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Journal ArticleDOI

Studies on Mineralogical Properties of Vermiculites and Chlorites of Indian Origin

01 Jan 1982-Transactions of The Indian Ceramic Society (Informa UK Limited)-Vol. 41, Iss: 3, pp 78-81

AbstractMineralogical characterizations of some Indian vermiculites and chlorites are reported. Significant differences in X-ray and thermal properties are observed. Such anomalies of the properties are presumably due to presence of mixed layer minerals and/or other contaminations. more

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Abstract: The thermal decomposition reactions of some homoionic clay minerals, viz. vermiculite, in air in the temperature range 30°-1000°C by thermo-analytical methods are reported. The reaction kinetic of isothermal dehydration and dehydroxylation is found to obey first order reaction rate.

2 citations

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01 Jan 2014
Abstract: Soil chemical analysis , Soil chemical analysis , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

13,425 citations

Journal ArticleDOI
Abstract: The oxidation potential of dithionite (Na2S2O4) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na2S2O4 oxidized. Tests show that NaHCO3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline goethite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays. A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na2S2O4-citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was about 17 percent as contrasted to 35–80 percent with other methods.

3,637 citations

Journal ArticleDOI
Abstract: Vermiculite occurrences can be divided into two major categories, those having macro-scopic and those having microscopic or clay vermiculite. This paper is concerned with the former. The macroscopic type of vermiculite deposits can be subdivided into four categories based on the host rock: (1) ultramafic and mafic; (2) gneiss and schist; (3) carbonate rocks; and (4) granitic rocks. Field and laboratory evidence strongly suggests that most and possibly all macroscopic-type vermiculite deposits formed by the action of supergene solutions on biotite and phlogopite. Vermiculite in mixed-layer association with biotite, phlogopite, and chlorite is likewise believed to be of supergene origin.

47 citations