Showing papers on "Oxalic acid published in 1990"

Characterization by high performance liquid chromatography (HPLC) of the solubilization of phosphorus in iron ore by a fungus

Abstract: The value of iron ore is adversely affected by phosphorus in concentrations over 0.03% by weight. The present research concerns the use of metabolic products of aPenicillium-like fungus to leach insoluble phosphates (hydroxyapatite) from ores. Ion chromatography was used to measure metabolism of glucose into acidic fragments. The rate and products of glucose degradation depended on both the chemical composition of the growth medium (buffered or not) and incubation conditions (shaken or quiescent). The principal products were identified as oxalic acid and isomers of propylene dicarboxylic acid, mainly itaconic acid. Continued, slow metabolism of itaconic acid generates more oxalic acid. Aliphatic acids were not detected. Both iron ore phosphate and calcium phosphate were partially solubilized by either the spent broth or aqueous oxalic acid. Solubilization of ore phosphorus was greatly assisted by hydrochloric acid added to the spent broth in small increments. The data suggest biological alternatives to costly leaching procedures that use only mineral acids.

Effects of aluminium on tap-root elongation of soybean (Glycine max), cowpea (Vigna unguiculata) and green gram (Vigna radiata) grown in the presence of organic acids

Abstract: The role of fulvic, malic, and oxalic acids in alleviating the toxic effects of aluminium (Al) on tap-root elongation of soybean cv. Fitzroy, cowpea cv. Vita 4, and green gram cv. Berken was studied. Treatments consisted of a factorial combination of four Al concentrations (0, 12.5, 25 and 50 µM as Al(NO3)3 • 9H2O) and two concentrations either of malic or oxalic acid (0, 50 µM) or fulvic acid (0, 65 mg L−1 of organic carbon). The free monomeric Al in solution was determined using a pyrocatechol violet procedure which distinguishes between monomeric and organically complexed Al. Fulvic acid completely alleviated the toxic effect of Al at all concentrations on soybean and cowpea and at concentrations <25 µM on green gram. The non-toxic Al-fulvate complex remained in solution. Both malic and oxalic acid, at the concentrations tested, failed to alleviate Al toxicity on any species; a much higher proportion of the added Al remained in monomeric form in the presence of these acids

Determination of ammonium and other major cations in river and rain water by ion chromatography using silica gel as an ion exchanger.

Abstract: The separation of NH4+ from Na+, K+, Mg2+ and Ca2+ on silica gel columns was investigated using natural water samples and lithium oxalate as a retention modifier. The pore size of silica gels was found to be the most important factor affecting the retention of the cations. When a 0.0025mol dm-3 lithium oxalate solution of pH 7 was used as the mobile phase these cations could be completely separated on a short silica-gel column (Develosil 30-3, 35mm×4.0 mm i.d.) within about 20min. NH4+ contents in river (0.01-0.27ppm) and rain (1-1.8ppm) water samples were determined successfully.

Structure of the oxalate ion

Abstract: While the oxalate ion is planar in some crystalline oxalates, it is twisted in others, with variable twist angles between the carboxylate groups. Calculations by AM1 and ab initio procedures have now shown free oxalate ion to have an orthogonal D2h structure. Introduction of disembodied charges (“sparkles”) as models of metal cations reduces the twist angle and zinc oxalate is calculated to be planar, like oxalic acid. The hydrogen oxalate anion exists in two isomeric forms with similar energies, a planar form with cis hydroxyl and an orthogonal form with trans hydroxyl.

Study of factors affecting calcium oxalate crystalline aggregation.

Abstract: A study was made of the effects of citrate, pentosan polysulphate (a glycosaminoglycan) and mucin (a mucoprotein) upon crystalline growth and aggregation of calcium oxalate in synthetic urine. It was found that citrate inhibited aggregation. Pentosan polysulphate had no perceptible effect on aggregation but favoured the formation of calcium oxalate dihydrate crystals. Mucin enhanced the formation of large characteristic aggregates and also led to the formation of calcium oxalate dihydrate crystals. Particles of mucin in a solution served as a substrate on which several crystals of calcium oxalate dihydrate were formed by heterogeneous nucleation; the subsequent growth of these crystals resulted in the formation of large agglomerates.

speciation of Cadmium(II) Using Donnan Dialysis and Differential-Pulse Anodic Stripping Voltammetry in a Flow-Injection System

Abstract: A flow-injection/Donnan dialysis/differential pulse anodic stripping voltammetry system was developed for the determination of free cadmium concentrations, [Cd2+], in solutions containing organically complexed Cd(II). A small dialysis cell with a strong cation-exchange membrane separating the sample and the receiver channels, was equilibrated in a flow-injection system. The ionic strength of sample and receiver solutions was 0.1 M, with NaNO3 as the bulk electrolyte. By determining a constant fraction of the Cd2+ associated with the membrane phase, [Cd2+] of the samples could be measured. Experimentally determined [Cd2+] corresponded well with those calculated, using tabulated stability constants, when citric acid, nitrilotriacetic acid, and oxalic acid were added as ligands. Thus, negatively charged and uncharged complexes were excluded from the membrane. Using the experimental design presented, [Cd2+]>5 × 10×8 M could be determined, but there is a great potential for increasing the sensitivity ...

Preparation of LaNiO3 powder from coprecipitated lanthanum-nickel oxalates

Abstract: Coprecipitation of lanthanum and nickel oxalates in a water-alcohol mixed solution of an oxalic acid resulted in a simultaneous and homogeneous deposition of the respective oxalate particles with a desired cation ratio. The coprecipitated oxalate could be readily converted to a fine powder (5 to 6 m2 g−1) of the desired LaNiO3 by heating at 800 to 850° C. Detailed examination of some precipitation conditions established an optimum procedure needed for the powder synthesis of LaNiO3. Thermal analysis showed that La2NiO4 (high temperature form) is transiently produced prior to the formation of LaNiO3. Mixed valency of the nickel ion in the synthesized powders was quantitatively determined by means of the oxidation-reduction titration, suggesting that the chemical formula of the powders might be LaNiO2.85 to 2.90.

Preparation of high purity 110 K phase in the (Bi, Pb)-Sr-Ca-Cu-O superconductor system using a solution method

Abstract: A solution method has been demonstrated to purify the 110 K superconducting phase in the (Bi, Pb)-Sr-Ca-Cu-O system. Oxalic acid was used to chelate metal cations from the nitrates. The amount of chelating agent impacts the cation absorption in the precursor. The higher purity 110 K superconducting phase can be obtained in the shortest time and at the lowest sintering temperature. X-ray diffraction, resistivity and magnetization measurements all indicated positive evidence. The process can be expedited when the stoichiometry was enriched by calcium and copper. The preparation technique is considered valuable to purify multi-phase superconductors for mass production.

Ion chromatographic determination of sodium, potassium, magnesium and calcium ions in river water

Abstract: The factors affecting the ion chromatographic separation of the alkaline earth metal cations on silica gel columns were investigated using different types of dicarboxylic acids as retention modifiers. The mobile phase pH and acid concentration showed marked influence on the separation of the analytes. When a 0.002 mol dm −3 lithium oxalate solution of pH 7 was used as a mobile phase, the major four cations in river water (Na + , K + , Mg 2+ and Ca 2+ ) were completely separated on a Nucleosil column (50mm×4.6mm i.d.) within about 16 min.

Use of chemical fractionation and proton nuclear magnetic resonance to probe the physical structure of the primary plant cell wall.

Abstract: Proton magnetic resonance has been used to monitor the microscopic physical properties of etiolated hypocotyl cell walls from Phaseolus vulgaris L. at all stages in a series of chemical fractionations with ammonium oxalate and potassium hydroxide. Solid echo measurements indicate that 75% of the polymers in the intact cell wall, including the cellulose and most of the hemicelluloses, are arranged such that there is almost complete restraint of molecular motion. The chemical fractionations generally altered the physical structures of the remaining cell wall components. Digestion with 0.25% ammonium oxalate/oxalic acid solubilized the pectin and increased the mobility of the hemicellulose I component. Extraction with 4% potassium hydroxide removed the hemicellulose I component and loosened the hemicellulose II. Further extraction with 24% potassium hydroxide removed the hemicellulose II and loosened some of the cellulose. The cellulose crystallinity, as monitored by Jeener echo measurements decreased from 83% to 63% during these fractionations. We conclude that, while hemicellulose I is firmly attached to hemicellulose II, it is not in a closely packed structure. Hemicellulose II is strongly bound to cellulose and has a much more closely packed structure.

Formation of stable and highly resistive anodic oxides on InP

Abstract: When left in air, as‐grown anodic oxides grown under optimized conditions described in the literature have been found to age. It is shown that this is caused by a hygroscopic component in the outer indium‐rich layer of the oxide film. When oxalic acid is present in the forming electrolyte, this phenomenon is not observed: As‐grown oxides are stable and have a constant composition throughout their thickness. This paper discusses some of the properties of the oxide films, both as‐grown and annealed, and some aspects of the chemistry of their formation. This distinct behavior of oxalic acid can be attributed to the fact that it forms soluble complexes with In(III) in the relevant pH range.

Substituted acrylic-acid esters

Abstract: Substituted acrylic acid esters of the general formula (I) … … in which… R , R , R , R , X and Y have the meaning given in the description, their use for controlling pests, and novel intermediates. … Formula (I) provides a definition of the novel compounds which can be prepared by analogous processes, for example from suitable hydroxyacrylic acid esters with suitable alkylating agents, or from suitable substituted acetic acid esters with suitable formamides or derivatives thereof, or from suitable oxalic acid derivatives and suitable organometal compounds, or from suitable acrylic acid esters and suitable thiols. Some intermediates are also novel and can be prepared by analogous processes.

Radiolytic degradation of sorbic acid in isolated systems

Abstract: Effect of Co60γ-irradiation on stability of sorbic acid (SA) in solutions, dough and chapaties has been investigated. SA was highly susceptible to radiolytic degradation in aqueous systems. Rate of degradation decreased with rise in pH. Sugars, hydrocolloids except pectin, citric acid, lactic acid, malic acid, arginine and threonine, catalysed degradation while oxalic acid, maleic acid, Cu2+, nitrite, nitrate and phthalate had protective effects. SA was more stable in alcohols and vegetable oils than in aqueous solutions. In wheat flour radiolytic degradation of SA was less at lower moisture. Relatively SA was more stable in chapaties than in dough. Gelatinization and addition of oil in dough reduced degradation of SA.

Preparation and characterization of a zirconyl oxalate gel

Abstract: A zirconyl oxalate gel has been prepared in hydrochloric solution from aqueous solutions of oxalic acid and zirconyl chloride. This physical and thixotropic gel, dried at 40 °C, gives a powder which, when mixed with water, becomes again a gel. Further, it can be an interesting precursor of zirconia (46 wt% of the initial powder mass).

Simultaneous ion-chromatography of alkali, alkaline earth and heavy metal ions with conductivity and indirect UV detection: Comparison of eluents containing organic complexing acids and copper sulfate

Abstract: The simultaneous ion-chromatography of mono-and divalent metal ions on the weak cation-exchange column Nucleosil-PBDMA (polymer coated silica with polybutandiene-maleic acid) with conductivity and indirect UV-detection is presented. The influences of eluents containing organic complexing acids (α-hydroxy-isobutyric, tartaric, citric, oxalic, pyridine-2,6-dicarbonic acid and EDTA etc.) as well as UV-absorbing, displacing counterions [Cu(II), Ce(III) etc.] on the retention times of metal ions was investigated in detail. With the combination of citric acid-PDCA as eluent all alkali and alkaline earth ions could be completely separated within 12 min. Alkali, alkaline earth and heavy metal ions [Cu/Zn/Co/Fe(II)] were separated by the combination of tartaric and oxalic acid as eluent in a single run. Trace amounts of Na, K and Ca were successfully separated from the Mg-matrix by an EDTA-PDCA eluent. For the IC with indirect UV-detection the eluent consisting of CuSO4 or CuCl2 was used to separate Na, K, Mg and Ca with baseline resolution within 10 min.

Preparation of silica sols

Abstract: A low metals, very high purity Silica Sol having very low content of Fe, Al, Na, K, and other metals can be manufactured using a complexation technique with oxalic acid in the starting sodium silicate solution. This complex is then removed by passage through anion exchange resins while other impurities are removed by passage through cation exchange resins. The Silica Sols obtained can have less than 50 ppm each of Fe, Al, Na, and K, based on totals SiO₂.

Role of pyridoxine in oxalate metabolism.

Abstract: Oxalic acid, a dicarboxylate widespread in plants, plays no vital function in man and experimental animals. The animal system is endangered by the toxicity of oxalate, as this compound is not metabolized further in the body and is excreted as such in urine. Nonetheless, deposition of calcium oxalate is commonly found in end-state renal diseases owing to retention of oxalate.'22 The commonest pathological condition involving oxalate is the formation of calcium oxalate stones in the urinary tract (urolithiasis). Persistent hyperoxaluria is the most common feature in urolithiasis patients. It is well established that nutritional pyridoxine deficiency leads to hyperoxaluria and renal stone formation in experimental animals and In this paper, we discuss the role of pyridoxine in oxalate metabalism and illustrate the molecular mechanism(s) of hyperoxaluria in pyridoxine deficiency using the results of our studies over the past several years.

Oxidation of Coals in Liquid Phases. X. Mechanism of the Cleavage of Benzenecarboxylic Acids to Oxalic Acid and Carbon Dioxide by the Base-Catalyzed Oxygen-Oxidation

Abstract: A kinetic study of the oxidation of benzenecarboxylic acids has been performed in order to clarify the mechanism. The reaction products were oxalic acid and carbon dioxide, along with a trace of acetic acid. The oxidation rate of phthalic acid was proportional to the first order of the molality of phthalic acid, the molality of NaOH, and partial oxygen pressure, respectively; the apparent activation energy was 126 kJ mol−1. These results show that the rate-determining step is a cleavage of the benzene ring proceeded by a base-catalyzed oxygen-oxidation mechanism in which a carbanion formed by hydrogen extraction from an aromatic ring is attacked by oxygen. In the cleavage of phthalic acid, NaOH increases the selectivity to form oxalic acid as well as the oxidation rate. In the oxidation of 1,2,3-benzenetricarboxylic acid the same mechanism was recognized, but not for benzenehexacarboxylic acid which has no hydrogen on the benzene ring.