher (p< 0.001) in SF (−1.652) as compared to NS (−2.103). The log of ion activity product (IAP) was also higher (p< 0.001) in SF (−3.192x10−3) than in NS (−2.914x10−1). Based on RI and IAP, a scale has been devised for the prediction of the risk of stone formation and recurrence.

Elastomer-compatible oxalic acid acylated alkenylsuccinimides

Abstract: Disclosed are elastomer-compatible mono- and bis-alkenylsuccinimide oxamides dispersants prepared by reacting a polyalkyleneamine succinimide with an amount of oxalic acid sufficient to react with at least 30 percent of the reactive nitrogens on the succinimide chain.

Magnesia cement mixture

Abstract: A magnesia cement mixture containing calcined (burnt) magnesite (magnesium oxide) and pulverulent pozzuolana (pozzolana) or silica (siliceous earth) or water glass, contains as further additive either water-soluble phosphates or oxalic acid or citric acid or mixtures of these materials. The mortar then formed is water-resistant and does not tend to form expansion cracks.