NMR study of internal motions in certain iron group fluosilicates

NMR study of ferrous fluosilicate hexahydrate indicated the presence of motion of both proton and fluorine nuclei. Only a single narrow line was observed for protons for any arbitrary orientation of a single crystal with respect to the applied magnetic field. This can be interpreted in terms of a phase-correlated flip motion of the interproton vectors between two disordered orientations or in terms of a hindered rotation of the Fe(H2O) 6 octahedron about the fourfold axes, together with the flip motion. The fluorine second moment indicated that the SiF6 octahedron also is undergoing reorientation. The temperature variation of the powder linewidth showed a transition around 195°K and led to rather low values for the potential barriers hindering the motions. No significant temperature variation of the linewidth was observed for hexahydrated cobalt fluosilicate in the temperature range between 90°K and room temperature. Similar observations in a powder sample of tetrahydrated copper fluosilicate also showed the presence of internal motions. The linewidth transition in this case took place at about 220°K and was found to be rather abrupt. The potential barrier for the motion was found to be relatively high.

Composition of aqueous solutions in equilibrium with sulfides and oxides of iron at 3500°C

Solutions of potassium chloride (pH-buffered and 1-molat) equilibrated at 350°C with pyrrhotite, pyrite, and magnetite contained approximately 1 millimole of reduced sulfur and less than 0.1 millimole of oxidized sulfur per kilogram. Similar solutions equilibrated with pyrite, magnetite, and hematite contained approximately 1 millimole of reduced sulfur, but 3 to 6 millimoles of oxidized sulfur per kilogram. Both types of solutions contained less than 0.1 millimole of iron per kilogram at pH ≥ 6 and approximately 100 millimoles per kilogram at pH 2.

Control of nitrate reductase by iron in Neurospora crassa

Iron deficiency has been found to occur in Neurospora crassa grown in sole nitrate medium, even when levels of iron, normal with respect to the usual ammonium nitrate medium, were provided. Under this condition, mycelial nitrate reductase and catalase levels were high, there was inhibition of growth, and there was accumulation of an iron-binding compound and nitrite in the culture filtrate. These were counteracted by increasing the iron level of the sole nitrate medium, except that the catalase level increased still further. Evidence is presented for the control of nitrate reductase by iron.

Studies on iron metabolism in Neurospora crassa

Neurospora crassa Em 5297a secretes an ironbinding compound (X) when grown under conditions of iron deficiency. Decreasing the concentration of iron in the medium results in an increase of X and a corresponding fall in catalase activity. Under iron-deficient conditions the production of X precedes the fall in catalase activity. The iron complex of the iron-binding compound (XFe) can act as a good iron source to the organism to maintain normal growth and catalase activity, even though the iron is held very firmly in the chemical sense. While ferrichrome is as potent as XFe, as an iron source to N. crassa, ferrichrome A and ferric acethydroxamate are only partially beneficial. XFe, when provided as the sole iron source, also influences nonheme iron enzyme activities like succinic dehydrogenase and aconitase. XFe is permeable to N. crassa mycelia and is incorporated at a much faster rate compared with that from a simple chelate such as ferric citrate.

Some sulphoxide complexes of iron

Diphenyl sulphoxide(DPSO) and dimethyl sulphoxide(DMSO) complexes of iron(II) having the composition [Fe(DPSO)6](ClO4)2, Fe(DPSO)2Cl2, Fe(DPSO)3Br2, Fe(DPSO)4I2, [Fe (DMSO)3Cl2]. DMSO and [Fe(DMSO)3Br2]. DMSO and DPSO complexes of iron(III), Fe(DPSO)2 Cl3 have been prepared and their physico-chemical properties studied. Their magnetic moments at room temperature show them to be spin-free complexes. The i.r. spectra reveal that oxygen is the donor atom in all the complexes. The electronic spectra of iron(II) complexes indicate octahedral coordination for the metal ion. A salt like structure [Fe(DPSO)4Cl2][FeCl4], is suggested for the iron (III) complex, where the cationic species has distorted octahedral structure while the anionic species has tetrahedral structure.

An acid method for the volumetric estimation of water-soluble dithiocarbamates

Dithiocarbamates have been estimated previously by reaction with a strong acid, the carbon disulfide evolved being converted into a xanthate and the latter estimated iodimetrically. In the present method, a water-soluble dithiocarbamate is reacted with a decinormal mineral acid and the excess acid is determined to compute the amount of dithiocarbamate present. This method is applicable for the determination of a dithiocarbamate in a mixture containing thiuram disulfide.

Jodimetric estimation of water-soluble dithiocarbamates

Iodimetric estimation of dialkyl dithiocarbamate in alcoholic solution is not accurate. The method has not met with success for the water-soluble dithiocarbamates before. A simple and accurate iodimetric method has been developed for the estimation of water-soluble dithiocarbamates. The success of the method is due to the removal of the oxidation product which interferes during the titration with iodine.

Antipyrine and pyridine n-oxide complexes of iron(II)

Iron(II) complexes of 1-phenyl-2,3-dimethyl-5-pyrazolone (antipyrine, Apy) and pyridine N-oxide (PyO), having the formulae [Fe(Apy)6](ClO4)2, Fe(Apy)2Cl2, Fe(Apy)2Br2, Fe(Apy)4I2, [Fe(PyO)3Cl3]2 . 2H2O, [Fe(PyO)Cl2 . 2H2O]2, [Fe(PyO)3Br2]2 and [Fe(PyO)6]I2 have been prepared and characterized. [Fe(Apy)6](ClO4)2 in nitrobenzene and [Fe(PyO)6]I2 in acetonitrile behave as 1:2 electrolytes; Fe(Apy)4I2 shows considerable dissociation while Fe(Apy)2Cl2 and Fe(Apy)2Br2 are non-electrolytes and monomeric in nitrobenzene. [Fe(PyO)3Cl2]2 . 2H2O and [Fe(PyO)3Br2]2 in nitrobenzene and [Fe(PyO)Cl2 . 2H2O]2 in acetonitrile behave as non-electrolytes. All the complexes are spin-free. The i.r. spectra show that the oxygens of the CO and NO groups are the donors in the Apy and PyO complexes. A large decrease in the NO stretching frequency in [Fe(PyO)Cl2. 2H2O]2 suggests PyO acts as a bridge forming a binuclear complex. The chloro and the bromo complexes of Apy have been assigned pseudo tetrahedral structures while the rest of the complexes have octahedral or near octahedral configurations around the iron(II) on the basis of the magnetic moments and the electronic transitions.

4,4′-Bipyridyl complexes of iron: Magnetic, Mössbauer and other spectroscopic studies

4,4prime-Bipyridyl (4,4prime-bipy) complexes of ferrous salts of the Fe(4,4prime-bipy)x(anion)y type (where x or y=1 or 2) and of ferric salts of the Fe(4,4prime-bipy)m(anion)n type (where m=1 or 2 and n=3) have been synthesised. Elemental analyses, i.r. and electronic spectra, magnetic and Mössbauer studies have been performed to characterize the complexes. 4,4prime-Bipy and some anions are inferred to act as bridging ligands. The magnetic moments, electronic and Mössbauer spectra suggest that the complexes are of high spin type with distorted octahedral structures. The value of the isomer shift and quadrupole splitting are discussed in terms of bonding of the ligand and anions.

Biosorption of iron(III) from aqueous solutions using the husk of Cicer arientinum

Iron is a major pollutant released as a by-product during several industrial operations especially during acid mining of metal ores. In this paper, the use of Bengal gram husk (husk of channa dal, Cicer arientinum) in the biosorption of Fe(III) from aqueous solutions is discussed. Parameters like agitation time, adsorbent dosage and pH were studied at different Fe(Ill) concentrations. The adsorption data fit well with Langmuir and Freundlich isotherm models. The adsorption capacity (q(max)) calculated from the Langmuir isotherm was 72.16 mg of Fe(III)/g of the biosorbent at an initial pH of 2.5. Desorption Studies were performed at different concentrations of hydrochloric acid showing that quantitative recovery of the metal ion is possible. The infrared spectra of the biomass before and after treatment with Fe(III), revealed that hydroxyl, carboxyl and amide bonds are involved in the uptake of Fe(III) ions.