Showing papers on "Ferric published in 1973"

Paleoecological Significance of the Banded Iron-Formation

Abstract: Banded iron-formation (BIF) is rare in rocks younger than about 2 aeons (years X 10 9 ). It records a major episode of chemical iron sedimentation, however, at about 2 to 2.1 aeons, just before the deposition of the oldest oxidized terrestrial sediments. The great iron-formations of this age reflect dramatic events. Ferrous iron residual in stagnant oceans beneath an anoxygenous atmosphere may then have moved into the photic zone on a vast scale because of overturning instigated by climatic change. A previously limited, photosynthetic, procaryotic microbiota, dependent on ferrous iron to maintain ambient oxygen at tolerable levels, then expanded and diversified, converting the iron to insoluble ferric oxides.In the absence of biological silica secretion, the contemporaneous hydrosphere was saturated with H 4 SiO 4 , whose continuing precipitation was favored by near neutral pH. Ferric oxides were intermittently added. The episodicity of the iron-rich bands suggests cyclical changes in procaryotic populations, or rates of supply of ferrous iron, or both. Mechanical differences between geochemically similar contemporaneous BIFs imply variations in turbulence and depth of water. Geochemically varying facies of the same age suggest variations in availability of O 2 . With advanced biological oxygen mediation, continuing segregation of metabolic carbon, and increasing supplies of oxygen, the oceans were depleted of iron to become saturated with O 2 , which thereafter evaded to the atmosphere, giving rise to continental red beds. Rare Paleozoic BIF seems to be related to local euxinic conditions and volcanic sources of iron, reminiscent of Archean deposits. The apparently late Proterozoic deposits of the Rapitan (north-western Canada) and Jacadigo (southwestern Brazil) beds remain enigmas.

Oxidation states of peroxidase.

Abstract: Five oxidation states of horseradish peroxidase, ferrous, ferric, Compounds I and II, oxy-ferrous, are known. Various reactions and plausible structures of these states are reported. Mechanisms of peroxidase-oxidase reactions are discussed in terms of the five oxidation states of the enzyme.

Genesis of Precambrian Iron-Formations and the Development of Atmospheric Oxygen

Abstract: The hypothesis is presented that about 3.5 billion years ago oxygen was stored chiefly in carbonate rocks, silicate rocks, and water. Sediments cycled in a reducing atmosphere. Iron cycled as ferrous iron and precipitated chemically as carbonate or silicate under the same general controls as calcium and magnesium. As time went on, and photosynthesis by procaryotic organisms occurred, ferric oxides were formed in the shallow waters of the iron-depositing basins, and sulfates were formed bacterially during weathering, even though little if any free oxygen may have been produced. Organic material in an amount equivalent to the number of moles of oxygen stored in sulfates or iron oxides accumulated, and a similar number of moles of carbonate minerals was converted to other compounds. As sediments cycled, degraded organic matter was re-eroded and redeposited; ferric oxides joined the clastic fraction of stream loads, and sulfates tended to remain as sulfates. Perhaps with the advent, some 2 billion years ago, of eucaryotic photosynthetic organisms, which release free oxygen (Cloud, 1972), and the diminution of reduced mineral reservoirs consuming oxygen or its equivalent, atmospheric oxygen began to rise. Eventually a level was reached that achieved equality between the amount of organic material weathered and oxidized and the amount of new organic material deposited as the residue of photosynthesis minus respiration, decay, and oxidation. At this stage no further accumulation of organic materials was possible, and an essentially stable cycling system was established, with no further growth of oxygen-consuming reservoirs. This condition grossly characterizes Phanerozoic time. It is suggested that a major factor in the change from "Precambrian-type iron-formations" to those typical of the Phanerozoic may have been the simple consequence of a change in the transport of iron from dissolved ferrous iron to ferric iron carried in the suspended load of streams.

The effects of ascorbic acid supplementation on the absorption of iron in maize, wheat and soya.

Abstract: Summary. The absorption of iron from three staple vegetables was measured by the red cell utilization method in iron deficient subjects. The food iron had been labelled with 55Fe by the hydroponic cultivation method. In addition, 59Fe was added with or without carrier iron in the form of ferric ammonium citrate, prior to cooking. The constant relationship reported by others between the absorption of the two isotopes was confirmed, suggesting that the extrinsic iron and the food iron were absorbed from a common pool. The addition of ascorbic acid to maize porridge before cooking significantly enhanced the absorption of both the intrinsic and the added iron. However, no effect was noted with soya biscuits or with whole wheat bread (100% extraction). Evidence was obtained that these differences were due to the oxidative destruction of the ascorbic acid by the high temperatures required for baking. If, therefore, a feasible method were found for supplementing vegetable foodstuffs with ascorbic acid and inorganic iron, nutritional benefit would only be anticipated with uncooked or boiled foods.

The Anodic Oxide Film on Iron in Neutral Solution

Abstract: The composition of the anodic passive oxide film on iron in neutral solution has been investigated by cathodic reduction, chemical analysis and ellipsometry. The cathodic reduction using a borate solution of pH 6·35 containing arsenic trioxide as inhibitor estimates iron in the film to be all iron (III), indicating that no magnetite layer is present. Oxygen in the film is estimated from the ellipsometric thickness to be in excess of the stoichiometric ferric oxide, suggesting the presence of bound water. The average composition is represented as Fe2O3.0·4H2O, in which hydrogen may be replaced partly with iron-ion vacancy. The anodic oxide film is composed of an inner anhydrous ferric oxide layer, which thickens with the potential and an outer layer of hydrous ferric oxide whose thickness depends on the condition of passivation and environment. The anodic oxide film formed in the oxygen-potential region has also been measured by cathodic reduction, and it is found that the film retains nearly constant thickness above a critical potential where transpassive dissolution begins to occur.

Mayer's tannic acid-ferric chloride stain for mucins

Abstract: Tannic acid in aqueous solution is bound to mucins in formalin-fixed and formalin-free fixed tissues and its presence can be detected with ferric chloride as a dark gray, blue-black to black complex. This colored compound is readily extracted by acids and some chelating and bleaching agents and is changed to a reddish brown by alkalis. Hydrolysis in 1.2 N hydrochloric acid at 60#{176}C for 4 hr or hot trichloroacetic acid prevents the tannin-iron reaction. Acetyl chloride or bromide is able to inhibit the binding of tannic acid to the mucosubstances and saponification restores the characteristic reaction. Several mechanisms for the attachment of tannic acid to the mucins appear possible.

Iron-rich saponite (ferrous and ferric forms)

Abstract: Clayey fragments colored deep bluish-green are widely found in glassy rhyolitic tufts at Oya, Tochigi Prefecture. In room-air the color changes to black or gray within one hour and finally to brown in a few weeks. The fragments are composed of an intimate mixture of two kinds of smectite: a ferrous iron-rich smectite (IR) with bo : 9.300 ~; and an iron-poor smectite(lP) with bo = 9.030 A. Microscopic examination shows a vesicular texture and that IR occurs at the core and IP at the mar- ginal parts of each vesicle. Analysis by EPMA gave the following structural formulas: IR, (Na0,60- Ko.04Ca0.44) (Mg~.04Fe 2+ A1o02) (Sir.36All.64)O20(OH)4; IP, (Na0.~2K0.08Ca0.26) (Mgog0Fe2+.A1254) 3"98 " ' O'9a ' (SiT.66A1o.~4)O20(OH)4. IR has a much larger amount of iron in trioctahedral sites than that found in any earlier data. Acid-dissolution data, infrared absorption spectra, Eh-values, and DTA and TG curves are also given. Ferrous iron in the structure is easily oxidized in room air with loss of protons from the clay hydroxyls and with contraction of the lattice. We call the IR before and after oxidation the ferrous and ferric forms, respectively, of iron-rich saponite. They strongly suggest the existence of the iron- analogue of saponite. On exposed weathered surfaces in the field, brown fragments tend to be differ- entiated into two parts: one light yellow montmorillonite-beidellite; the other a brown incrustation due to hisingerite.

Evaluation of Crystallinity in Hydrated Ferric Oxides

Abstract: The nature of freshly-precipitated and aged hydrated ferric oxides prepared by the addition of ferric chloride to KOH was investigated by the use of scanning and transmission electron microscopy, X-ray diffraction, i.r. absorption, and pH 3·0 ammonium oxalate extraction. The results show the fresh material to be essentially non-crystalline hydrated ferric oxide, which when aged at 60°C C and high pH rapidly crystallizes as goethite, without any indication of coexisting hematite. The various methods were evaluated as indices of crystallinity for aging materials. The acid ammonium oxalate method was shown to extract selectively only the non-crystalline portion of such mixtures. The use of X-ray diffraction analysis for estimating aging stage requires elimination of the preferred orientation of the goethite crystals. While both the oxalate and X-ray methods can detect as little as 2 per cent crystallinity, the oxalate method is probably superior for quantitative determinations as it depends directly on an inherent difference in the solubility of the crystalline and non-crystalline materials, rather than on a technique dependent intensity measurement. The use of the intensity of the O-H bending vibrations of the infrared absorption spectra can also potentially detect as little as 2 per cent crystallinity, but the procedure is probably less useful for quantitative determinations than the oxalate or X-ray methods because of the problem of evaluating the area under the peaks.

Microbiological formation of basic ferric sulfates

Abstract: The iron-oxidizing bacterium Thiobacillus ferrooxidans was isolated from yellow-brown deposits found in soil, shale, metamorphic rock, and a uranium mine. In addition to the bacterium and pyrite, jarosite (K Fe3(SO4)2(OH)6), a basic ferric sulfate, was found to be present in the deposits. Oxidation of ferrous sulfate by the organism in liquid medium resulted in the formation of jarosite. On a solid medium of agar containing ferrous sulfate, ammoniojarosite (NH4Fe3(SO4)2(OH)6) was formed. Because jarosite can be synthesized at 25 C and 1 atm, it" is suggested that under natural conditions T. ferrooxidans plays a role in the formation of basic ferric sulfates.

Structure of Hemoglobin M Boston, a Variant with a Five-Coordinated Ferric Heme

Abstract: X-ray analysis of the natural valency hybrid α2+M Bostonβ2deoxy shows that the ferric iron atoms in the abnormal α subunits are bonded to the phenolate side chains of the tyrosines that have replaced the distal histidines; the iron atoms are displaced to the distal side of the porphyrin ring and are not bonded to the proximal histidines. The resulting changes in tertiary structure of the α subunits stabilize the hemoglobin tetramer in the quaternary deoxy structure, which lowers the oxygen affinity of the normal β subunits and causes cyanosis. The strength of the bond from the ferric iron to the phenolate oxygen appears to be the main factor responsible for the many abnormal properties of hemoglobin M Boston.

Method of extracting heavy metals from industrial waste waters

Abstract: A method is provided for extracting metal impurities from waste water to which ferrous ions are added to provide at least two times the amount of ferrous ions on the mol basis to the amount of metal ions present, the resulting solution containing acid radicals, a base being added to the solution to raise the pH to form a suspension of metal hydroxides, following which an oxidizing gas is bubbled in solution to form crystals containing ferric ions and further containing the metal ions originally in solution, the precipitated crystals being thereafter separated to provide clean water.

Oxidation of ferric porphyrins.

Abstract: Characterization of heme oxidation products falls naturally into two categories : species resulting from electron transfer, and in vivo and in vitro heme degradation products formed by oxidative addition or cleavage. In the former, we propose to include the intermediates appearing during the catalytic cycles of catalase (Cat), horseradish peroxidase (HRP), and cytochrome c peroxidase; the latter class consists of the bile pigments formed by catabolism of heme proteins as well as chemical intermediates such as oxophlorin and verdoheme. Salient features of the catalytic cycles of the enzymes have been discussed previously;' briefly, these are the appearance of a green species (compound I) when the enzyme is treated with HzOz or an organic hydroperoxide. The enzymatically active compound I is a two-electron oxidation product of the ferriheme protein and upon reduction forms first a one-electron oxidation product (Compound 11) which may be reduced further to the parent ferriheme. Compound I of cytochrome c peroxidase differs from these general observations inasmuch as its optical spectrum is quite similar to Compounds I1 of HRP and Cat and it displays an EPR2 signal at g 2.0. Although no EPR signal has been observed for HRP I or HRP 11, recent studies on the methyl hydroperoxide complex I1 of catalase show the existence of a complicated EPR spectrum. Other physical properties of interest are magnetic susceptibility measurements4 on Cat I and HRP I, which show that these species have an effective magnetic moment consistent with three unpaired electrons. The Mossbauer spectras-' of Compounds I and I1 of HRP and Cat have similar isomer shifts which, in turn, differ from those of the parent enzymes. A number of suggestions have been advanced concerning the chemical constitution, source of oxidizing equivalents, and electronic formulation of Compounds I

Aggregation of clay by the products of iron (III) hydrolysis

Abstract: An attempt has been made to discover the mechanism of iron cementation in clays by comparing the aggregation effected in dispersed pure mineral clay by its exposure to different stages in the active hydrolysis of a ferric chloride solution. Contact of the clay with the early products of the hydrolysis is apparently necessary for the achievement of stable bonding; clay mixed with the gelatinous precipitate formed at the end of the hydrolysis is not stably aggregated, but a combination of these two phases produces aggregates which are particularly resistant to normal dispersion treatment. The results are discussed in terms of the kinetic steps in the hydrolysis of iron(III) solutions, and their implications for structure formation in soils are outlined.

Nuclear Magnetic Resonance Studies of Ferric Porphyrins

Abstract: During the past five years there has been a great increase in the use of proton magnetic resonance spectroscopy (PMR) in investigating structure and structurefunction relationships in a variety of biological macromolecules containing paramagnetic metal Paramagnetism of the molecule can serve as a very sensitive and specific probe for the environment of the metal ion by causing large perturbations3 on the normal diamagnetic linewidths and chemical shifts of the protons. Since the interactions with the unpaired electrons are relatively short-range, only nuclei in the immediate vicinity of the metal ion are appreciably affected by the paramagnetism. If the exact origin of the proton-electron interaction is understood, considerable information on bonding and molecular configuration can be extracted from the linewidth and shift data. Although a variety of protein systems have been investigated by PMR,4-24 the two systems which have received the most attention and in which the technique has been most successful are the iron-sulfur p r ~ t e i n s ~ ' ~ * ~ such as ferridoxin, and the heme-iron proteins, cytochrome C , ~ I ~ the myoglobins,'3-20 and hemoglobins. 21-2 For the iron-sulfur proteins, PMR has been instrumental in e l u ~ i d a t i n g ~ * ~ ~ the antiferromagnetic coupling between irons in the twoand eight-iron species. For the heme-iron proteins, which are the systems of interest here, PMR data have proved valuable in the investigation of a variety of properties. Among the prominent examples of such studies are the detection of changes in tertiary and quaternary structure of hemoglobins, 21-23 the study of bonding, configuration and electron-transfer properties in cytochrome C , ~ O ' ' the probing of the environments of the iron in a number of myoglobins,13-19 and the location of magnetic axes within the porphyrin plane of myoglobin.20 The characteristic feature of the PMR spectra which facilitated these interpretations is that the paramagnetic (isotropic) shifts for the porphyrin and axial ligand protons are sufficiently large to move the peaks well outside the range of proton shifts commonly observed for analogous diamagnetic proteins,' i.e., 0 to -10 ppm from TMS. Although considerable useful information has been derived from these observed shifts, a clear understand-

Photostimulated oxidation of magnetite: 2. Mechanism

Abstract: It was demonstrated in an earlier paper that magnetite (Fe3O4) becomes oxidized upon exposure to UV radiation in O2-bearing atmospheres, and a set of kinetic constraints on the reaction mechanism was presented. In the present paper a model for the reaction mechanism has been derived that satisfies the constraints of the experimentally derived kinetic rate equation: (1) the protective oxide layer on the magnetite grain surfaces is disrupted by the action of absorbed H2O by promoting the migration of substrate cations to the surface; (2) the H2O desorbs from the magnetite grain surfaces, and atmospheric O2 molecules collisionally dissociate into adsorbed O atoms upon colliding with pairs of adjacent vacant adsorption sites; (3) upon illumination (λ ≤ 0.350 μ), electrons are photoejected from the magnetite, a portion of which attach to the physically adsorbed O atoms to form adsorbed O− ions; the capture of the electrons by the adsorbed O atoms results in the oxidation of Fe2+ ions to Fe3+ ions; (4) after S-O− formation a second photoejected electron attaches to form chemisorbed O2−; the chemisorbed O2− ions coordinate surface ferric ions to form ferric oxide; and (5) since the principal ferric oxide phase detected, i.e., hematite, has a more closely packed structure than magnetite, the ferric oxide layer fails mechanically (scale formation), exposing fresh magnetite grain surfaces for further photostimulated oxidation; as a result, photostimulated oxidation can proceed in the absence of additional adsorbed H2O.

Hydroxamate Recognition During Iron Transport from Hydroxamate-Iron Chelates

Abstract: Kinetics of radioactive iron transport from three structurally different secondary hydroxandate-iron chelates (schizokineniron, produced by Bacillus megaterium ATCC 19213; Desferaliron, produced by an actinomycete; and aerobactin- iron, produced by Aerobacter aerogenes 62-1) revealed that B. megateriurm SK 11 (a mutant that cannot synthesize schizokinen) has a specific transport system for utilization of ferric hydroxamates with a recognition capacity based on the chemical structure of the hydroxamate. Both Desferal and schizokinen enhanced iron uptake in this organism; however, Desferal-iron delivered only one-sixth the level of iron incorporated from the schizokinen-iron chelate. Desferaliron did not generate the rapid rates of iron transport noted with schizokinen-iron at elevated iron concentrations. Assays containing large excesses of either iron- free Desferal or iron-free schizokinen suggested that the iron-free hydroxamate may compete with the ferric hydroxamate for acceptance by the transport system although the system has greater affinity for the iron chelate. Aerobactin-iron did not stimulate iron uptake in B. megaterium SK 11 and aerobactin inhibited growth of this organism, indicating that B. megateriuni SK 11 cannot efficiently process the aerobactin-iron chelate. (auth)

Method of preparing ferrites

Abstract: A METHOD OF MAKING A MAGNETOPLUMBITE FERRIC CHLORRIDE IS VIDED WHEREIN AN AQUEOUS SOLUTION OF FERRIC CHLORIDE IS REACTED WITH AN ALKALI METAL HYDROXIDE TO FORM FERRIC OXIDE HYDRATE IN A SALT SOLUTION, AND THEN AN ALKALINE EARTH METAL CARBONATE IS ADDED TO THE MIXTURE. AFTER DRYING, THE FERRIC OXIDE AND THE ALKALINE EARTH METAL EARTH METAL CARBONATE ARE REACTED IN A MOLTEN SALT SOLVENT AND THE PARTICULATE FERRITE IS RECOVERED.

Oxidation of (E)- and (Z)-2,6-Dimethoxy-4-propenylphenol with ferric chloride–a facile route to the 2-aryl ethers of 1-Arylpropan-1,2-diols

Abstract: Oxidation of both (E)- and (Z)-2,6-dimethoxy-4-propenylphenol (3c) and (3d) with 1 equiv. of ferric chloride gives the 2-aryl ethers of erythro and threo 1-arylpropan-1,2-diols (1) and (2) (55%) which are formed by C-O coupling. The configurations of aryl ethers (1) and (2) were determined from p.m.r. and i.r. spectral data. Other products of the oxidation of phenol (3c) include the C-C-coupled 1-aryltetralin isomers (4) and the dihydronaphthalene (5), the 1-arylindane dimer (6), and 2,6-dimethoxy-1,4-benzoquinone. Oxidation of phenol (3c) with excess ferric chloride yields some oligomeric C-O-coupled material in addition to compounds (1) and (2).

Reduction of ferric phenanthroline--a procedure for determining serum uric acid

Abstract: A method for the determination of uric acid with ferric phenanthroline in a maleic acid buffer at pH 5.5 is presented. The procedure yields accurate (r2 = 0.96; recovery 99.3%) and precise (C.V. = 2.08%) results in 5 minutes, usually without deproteinization. The method appears to be more specific for uric acid than the reduction of alkaline phosphotungstate and compares well with uricase determination. Elevated ascorbic acid above 3 mg. per 100 ml. interferes.

Ferrous ferric oxides, process for preparing same and their use in magnetic recording

Abstract: Acicular ferrous ferric oxide crystals such as magnetite are prepared using a process which comprises mixing together aqueous solutions of a ferrous salt such as the sulfate or chloride and an alkali hydroxide such as NaOH or KOH to form a ferrous hydroxide precipitate as a dispersion, passing oxygen through the dispersion at 60 DEG C or lower to convert ferrous hydroxide particles to alpha ferric oxide hydrate crystals, discontinuing introduction of oxygen, boiling the dispersion to perfect crystallization of the alpha ferric oxide hydrate, dehydrating the alpha ferric oxide hydrate crystals to form alpha ferric oxide and reducing the alpha ferric oxide to form ferrous ferric oxide crystals.

Process for beneficiating a titaniferous ore and production of chlorine and iron oxide

Abstract: Chlorine and iron oxide are produced by the oxidation of iron chlorides and mixtures thereof, produced in the chloride process for beneficiating titaniferous ores, by injecting oxygen in the gas space above the fluidized bed. This void contains iron chloride when the ore is being beneficiated at a temperature of about 1,250* to 1,380* K. The oxygen and iron chloride form a partially oxidized mixture which is passed to a flue and cooled to about 1,025* K to complete the oxidation. The iron oxide and unreacted ferric chloride are recycled to the reactor.