Results 161 to 170 of about 63,548 (216)
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Nature, 1963
THE idea that humic acids are heteropolycondensates1 of phenolic substances with or without the participation of amino-acids is now widely accepted. Three possible sources of the phenols are postulated: (1) phenolic materials such as flavonoids leached from the plant debris; (2) phenolic units formed during the decomposition of lignin; (3) phenolic ...
A, BURGES +4 more
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THE idea that humic acids are heteropolycondensates1 of phenolic substances with or without the participation of amino-acids is now widely accepted. Three possible sources of the phenols are postulated: (1) phenolic materials such as flavonoids leached from the plant debris; (2) phenolic units formed during the decomposition of lignin; (3) phenolic ...
A, BURGES +4 more
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Plant and Soil, 1972
An explanation has been advanced for the previously reported observation that alkaline hydrolysis of humic acids will release amino acids that are resistant to acid hydrolysis. It is thought that under the alkaline conditions oxidation of N-phenyl-amino acids to the more readily hydrolysed quinonimines occurs.
T. J. Piper, A. M. Posner
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An explanation has been advanced for the previously reported observation that alkaline hydrolysis of humic acids will release amino acids that are resistant to acid hydrolysis. It is thought that under the alkaline conditions oxidation of N-phenyl-amino acids to the more readily hydrolysed quinonimines occurs.
T. J. Piper, A. M. Posner
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Tetrahedron, 1967
Abstract The action of water and acids on “humic acid” (HA) is described, and it is concluded that HA is a complex of a polycyclic aromatic “core” responsible for the ESR spectrum which is attached to polysaccharides, proteins, relatively simple phenols and metals.
M.V. Cheshire +4 more
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Abstract The action of water and acids on “humic acid” (HA) is described, and it is concluded that HA is a complex of a polycyclic aromatic “core” responsible for the ESR spectrum which is attached to polysaccharides, proteins, relatively simple phenols and metals.
M.V. Cheshire +4 more
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Tetrahedron, 1967
Abstract Alkaline solutions of “humic acid” (HA) isolated from some eighty different soils and peats give ESR spectra indicative of the presence of remarkably stable semiquinone ion radicals. The type of spectrum is largely determined by the pH of the soil but not by the age of the soil or the nature of the plant cover, and the examination of the HA ...
N.M. Atherton +3 more
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Abstract Alkaline solutions of “humic acid” (HA) isolated from some eighty different soils and peats give ESR spectra indicative of the presence of remarkably stable semiquinone ion radicals. The type of spectrum is largely determined by the pH of the soil but not by the age of the soil or the nature of the plant cover, and the examination of the HA ...
N.M. Atherton +3 more
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Tetrahedron, 1971
Abstract The synthesis is described of quinones containing α-amino acid ester substituents and the structure of the products is established by NMR and mass spectroscopic techniques. Hydrolysis of the products with 6N HCl has been studied; the products behave as vinylogous amides but the release of nitrogen in the form of amino acid is low ...
P.A. Cranwell, R.D. Haworth
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Abstract The synthesis is described of quinones containing α-amino acid ester substituents and the structure of the products is established by NMR and mass spectroscopic techniques. Hydrolysis of the products with 6N HCl has been studied; the products behave as vinylogous amides but the release of nitrogen in the form of amino acid is low ...
P.A. Cranwell, R.D. Haworth
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Electrochemical degradation of humic acid
Science of The Total Environment, 2000The treatment of natural water for drinking water production goes through the degradation of humic substances. In this study, humic acid, extracted from a peat area located at the margins of the Mogi Guaçu River at São Paulo State, Brazil, was used to perform electro-oxidation essays in order to evaluate the possibilities of electrochemical methods in ...
A J, Motheo, L, Pinhedo
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Tetrahedron, 1968
Abstract The effect of KOH fusion, pyrolysis, and hydriodic acid on acid boiled humic acid (ABHA) has been studied. As many of the products of the KOH fusion of ABHA are obtained similarly from the “polymers” of o - or p -benzoquinone or furfural, it is probable that the fusion products shed little, if any, light on the constitution of HA.
M.V. Cheshire +2 more
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Abstract The effect of KOH fusion, pyrolysis, and hydriodic acid on acid boiled humic acid (ABHA) has been studied. As many of the products of the KOH fusion of ABHA are obtained similarly from the “polymers” of o - or p -benzoquinone or furfural, it is probable that the fusion products shed little, if any, light on the constitution of HA.
M.V. Cheshire +2 more
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Desmutagenic effect of humic acid
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 1986In the present study, humic acid was not found to be mutagenic and did not inhibit spontaneous mutation. It did, however, inhibit the mutagenicities of benzo[a]pyrene and 3-aminoanthracene (+S9 mix), but not the mutagenicities of 4NQO, AF-2 and MNNG (-S9 mix).
T, Sato, Y, Ose, H, Nagase
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Environmental Toxicology and Chemistry, 1991
Abstract Iodide binding by humic acid was studied. The reaction was dose, temperature and pH dependent. A maximum binding of 88% was reached with 2 mg humic acid in 0.15 M Tris buffer. The efficiency of iodide binding by the buffer becomes higher whenever the buffer is slightly alkaline.
Tien-Shang Huang, Fung-Jou Lu
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Abstract Iodide binding by humic acid was studied. The reaction was dose, temperature and pH dependent. A maximum binding of 88% was reached with 2 mg humic acid in 0.15 M Tris buffer. The efficiency of iodide binding by the buffer becomes higher whenever the buffer is slightly alkaline.
Tien-Shang Huang, Fung-Jou Lu
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Methylation of Humic Acid Fractions
Science, 1978A new three-step permethylation procedure for humic acid fractions has been developed. In the first step, carboxylic acid groups are methylated with diazomethane in dimethylformamide; in the second step, hydroxyl groups are methylated with methyl iodide and dimethyl sulfinyl carbanion in dimethylformamide; and in the third step, acidic groups ...
R L, Wershaw, D J, Pinckney
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