Showing papers on "Goethite published in 1978"
TL;DR: The influence of Al on the products formed by aerial oxidation at pH 5.5-7 and 20°C of Fe(II) chloride, sulfate and carbonate solutions, was examined in this article.
Abstract: The influence of Al on the products formed by aerial oxidation at pH 5.5-7 and 20°C of Fe(II) chloride, sulfate and carbonate solutions, was examined. In all cases Al at levels Al/Al + Fe = 0.09−0.30 inhibited the formation of y phases (lepidocrocite and maghemite) in favor of goethite under conditions where, in the absence of Al, these y phases formed. The influence of Al in these laboratory studies was supported by field observations.
99 citations
TL;DR: A series of mixed iron and titanium oxide coprecipitates ranging in composition between 0 ~ 0.7 with permanent and pH dependent negative charge were identified after aging NH3 coprecipes of Fe and Ti nitrate at 7WC and pH 5.5 for 70 days.
Abstract: A series of mixed iron and titanium oxide coprecipitates ranging in composition between 0 ~ 0.7) with permanent and pH dependent negative charge. Synthetic Ti-ferrihydrite and amorphous TiO2 were completely soluble in acid ammonium oxalate (2 hr extraction in the dark) whereas poorly crystalline anatase (width at half height, WHH > 2.0~ was partly oxalate soluble. NH4-oxalate soluble Ti was particularly high in soils developed under a cool montane climate (afro-alpine) and lower in soils of warmer subtropical climate, which contain anatase and futile. Several mixed Fe-Ti crystalline phases were identified after aging NH3 coprecipitates of Fe and Ti nitrate at 7WC and pH 5.5 for 70 days: (1) goethite and hematite in the composition range 0 < Ti/Ti + Fe ~< 0.20; at low Ti concentrations (<5 mole %) goethite was favored and/or hematite inhibited; (2) microcrystalline pseudorutile in the composition range 0.20 ~ Ti/Ti + Fe ~< 0.70; (3) anatase and ferriferous anatase in the range 0.70 ~< Ti/Ti + Fe < 1.0; with decreasing proportion of Ti the crystal- linity of anatase decreased. The results suggest that secondary or pedogenic Ti-Fe oxides can form by coprecipitation and crystallization in the weathering solution, and emphasize the essential role of water (as opposed to dry oxidation) in the alteration of primary titaniferous minerals.
54 citations
TL;DR: Mossbauer spectroscopy utilizing precise computer-based curve fitting procedures and X-ray diffraction methods have been used to study four deep-sea and one fossil marine manganese nodule.
Abstract: Mossbauer spectroscopy utilizing precise computer-based curve fitting procedures and X-ray diffraction methods have been used to study four deep-sea and one fossil marine manganese nodule. They have shown that X-ray amorphous goethite (α-FeOOH) and probably akaganeite (β-FeOOH) are the secondary iron oxidehydroxide phases present in the deep-sea nodules. The fossil nodule contained goethite with a larger particle size (approx. 350A) which had presumably been formed by the recrystallization of X-ray amorphous goethite and/or the alteration of the metastable akaganeite.
27 citations
TL;DR: Lepidocrocite was identified associated with mica particles and in the clay fraction of two well-drained Ontario soils developed on a granite and a granite-gneiss as mentioned in this paper.
Abstract: Lepidocrocite was identified associated with mica particles and in the clay fraction of two well-drained Ontario soils developed on a granite and a granite-gneiss. The occurrence of lepidocrocite is rare outside the tropics and there are no reports on its existence in well-drained soils.
18 citations
4 citations
01 Jan 1978
TL;DR: A review of the works on the hydrothermal synthesis of the crystals of some transition metal oxides is undertaken in this paper, where the process of obtaining the bulk crystals and the crystalline films are discussed.
Abstract: A review of the works on the hydrothermal synthesis of the crystals of some transition metal oxides is undertaken. The data on hydrothermal crystallization of magnetic oxides and the hydroxides of iron (hematite, magnetite, goethite, ferrites, garnets) as well as that of manganese and titanium are described in detail The process of obtaining the bulk crystals and the crystalline films are discussed.
3 citations
TL;DR: The heat of adsorption of water physically adsorbed on these pigments can be calculated from the measured heats of immersion of the samples both activated in vacuum (10 −5 mmHg) for 24 h at room temperature and in equilibrium with water vapour under conditions close to that required in order to obtain the statistical monolayer on the surface.
3 citations
Patent•
29 Jun 1978
TL;DR: In this article, it was shown that it is possible to obtain yellow hydrated iron oxide of fresh color useful for a yellow pigment, magnetic material, etc. by forming goethite nuclei in a high temp. and low pH range in a short time when an aq. ferrous salt soln is neutralized and oxidized.
Abstract: PURPOSE:To make it possible to stably obtain yellow hydrated iron oxide of fresh color useful for a yellow pigment, magnetic material, etc. by forming goethite nuclei in a high temp. and low pH range in a short time when an aq. ferrous salt soln. is neutralized and oxidized.
1 citations
Patent•
07 Nov 1978
TL;DR: In this article, a colloidal precipitate of Fe(OH)2 with air in a strong alkali soln was used to produce slightly branched needle goethite crystals.
Abstract: PURPOSE:To produce slightly branched needle goethite crystals by oxidizing a colloidal precipitate of Fe(OH)2 with air in a strong alkali soln. whose OH oncn. is specified.